UNITED STATES OF
AMERICA
FOOD AND DRUG
ADMINISTRATION
+ + + + +
CENTER FOR DRUG EVALUATION
AND RESEARCH
GASTROINTESTINAL DRUGS
ADVISORY COMMITTEE
+ + + + +
THURSDAY,
MARCH 6, 2003
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The
meeting was convened in the Ballroom of the Holiday Inn Gaithersburg, 2
Montgomery Village Avenue, Gaithersburg, Maryland, at 8:30 a.m., Michael
Camilleri, M.D., Acting Chair, presiding.
PRESENT:
MICHAEL CAMILLERI, M.D. Acting Chair
TOM PEREZ, M.P.H. Executive Secretary
SUSAN COHEN Consumer Representative
BYRON CRYER, M.D. Member
RONALD P. FOGEL, M.D. Member
JOHN T. LaMONT, M.D. Member
ROBERT A. LEVINE, M.D. Member
DAVID C. METZ, M.D. Member
MARIA H. SJOGREN, M.D. Member
CONSULTANTS (VOTING):
HOWARD McLEOD, PHARM.D.
RUTH HOFFMAN
MICHAEL PROSCHAN, Ph.D.
ZERUESENAY DESTA, Ph.D.
MEMBERS OF THE ONCOLOGIC DRUGS ADVISORY COMMITTEE
(VOTING):
DAVID KELSEN, M.D.
OTIS BRAWLEY, M.D.
FDA:
GARY DELLA'ZANNA, D.O., M.Sc.
FLORENCE HOUN, M.D.
VENKHAT JARUGULA, Ph.D.
ROBERT JUSTICE, M.D.
JOYCE KORBICK, M.D.
NARAYAN NAIR, M.D.
HUGO GALLO TORRES, M.D., Ph.D.
I‑N‑D‑E‑X
AGENDA ITEM PAGE
Call to Order, Introductions: 5
Michael
Camilleri, M.D., Acting Chair
Meeting Statement: 8
Thomas
H. Perez, M.P.H., Executive
Secretary
Opening Comments: 11
Robert
Justice, M.D., Director
Division
of Gastrointestinal and Coagulation
Drug
Products
Merck Pharmaceuticals Presentation 14
Introduction 14
Dennis
M. Erb, Ph.D.
Background and Rationale and
Clinical 20
Pharmacology
Kevin
J. Petty, M.D., Ph.D.
Clinical Efficacy 42
Kevin
J. Horgan, M.D.
Clinical Safety 71
Scott
Reines, M.D., Ph.D.
Summary and Conclusions 87
Scott
Reines, M.D., Ph.D.
Questions and Presentations 92
FDA Presentation 132
Clinical Summary 132
Gary
Della'Zanna, D.O., M.Sc., Division
of
Gastrointestinal and Coagulation Drug
Products
Biopharmacology Summary 149
Venkat
Jarugula, Ph.D., Clinical
Pharmacology
and Biopharmaceutics
Reviewer
Questions on Presentations 158
Open Public Hearing 182
I‑N‑D‑E‑X
AGENDA ITEM PAGE
Charge to the Committee 182
Robert
Justice, M.D., Director, Division
of
Gastrointestinal and Coagulation
Drug
Products
Discussion of Questions 184
P‑R‑O‑C‑E‑E‑D‑I‑N‑G‑S
(8:34
a.m.)
CALL TO ORDER,
INTRODUCTIONS
CHAIRPERSON
CAMILLERI: My name is Michael
Camilleri. I am the Acting Chairperson
for this Gastrointestinal Drugs Advisory Committee meeting. We are going to be discussing today the new
drug application, NDA 21‑549, on EMEND, which is aprepitant.
I
want to remind the board members, please, to speak directly into the microphone
and to remember to switch the microphone off when you are done with your
deliberations.
The
next item of business, really, is to invite the board members to introduce
themselves. So I would like to start.
DR.
HOUN: Hello. I'm Florence Houn. I'm the Office Director for FDA's Drug
Evaluation 3 Office. Thank you.
DR.
JUSTICE: Hi. I'm Robert Justice. I'm the Director of the Division of
Gastrointestinal and Coagulation Drug Products.
DR.
DELLA‑ZANNA: Hi. My name is Gary Della‑Zanna. I'm a medical officer in the Division of
Gastrointestinal and Coagulation Drug Products.
DR.
JARUGULA: Hi. I'm Venkhat Jarugula, clinical pharmacology
and biopharmaceutics on the NDA.
MS.
HOFFMAN: Hi. I'm Ruth Hoffman, patient advocate, National
Director of Candlelighters Childhood Cancer Foundation.
DR.
SJOGREN: Hi. I'm Maria Sjogren. I'm a gastroenterologist and
hepatologist. And I work at Walter Reed
Army Medical Center in Washington, D.C.
MS.
COHEN: I'm Susan Cohen. I'm the consumer member, and I just had a
colonoscopy.
DR.
FOGEL: Good morning. I'm Ron Fogel. I'm a gastroenterologist, division head at
Henry Ford Health System in Detroit.
DR.
CRYER: Good morning. I'm Byron Cryer, member of the
Gastrointestinal Drug Advisory Committee.
I am a gastroenterologist. I am
from the University of Texas, Southwestern Medical School in Dallas.
CHAIRPERSON
CAMILLERI: I'm Michael Camilleri. I'm a member of the Gastrointestinal Drugs
Advisory Committee. I am a
gastroenterologist. And I practice at
Mayo Clinic in Rochester, Minnesota.
SECRETARY
PEREZ: Tom Perez, Executive Secretary to
this meeting.
DR.
METZ: I'm David Metz. I'm at the University of Pennsylvania at
Philadelphia and on the advisory committee.
DR.
LEVINE: I'm Bob Levine from Syracuse,
New York at the Upstate Medical University, State University of New York. I'm a gastroenterologist and a hepatologist.
DR.
LaMONT: My name is Tom LaMont. I am from Beth Israel Deaconess Medical
Center in Boston. And I am a member of
the FDA committee.
DR.
KELSEN: David Kelsen, medical
oncologist. I'm from Memorial Sloane‑Kettering
in New York.
DR.
BRAWLEY: I'm Otis Brawley. I'm a medical oncologist at Emory University.
DR.
McLEOD: I am Howard McLeod, a clinical
pharmacologist in oncology at Washington University School of Medicine in St.
Louis.
DR.
DESTA: Zeruesenay Desta from Indiana
University, Division of Clinical Pharmacology.
I am a clinical pharmacologist and member of the advisory committee.
DR.
PROSCHAN: And I'm Mike Proschan. I am a statistician with the National Heart,
Lung, and Blood Institute.
CHAIRPERSON
CAMILLERI: Thank you very much. At this point I would like to turn the
proceedings over to the executive secretary for statements.
SECRETARY
PEREZ: Thank you.
MEETING
STATEMENT
SECRETARY
PEREZ: The following announcement
addresses the issue of conflict of interest with regard to this meeting and is
made a part of the record to preclude even the appearance of such at this
meeting.
Based
on the submitted agenda for the meeting and all financial interests reported by
the committee participants, it has been determined that all interest in firms
regulated by the Center for Drug Evaluation and Research which have been
reported by the participants present no potential for an appearance of a
conflict of interest at this meeting with the following exceptions.
Dr.
Byron Cryer has been granted waivers under 18 USC 208(b)(3) and under 21 USC
355(n)(4), an amendment of Section 505 of the Food and Drug Administration's
Modernization Act for ownership of stock in the sponsor valued at less than
$5,001 and for unrelated consultant for a competitor. Dr. Cryer receives less than $10,001 per
year.
Dr.
David Kelsen has been granted waivers under 18 USC 208(b)(3) and under 21 USC
355(n)(4), an amendment of Section 505 of the Food and Drug Administration's
Modernization Act for ownership of stock in the sponsor valued between $5,001
and $25,000.
Susan
Cohen has been granted waivers under 18 USC 208(b)(3) and under 21 USC
355(n)(4), an amendment of Section 505 of the Food and Drug Administration
Modernization Act for ownership of stock in the sponsor valued between $5,001
and $25,000.
Dr.
Camilleri has been granted a waiver under 18 USC 208(b)(3) for membership on a
competitor's advisory board through a contract with his employer. This interest generates less than $10,001 per
year.
Dr.
David Metz has been granted a waiver under 18 USC 208(b)(3) for his membership
on the sponsor's speakers' bureau. His
lectures generate income greater than $10,000 per year.
Dr.
Robert Levine has been granted a waiver under 21 USC 355(n)(4), an amendment of
Section 505 of the Food and Drug Administration Modernization Act for ownership
of stock in the sponsor valued at less than $5,001. Because this stock interest falls below the
de minimis exemption allowed under 5 CRF 2640.202(a)(2), a waiver under 18 USC
208 is not required. A copy of these
waiver statements may be obtained by submitting a written request to the
agency's Freedom of Information Office, Room 12A30 of the Parklawn Building.
In
the event the discussions involve any other products or forms not already on
the agenda for which an FDA participant has a financial interest, the
participants are aware of the need to exclude themselves from such
involvement. And their exclusion will be
noted for the record.
With
respect to all other participants, we ask in the interest of fairness that they
address any current or previous financial involvement with any firm whose
product they may wish to comment upon.
Thank
you.
CHAIRPERSON
CAMILLERI: Thank you, Tom.
I
would now like to invite Dr. Robert Justice to make his opening comments.
OPENING
COMMENTS
DR.
JUSTICE: Good morning. On behalf of the division, I would like to
take this opportunity to welcome the committee members and consultants to
today's meeting. We appreciate the time
that you are taking from your schedules to provide us with advice.
On
today's agenda is a new drug application for EMEND or aprepitant capsules
followed by a brief closed session later this afternoon. As you will hear, the new drug application
seeks approval for EMEND for the indication of EMEND in combination with other
*antiemetic medications. It is indicated
for the prevention of acute and delayed nausea and vomiting associated with
initial and repeat courses of highly emetogenic cancer chemotherapy, including
high‑dose cisplatin.
As
you listen to the company's and FDA's presentations, we would like you to keep
the following questions in mind for discussion this afternoon.
Go
to the first slide. The first one is,
has the aprepitant regimen been demonstrated to be effective in the prevention
of nausea and vomiting in the acute phase and in the delayed phase?
The
second question is, is the designation of "highly emetogenic
chemotherapy" appropriate given the regimens used in the clinical studies?
Next
question, please. The third question is,
can the recommended regimen be expanded beyond that used in the clinical
studies to include the use of any 5‑HT3 antagonist as part of
the aprepitant regimen? If not, what
additional studies would you recommend?
The
fourth question is probably the most important today. The preamble to that question is that
aprepitant is an inhibitor of the CYP3A4 metabolic pathway. For chemotherapeutic drugs that are metabolized
by this pathway, moderate inhibition of their metabolism could result in
serious or life‑threatening toxicity.
Next
slide. The first part of the question
is, the applicant has analyzed the safety data by chemotherapy regimen and a
significant number of patients received etoposide, vinorelbine, or paclitaxel,
which are substrates for CYP3A4, in combination with cisplatin and the
aprepitant regimen.
Is
this data sufficient to support the safety of aprepitant in combination with
these drugs? If not, what additional
studies would you recommend and should these studies be done pre‑approval
or post‑approval?
Next
slide. The second part of the question
is, few or no patients received docetaxel, vinblastine, vincristine,
ifosfamide, irinotecan, or imatinib, which are also substrates for CYP3A4, in
combination with cisplatin and the aprepitant regimen.
The
docetaxel drug‑drug interaction study has accrued only five patients to
date. Is there sufficient data to
support the safety of aprepitant in combination with these drugs? If not, what additional studies would you
recommend, and should these studies be done pre‑approval or post‑approval?
Next
slide. And, finally, does the committee
have specific concerns regarding potential drug‑drug interaction with
other chemotherapeutic agents or other drug classes? If yes, please discuss them and whether any
additional studies are recommended.
So
those are the questions to keep in mind.
With this introduction, I think we can hear the company's presentation.
CHAIRPERSON
CAMILLERI: Thank you.
Would
the company like to start?
MERCK PHARMACEUTICALS
PRESENTATION
INTRODUCTION
DR.
ERB: Good morning, Mr. Chairman, members
of the advisory committee, FDA, and ladies and gentlemen. My name is Dennis Erb from the Department of
Regulatory Affairs at Merck Research Laboratories. I am pleased to be here today to discuss
EMEND, Merck's trade name for aprepitant, for the prevention of chemotherapy‑induced
nausea and vomiting.
I
would like to provide a few introductory remarks before we present the results
from our development program. Over one
million cancer patients receive chemotherapy each year in the United States. Twenty percent are administered highly
emetogenic chemotherapy, the vast majority of which will experience an emetic
episode in the absence of antiemetic prophylaxis.
Patients
consistently report that nausea and vomiting are among the most distressing
side effects of chemotherapy. The
disruptive effects of these symptoms on patients' daily lives has been well‑documented
to the extent that patients may delay potential curative therapy because of
these symptoms.
No
single class of drugs is fully effective in preventing chemotherapy‑induced
nausea and vomiting. Current therapy
guidelines recommend a regimen consisting of a 5‑HT3 receptor
antagonist plus a corticosteroid. Despite
this use, greater than 50 percent of patients still experience nausea and
vomiting.
Even
with the advent of the 5‑HT3 receptor antagonist, delayed
emesis remains a serious problem with patients experiencing symptoms that often
last for several days following their chemotherapy.
In
light of the need for routine emetogenic use of chemotherapy, effective
prevention of nausea and vomiting remains an important goal of health care
providers and their patients. Thus,
there is a need for new therapies which can improve prevention of nausea and
vomiting and provide protection that lasts for several days.
EMEND
represents the first new approach in over a decade to address the significant
unmet medical need. It has a novel
mechanism of action by blocking substance P at the Neurokinin‑1 receptor
in the brain.
It
has a distinct efficacy profile, providing protection throughout the period
when symptoms may occur, both in the acute and in the delayed phases.
EMEND
also improves the effectiveness of current therapies, resulting in fewer
patients experiencing acute or delayed symptoms. Thus, the potential exists to alter an
enduring perception of cancer chemotherapy.
Nausea and vomiting need not be inevitable.
As
you have seen in the advisory committee briefing document and will hear about
today, the development program for EMEND provides compelling evidence to
support the use of EMEND in the prevention of chemotherapy‑induced nausea
and vomiting. Results from the clinical
program show that a regimen of EMEND given concomitantly with standard therapy
is effective in preventing nausea and vomiting due to highly emetogenic
chemotherapy.
Efficacy
was superior to that observed with standard therapy alone with significant
benefit in both the acute and delayed phases.
This advantage was maintained in subsequent cycles of chemotherapy.
Additionally,
this regimen was also effective in reducing the impact of these symptoms on
patients' daily lives. EMEND when added
to standard therapy also demonstrated a favorable safety profile that was
similar to standard therapy alone and has a drug interaction profile that is
well‑characterized.
The
presentation today will focus on the data supporting our new drug application
for the following indication. EMEND in
combination with other antiemetic agents is indicated for the prevention of
acute and delayed nausea and vomiting associated with initial and repeat
courses of highly emetogenic cancer chemotherapy, including high‑dose
cisplatin.
In
addition to our speakers, Merck has brought several consultants to the meeting
today. So they are available as a
resource to the advisory committee during discussions and deliberations.
Our
pharmacology consultants with us today are Dr. Paul Andrews, the St. George's
Hospital and Medical School; Dr. Merrill Egorin of the University of Pittsburgh
Cancer Institute; and Dr. Malcolm Rowland from the University of Manchester.
Our
statistical consultant, unfortunately, could not be with us today because of a
family emergency. Our clinical
consultants include Dr. Ronald De Wit of the Rotterdam Cancer Institute; Dr.
Steven Grunberg of the University of Vermont; Dr. Paul *Hesketh from Tufts
University School of Medicine; and Dr. Loren Laine from the University of
Southern California.
The
advisory committee members have previously received a briefing document from
Merck that provides more detailed information than time allows us to present
this morning.
The
outline for today's presentation is as follows.
First, Dr. Petty will provide background and rationale for the use of
Neurokinin‑1 receptors, antagonists for the prevention of chemotherapy‑induced
nausea and vomiting as well as review the clinical pharmacology data from our
program.
Dr.
Horgan will present the clinical efficacy information that supports the use of
EMEND in preventing nausea and vomiting due to highly emetogenic chemotherapy.
Following
Dr. Horgan's presentation, Dr. Reines will present the safety findings from our
development program and will summarize the evidence demonstrating that EMEND
represents a major advance in the prevention of acute and delayed nausea and
vomiting associated with highly emetogenic chemotherapy.
I
would now like to turn the podium over to Dr. Petty from the Department of
Clinical Pharmacology.
BACKGROUND AND RATIONALE AND
CLINICAL PHARMACOLOGY
DR.
PETTY: Good morning. This morning I will provide an overview of
the pharmacological properties of aprepitant.
The key points are summarized on this slide. I will first present data showing that
aprepitant has a novel antiemetic mechanism of action relative to currently
available antiemetic therapy in that it blocks substance P action via NK1
receptors in the brain. In both animals
and humans, unlike available therapies, it is effective in preventing both
acute and delayed chemotherapy‑inducted emesis.
Aprepitant
has a favorable pharmacokinetic profile that supports once daily oral dosing
and requires no dose adjustment in special populations, such as the elderly and
patients with renal or hepatic insufficiency.
The
background package provides a comprehensive description of the pharmacokinetics
and biopharmaceutics of aprepitant. It
describes several drug interaction studies with aprepitant that were conducted
during the course of this development program.
However, several of those studies were conducted to support the use of
aprepitant for chronic dosing indications.
And due to differences in dose levels or duration of a dosing of
aprepitant, they're not relevant to the short‑term dosing proposed for
prevention of chemotherapy‑induced nausea and vomiting.
The
studies relevant to administration of aprepitant for the proposed indication
will be presented here. And they
indicate that drug interactions with the aprepitant regimen for CINV are
generally modest and not clinically important.
Of particular importance is that aprepitant has a low potential for
interaction with chemotherapy, with which it would be co‑administered.
This
presentation will first provide a brief overview of the mechanisms of
chemotherapy‑induced nausea and vomiting.
Next, the pharmacological properties of aprepitant and its efficacy in
nonclinical models of chemotherapy‑induced emesis will be presented.
Finally,
I will review the clinical pharmacokinetics of aprepitant, which will include a
description of relevant drug interaction studies that were performed.
To
place the novel mechanism of action of aprepitant in context, I will provide a
brief overview of the mechanisms of chemotherapy‑induced nausea and
vomiting. There are both central and
peripheral mechanisms that contribute to the emetic reflex.
The
peripheral component involves effects of chemotherapy within the gut, in which
chemotherapeutic agents cause enterochromaffin cells to release serotonin. Acting locally, serotonin stimulates vagal
afferent nerves via 5‑HT3 receptors.
It
is at this level that 5‑HT3 antagonists primarily exert their
antiemetic effect. These afferents feed
into the brain stem, triggering emesis via activation of brain stem loci that
control the emetic reflex.
The
central component of CINV involves direct stimulation by chemotherapy of these
brain stem loci. Within the brain stem,
substance P facilitates the emetic reflex by activation of NK1
receptors. It is at this level that NK1
antagonists, such as aprepitant, exert their antiemetic effects.
Before
describing the antiemetic efficacy of aprepitant in animal models, I will
summarize some of the pharmacological properties of aprepitant. The properties of aprepitant can be
summarized as follows. First, there's an
antagonist for the substance P or NK1 receptor. Second, it binds specifically and with high
affinity to human NK1 receptors.
It is greater than *8,000‑fold selective for NK1
receptors over other receptors that mediate antiemetic activity, specifically
dopamine D2, serotonin 5‑HT3, corticosteroid, and
opiate receptors.
Animal
toxicology studies revealed no findings that preclude use of aprepitant in
humans.
In
the next few slides, I will present data that clearly demonstrate the
antiemetic effect of aprepitant on cisplatin‑induced emesis in ferrets, a
well‑established model that is used to assess antiemetic efficacy of
various compounds.
The
ferret models show pathophysiology of chemotherapy‑induced emesis that is
similar to humans. These models were
used in the discovery of the antiemetic effects of 5‑HT3
receptor antagonists. Since nausea
cannot be readily assessed in ferrets, the term "chemotherapy‑induced
emesis" is used, as opposed to "chemotherapy‑induced nausea and
vomiting" in humans.
The
ferret model has been used to characterize compounds or interventions that
induce emesis by either central or peripheral mechanisms. This slide lists various emetogens according
to the primary site of action, either central or peripheral, and qualitatively
summarizes the effects of either NK1 or 5‑HT3
antagonists.
In
these models, NK1 antagonists, such as aprepitant, are effective
against a broad spectrum of both central and peripheral emetogens; whereas, 5‑HT3
antagonists show a more limited spectrum of activity with efficacy mostly for
emetogens that exert their effects via peripheral sites of action.
Among
these emetogens, cisplatin is one of the most highly emetogenic agents
known. And it exerts its effect by both
central and peripheral pathways. Thus,
cisplatin‑induced emesis in ferrets has often been used to characterize
the efficacy of various compounds against highly emetogenic chemotherapy.
In
this model, ferrets were given a single intraperitoneal dose of cisplatin at
zero hour. And emesis was quantified
over the subsequent 72 hours. Vehicle‑treated
animals, shown in this graph, display the typical biphasic emetic response to
chemotherapy with an acute phase from 0 to 24 hours followed by a delayed phase
beyond 24 hours.
Aprepitant
given orally once daily at a dose of one milligram per kilogram provided
significant efficacy in both the acute and delayed phases of emesis in this
model, which was dose‑dependent, as shown by an even greater effect at a
dose of two milligrams per kilogram.
These results demonstrate that aprepitant with once daily oral dosing
provides significant protection against both acute and delayed cisplatin‑induced
emesis in ferrets.
In
other ferret experiments that I will not show here but are described in your
background package, it was confirmed that the antiemetic effect of aprepitant
required central NK1 receptor antagonism and that aprepitant
demonstrates additive efficacy with established antiemetic agents, specifically
dexamethasone or a 5‑HT3 receptor antagonist.
To
summarize its nonclinical efficacy, aprepitant is active against both the acute
and delayed phases of cisplatin‑induced emesis. And efficacy was observed with once daily
oral dosing.
In
the remainder of this portion of the presentation, I will focus on the human
pharmacology of aprepitant. Clinical
pharmacology studies show that once daily oral dosing provides acceptable
plasma concentrations of aprepitant in humans, which I will show on a subsequent
slide.
The
pharmacokinetics of aprepitant are not significantly affected by age, gender,
race, or body weight. And dose
adjustment is not necessary in patients with renal insufficiency or mild to
moderate hepatic insufficiency. As I
will show subsequently, aprepitant is brain‑penetrant and binds to NK1
receptors in the brain.
Shown
here is the plasma concentration profile of aprepitant in healthy subjects, who
receive the aprepitant CINV regimen 125‑milligram loading dose on day
one. Following the day two dose of 80
milligrams, the trough concentration was similar to that following the day one
dose. And the plasma concentration of
aprepitant after the last dose of 80 milligrams on day three was similar to that
on day one.
These
data show that the aprepitant three‑day regimen provides consistent daily
plasma exposure of aprepitant. During
the development program, a five‑day regimen was also studied in which the
80‑milligram doses were additionally administered on days four and
five. The five‑day regimen also
provided consistent daily plasma concentrations of *aprepitant.
Since
aprepitant exerts its effect in the brain, it was important to determine if
aprepitant reaches its intended target in humans. This was accomplished using positron emission
tomography, or PET.
Displayed
in the next few slides are the results of PET studies conducted with
aprepitant. For these studies, a
specific NK1 receptor binding tracer was developed. And the binding of the tracer in a human
brain is displayed in this PET scan.
Note that with this color scale, the blue color represents low binding
of the tracer; whereas, red represents the highest level of binding to NK1
receptors. These red areas correspond to
the corpus striatum, an area known to have a high concentration of NK1
receptors.
When
aprepitant was administered for two weeks to healthy volunteers, as you can see
in the lower PET scan, there was a high level of blockade of brain NK1
receptors after aprepitant dosing.
This
graph displays the relationship between aprepitant plasma concentration and
brain NK1 receptor occupancy determined approximately 24 hours after
the last dose of aprepitant. Each point
represents the result from an individual subject. Note that as plasma concentrations increase,
there is an expected increase in the level of brain NK1 brain
receptor blockade.
Superimposed
here is a crosshatched area that represents the mean with standard deviation of
plasma trough concentrations of aprepitant that are achieved with the three‑day
CINV regimen. Thus, this regimen is
anticipated to provide a high level of blockade of brain NK1
receptors.
In
the remainder of my presentation, I will provide an overview of potential drug
interactions with aprepitant. As I
mentioned previously, the potential for drug interactions with aprepitant was
well‑characterized in several clinical drug interaction studies, all of
which are described in your background package.
Studies
utilizing the regimen for CINV, which I will describe here, showed that the
aprepitant regimen for CINV generally has at most modest drug interaction
effects and that it has low potential for interaction with chemotherapy.
In vitro experiments indicated that aprepitant is
metabolized by cytochrome P450 3A4, an enzyme that metabolizes more than half
of all drugs. Thus, it was anticipated
that drugs that induce or inhibit CYP3A4 activity would affect the
pharmacokinetics of aprepitant. And this
was confirmed in clinical studies that I will not discuss here but are
described in your background package.
In vitro data also indicated that aprepitant inhibited
CYP3A4 activity, raising the possibility that it might affect other drugs
metabolized by CYP3A4. Therefore, it was
important to characterize the potential for aprepitant to inhibit CYP3A4 in vivo.
Orally
administered midazolam is a well‑characterized sensitive probe used to
assess the effects of drugs on CYP3A4 activity in vivo. It is possible to
rank the inhibitory effects of CYP3A4 of various drugs by their ability to increase
plasma concentrations of midazolam defined as the fold increase in midazolam in
plasma AUC.
This
slide shows a scale of strength of CYP3A4 inhibition going from weak on the
left to strong on the right. On this
scale, ketoconazole, one of the strongest CYP3A4 inhibitors known,
produces a 16‑fold increase in midazolam AUC. Generally, a two to five‑fold increase
is considered moderate inhibition and less than two‑fold increase is weak
inhibition. Other strong inhibitors are
itraconazole and clarithromycin.
Agents
considered moderate inhibitors include erythromycin, the calcium channel
blocker diltiazem, and verapamil, and grapefruit juice. The aprepitant five‑day regimen for
CINV on both the first and last day of dosing results in no more than moderate
CYP3A4 inhibition. And, thus, it
produces CYP3A4 inhibition comparable to grapefruit juice and widely used
drugs, such as diltiazem and verapamil.
Although
this degree of inhibition of CYP3A4 would not be expected to produce clinically
important interactions with most drugs, it was important to characterize
potential interactions of aprepitant with drugs with which it might be
frequently co‑administered. This
includes other antiemetics, such as the corticosteroids dexamethasone and
methylprednisolone as well as the 5‑HT3* antagonists
ondansetron and granisetron. Note that
all of these agents are metabolized to some extent by CYP3A4.
Also
investigated was the potential for aprepitant to affect the pharmacokinetics of
drugs with narrow therapeutic indices, including docetaxel, a chemotherapeutic
agent metabolized by CYP3A4; digoxin; and warfarin.
Note
that digoxin is a drug whose pharmacokinetics are dependent on P‑glycoprotein,
a membrane‑bound transporter that also plays a key role in the
disposition of many chemotherapeutic agents.
Thus,
evaluation of the potential effects of aprepitant on the pharmacokinetic of
docetaxel and digoxin provides a reasonable assessment of its potential to
affect the pharmacokinetics of several chemotherapeutic agents whose clearance
is dependent on CYP3A4 or P‑glycoprotein.
Described
first is the effect of aprepitant on dexamethasone, which was the
corticosteroid used in Phase III studies.
Shown here are plasma concentrations of dexamethasone in healthy
subjects on day one of a five‑day regimen in which a 20‑milligram
dose of dexamethasone was orally co‑administered with or without a 125‑milligram
dose of aprepitant. Co‑administration
of aprepitant resulted in an approximate two‑fold increase in the
dexamethasone AUC.
On
day five of the five‑day regimen, which included oral doses of eight
milligrams per day of dexamethasone and 80 milligrams per day of aprepitant.
There
was also an approximate two‑fold increase in dexamethasone AUC when co‑administered
with aprepitant. This effect of
aprepitant on dexamethasone served as the basis for reduction of the
dexamethasone doses in the aprepitant treatment arms in Phase III studies. This provided balanced exposure of
dexamethasone in the two treatment arms, which enabled evaluation of antiemetic
efficacy, not confounded by variable dexamethasone exposure.
Methylprednisolone
is also used frequently in antiemetic regimens and is metabolized by
CYP3A4. In this study, it was of
interest to evaluate the effect of aprepitant on IV‑administered
methylprednisolone since this route of administration is used frequently. Here methylprednisolone was administered as a
125‑milligram IV dose with and without the 125‑milligram loading
dose of aprepitant.
The
results showed a small, approximately 34 percent, increase in
methylprednisolone AUC. This indicates
that aprepitant had a weak inhibitory effect on IV‑administered
methylprednisolone. A minimal effect of
aprepitant on another IV‑administered CYP3A4 substrate was demonstrated
in a study using IV ondansetron.
Ondansetron
is the 5‑HT3 antagonist that was used in Phase III
studies. In this study ondansetron was
co‑administered to healthy subjects at the same dose used in the Phase
III studies, as a 32‑milligram IV dose on day one with a 375‑milligram
dose of aprepitant, which is three‑fold higher than the aprepitant dose
used in Phase III studies. As shown
here, there was little effect of aprepitant on plasma concentrations of
ondansetron .
Granisetron
is a 5‑HT3 antagonist also used in the treatment of CINV and
is metabolized by CYP3A4. Since this
drug might be co‑administered with aprepitant to prevent CINV, a separate
study was conducted in which granisetron was administered at a dose of 2
milligrams orally with a 125‑milligram dose of aprepitant on day one.
As
shown by the granisetron plasma concentrations in the right graph, there was no
significant effect of aprepitant on granisetron pharmacokinetics. From these studies, it is concluded that no
dose adjustments of ondansetron or granisetron are required when co‑administered
with aprepitant. These results also
indicated that moderate inhibition of CYP3A4 by aprepitant does not translate
into significant pharmacokinetic effects for some orally administered CYP3A4 substrates,
such as granisetron.
As
mentioned previously, chemotherapeutic agents with narrow therapeutic index
drugs and, thus, pharmacokinetic interactions with these drugs could
substantially alter their toxicities.
Cisplatin,
which was used in the Phase III studies, is not metabolized by CYP3A4 or other
CYPs. The pharmacokinetics of cisplatin
are unlikely to be affected by aprepitant since data indicate that the
potential for aprepitant to interact with chemotherapeutic agents would be via
CYP3A4. Since many chemotherapeutic
agents are metabolized by CYP3A4*, it is important to evaluate the potential
effects of aprepitant on a CYP3A4‑metabolized chemotherapeutic agent,
specifically docetaxel.
In
addition, the pharmacokinetics of several chemotherapeutic agents are modulated
by P‑glycoprotein. Thus, it was
also important to evaluate potential effects of aprepitant on P‑glycoprotein
activity using digoxin, which is a P‑glycoprotein substrate.
Finally,
warfarin is occasionally administered to cancer patients receiving
chemotherapy. And, therefore, the effect
of aprepitant on warfarin pharmacokinetics was evaluated.
Docetaxel
is an appropriate agent to assess the potential for aprepitant to affect the
pharmacokinetics of chemotherapeutic agents because it is metabolized
predominantly by CYP3A4 and it is also a P‑glycoprotein substrate.
In
this particular study, which is ongoing, patients receive the same IV dose of
docetaxel in each of two consecutive cycles given at least three weeks
apart. The pharmacokinetics of docetaxel
are assessed in each cycle.
In
one of the two cycles, the patients also receive the aprepitant regimen for
CINV in which the first dose of aprepitant is given one hour prior to docetaxel
infusion. In the other cycle, patients
do not receive aprepitant.
This
slide summarizes the data from the first five patients who have completed the
study. Shown on the left is a plot of
the mean plasma concentration profiles of docetaxel with and without
aprepitant. And on the right are the
docetaxel AUC values for each patient in both treatment cycles.
Note
that these curves are virtually superimposable and that the individual AUC
values are similar between treatment periods for each patient. This indicates that there was little, if any,
effect of aprepitant on docetaxel pharmacokinetics in these five patients.
To
assess the potential for aprepitant to affect P‑glycoprotein, healthy
subjects were doses to steady state with digoxin and were then administered the
aprepitant five‑day regimen for CINV.
Shown
here are plasma concentrations of digoxin with and without aprepitant on the
first day of the CINV regimen. There was
no significant effect of aprepitant on digoxin pharmacokinetics on day one or
at any other time point examined. It is
concluded that no clinically meaningful interactions with P‑glycoprotein
substrates are expected with the aprepitant regimen and that no dose adjustment
of digoxin is required when it is co‑administered with aprepitant.
To
summarize, the potential for aprepitant to affect the pharmacokinetics of
chemotherapeutic agents, it has been demonstrated that CYP3A4 and P‑glycoprotein
are common pathways that affect the pharmacokinetics of chemotherapeutic
agents.
We
have demonstrated that there is weak to no effect of aprepitant on IV‑administered
CYP3A4 substrates, including methylprednisolone, ondansetron, and the
chemotherapeutic agent docetaxel. We
have also demonstrated that there is no effect of aprepitant on a P‑glycoprotein
substrate.
Therefore,
we conclude that aprepitant has low potential to produce clinically meaningful
effects on the pharmacokinetics of IV chemotherapeutic agents. This conclusion is supported by safety data
from the Phase III studies that will be presented by Dr. Reines.
To
evaluate the effect of aprepitant on warfarin, a study was conducted in which
healthy subjects were titrated to constant low doses of warfarin followed by
administration of either the aprepitant three‑day regimen for CINV or
placebo.
Shown
here are the ratios of changes from baseline in trough plasma concentrations of
the two warfarin isomers: R warfarin and
S warfarin. These were measured during
and for several days after administration of aprepitant. And they reflect the effect of aprepitant
relative to placebo. There was a modest
34 percent reduction in S warfarin concentrations five days after completion of
the regimen with no meaningful effect on R warfarin.
The
decrease in S warfarin, which is metabolized by CYP2C9, was accompanied by a
small decrease in the international normalized ratio of the prothrombin time,
or INR. This is consistent with modest
induction by aprepitant of CYP2C9 activity, which was confirmed in a separate
study using tolbutamide as a CYP2C9 probe substrate. In that study, which is not shown here, a
modest CYP2C9 induction was returning to baseline by day 15, which is one week
beyond the last time point shown on this slide.
This small inductive effect on warfarin warrants closer monitoring of
the INR in patients taking warfarin.
In
summary, aprepitant has a novel antiemetic mechanism of action relative to
currently available antiemetic therapy by blocking substance P action via NK1
receptors in the brain. It is effective
in preventing both acute and delayed chemotherapy‑induced emesis in
ferrets.
Aprepitant
has a favorable pharmacokinetic profile that supports once daily oral dosing
and requires no dose adjustment in special populations, such as the elderly and
patients with renal or hepatic insufficiency.
The
potential for drug interactions with aprepitant has been well‑characterized. And drug interactions with the aprepitant
regimen for CINV are generally modest and not of clinical significance for most
drugs with which it would be co‑administered.
Pharmacokinetic
data as well as safety data from the clinical studies in patients receiving
chemotherapy indicate that aprepitant has a low potential for interaction with
chemotherapy with which it would be co‑administered.
In
conclusion, the pharmacokinetics of aprepitant and the potential for clinically
meaningful drug interactions with aprepitant have been well‑characterized. Appropriate guidance can be provided for safe
and effective use in the intended patient population.
I
will now turn the podium over to Dr. Horgan, who will present the efficacy data
from studies of patients with chemotherapy‑induced nausea and vomiting.
Thank
you.
CLINICAL
EFFICACY
DR.
HORGAN: Good morning. Chemotherapy characterized as highly
emetogenic evokes symptoms in the vast majority of patients in the absence of
preventive therapy.
Current
therapy to prevent symptoms consists of a combination of two agents: a 5‑HT3 receptor antagonist
and a corticosteroid. Despite this
therapy, at least 50 percent of patients still have symptoms of nausea and
vomiting when they receive highly emetogenic chemotherapy. Hence, there is an unmet medical need for
improved therapy. The clinical data we
will present demonstrates that aprepitant will help meet this medical need.
Nausea
and vomiting typically continue for several days following the administration
of emetogenic chemotherapy. A convention
is involved to delineate the time course of these symptoms. Early symptoms are referred to as acute and
later symptoms as delayed. In the
literature and in previous antiemetic programs, 24 hours after the
administration of chemotherapy has been the transition between the acute and
the delayed phases.
All
clinical studies that we conducted assessed efficacy in both phases with acute,
consistently defined as zero to 24 hours.
In more recent studies, particularly Phase III, we emphasized an overall
time frame, which is a merger of the acute and delayed phases, because of its
greater clinical relevance.
This
slide summarizes the basis for current therapy for prevention of symptoms
associated with highly emetogenic chemotherapy.
5‑HT3 receptor antagonists prevent symptoms, acute
symptoms, in approximately 50 percent of patients, though they have equivocal
efficacy in the prevention of delayed symptoms and are only approved for
prevention of acute symptoms.
Corticosteroids
augment the acute efficacy of 5‑HT3 receptor antagonists and
also have efficacy as monotherapy in the prevention of delayed symptoms. Though corticosteroids are recommended in
consensus treatment guidelines by the American Society of Clinical Oncology and
are extensively used in clinical practice, they are not approved for use as
antiemetics in the United States.
The
program objective was to define the potential role of aprepitant in the
prevention of nausea and vomiting associated with highly emetogenic
chemotherapy. The program followed the
development paradigm of agents previously approved for the prevention of the
symptoms of chemotherapy‑induced nausea and vomiting, notably the 5‑HT3
receptor antagonists.
The
program addressed three questions sequentially.
The first question, does aprepitant work alone as an antiemetic, as
implied by the preclinical data from the ferret model? A monotherapy study was done to answer this
question.
Next
we asked, is a regimen containing aprepitant more effective than current
standard therapy? Three studies were
done to answer this question. We will
present data from one of these studies, the one that provided the most pivotal
information. The data from the other two
studies are in your background.
Our
last question was, what was the optimum dose?
This was addressed by a single dose‑binding study.
Finally,
two studies were done to confirm that the Phase III regimen is effective and
safe. Before addressing these questions
specifically, I am going to spend a few moments providing a framework for
understanding the approach we took.
All
studies enrolled patients receiving cisplatin.
There were several compelling reasons why we focused on this patient
population. Cisplatin is a cornerstone
of current therapy for common cancers, such as lung and ovarian. Cisplatin is the most emetogenic
chemotherapeutic agent and has a predictable and well‑characterized
pattern of emesis lasting several days.
A
dose of cisplatin greater than or equal to 50 milligrams per meter2
is regarded as being highly emetogenic.
Cisplatin has been the benchmark chemotherapy for evaluation and
approval of novel antiemetic agents, notably the 5‑HT3
receptor antagonists ondansetron, granisetron, and dolasetron; and also the
dopamine receptor antagonist metoclopramide.
Efficacy
in the prevention of nausea and vomiting associated with cisplatin has
generally been predictive of efficacy in the prevention of symptoms associated
with other chemotherapeutic agents, such as carboplatin, doxorubicin, and
cyclophosphamide.
Some
important elements of the clinical trials we did included the following. All studies were double blind versus an
appropriate control. All patients
enrolled were cisplatin‑naive.
All
patients received high‑dose cisplatin infused over less than three hours
on day one. The cisplatin dose for
enrollment was greater than 70 milligrams per meter2 in all studies
except the initial study, when it was greater than 50 milligrams per meter2. Additional chemotherapy was permitted, though
additional emetogenic chemotherapy was only allowed on day one.
Randomization
was stratified for gender and additional emetogenic chemotherapy. Rescue therapy was allowed to treat
established nausea or vomiting.
A
daily patient diary was used to collect efficacy data. This included all emetic events, all use of
rescue therapy, and nausea assessments.
The primary efficacy analyses were focused on the first cycle of
chemotherapy and modified intention‑to‑treat populations.
Several
endpoints were assessed in order to comprehensively understand the efficacy
profile of aprepitant. The primary
endpoint in the majority of the studies and in both Phase III studies was
complete response. And the efficacy data
in this presentation emphasize this endpoint.
A
patient has a complete response if they have both no emetic episodes and also
do not take rescue therapy. Since rescue
therapy is permitted for emesis and nausea, this endpoint reflects control of
both emesis and nausea.
Complete
response was the primary endpoint for the 5‑HT3 receptor
antagonists ondansetron and dolasetron, which were both approved for the
prevention of chemotherapy‑induced nausea and vomiting.
Other
endpoints focused on emetic episodes, use of rescue therapy, and the impact of
nausea and vomiting on daily life.
And
so back to our questions. The first one,
does aprepitant work alone as an antiemetic?
This question was answered in a monotherapy study which used the
intravenous prodrug formulation of aprepitant, as explained in your background.
There
were two treatment groups. One received
a single dose of aprepitant intravenously and the other a single dose of
ondansetron, 32 milligrams, intravenously.
Both aprepitant and ondansetron were administered only on day one prior
to the administration of cisplatin.
A
placebo‑controlled group could not be included for ethical reasons. As based on historical data from the
literature, almost all patients receiving this dose of cisplatin will be
predicted to have emesis in the absence of therapy.
The
data during the acute phase and the delayed phase are shown. The vertical axis shows the percent of
patients with a complete response.
During the acute phase, both aprepitant and ondansetron had similar
efficacy. During the delayed phase, the
aprepitant‑treated patients had a much better outcome than those treated
with ondansetron. Forty‑eight
percent had a complete response versus 17 percent. And this difference was statistically
significant.
To
provide context, the dotted lines illustrate the anticipated response in the
absence of treatment based on historical data.
So this study provided very useful information. It showed that aprepitant is an effective
antiemetic clinically showing both the acute and the delayed phases. It also showed that aprepitant has a
distinctive efficacy profile relative to a 5‑HT3 receptor
antagonist with significantly superior efficacy in the prevention of delayed
symptoms.
The
distinctive efficacy profile of aprepitant implied that better efficacy might
be obtained by combining it with other antiemetics, such as a 5‑HT3
receptor antagonist. This possibility
provided the rationale for the next question we asked. Is a regimen with aprepitant more effective
than current standard therapy?
We
did three studies to answer this question and will present data from one of
these that was particularly helpful in establishing a rationale for subsequent
studies in the Phase III regimen. The
data from the other two are in your background.
I
would like to emphasize some important design features of this study. An aprepitant loading dose strategy was used
with a tablet formulation.
Patients
received aprepitant, 400 milligrams, on day one. And if treated on subsequent days, they
received 300 milligrams of aprepitant daily.
This day one loading dose was particularly high relative to the day one
dose ultimately selected for Phase III.
The
control group received a regimen that was consistent with standard clinical
practice at the time of the initiation of the study. This control regimen consisted of therapy on
day one only with both a single dose of a representative 5‑HT3
receptor antagonist, granisetron, and a single dose of a corticosteroid. Granisetron was administered intravenously
and dexamethasone orally.
The
design of the study is shown, the control regimen granisetron and dexamethasone
on day one only, placebo for aprepitant on day one and days two to five. Patients in the other two treatment groups
also received the components of the control regimen on day one with the
addition of aprepitant, 400 milligrams, on day one in both. One group received aprepitant on day one only. The other group received aprepitant on day
one and also on days two to five.
In
summary, three treatment groups, the control group receiving standard therapy,
one day aprepitant regimen, and a five‑day aprepitant regimen.
The
data during the acute and delayed phases are shown. The vertical axis again shows the percentage
of patients with a complete response.
During the acute phase, both aprepitant treatment groups were
significantly more effective than the control group. During the delayed phase, both aprepitant
treatment groups were also significantly more effective than the control
regimen. Also, the five‑day
aprepitant regimen was numerically more effective than the one‑day
regimen in the prevention of delayed symptoms.
We
concluded that aprepitant enhances the efficacy of a standard therapy regimen
during both the acute and delayed phases.
We also concluded that aprepitant is more effective when administered
for multiple days in the prevention of delayed symptoms, even when a very high
dose of aprepitant, 400 milligrams, is administered on day one.
Hinting
that continued dosing is more effective in the prevention of delayed symptoms
was also shown in the second study, the details of which are in your
background.
Based
on these conclusions and the data from the other studies that evaluated
different aprepitant regimens presented in your background, we then did a dose
finding study.
There
were several noteworthy design features of this study. The primary hypothesis related to overall
prevention of symptoms, "overall" meaning the entire five days
following the initiation of cisplatin therapy.
As mentioned before, the overall phase is affusion of the acute and
delayed phases and is favored because it is the most clinically relevant time
frame for the primary assessment of efficacy.
The
control group received a standard therapy regimen that consisted of therapy on
day one with both a 5‑HT3 receptor antagonist and a
corticosteroid followed by continued therapy with a corticosteroid,
dexamethasone, on subsequent days.
Instead
of chronicitron, a study previously, the 5‑HT3 receptor
antagonist selected was ondansetron.
Based on the very similar efficacy profiles of the various 5‑HT3
receptor antagonists, this change was not predicted to significantly alter the
efficacy profile of the aprepitant regimen.
There
was a transition to an aprepitant capsule formulation with improved
bioavailability. The aprepitant capsule
was used in all subsequent studies and is the formulation proposed for market.
The
dose finding study was initiated with two aprepitant regimens. The first was 375 milligrams on day one
followed by 250 milligrams on days 2 to 5.
The second was 125 milligrams on day one followed by 80 milligrams on
days 2 to 5.
After
initiation of the study, new data became available which demonstrated that the
aprepitant capsule formulation had even better bioavailability than
anticipated.
As
a result of this new information, it was predicted that both aprepitant
regimens would have similar clinical efficacy.
So in light of this, in order to adequately explore the aprepitant dose
response, the study was modified.
The
375/250 milligram regimen was discontinued after enrollment of 35
patients. The study was then resumed
with a new allocation schedule and new drug supplies and the addition of a
40/25 milligram aprepitant regimen. This
slide shows the design of the second part of the study after the modification
of the aprepitant treatment groups.
The
control regimen received ondansetron, the control standard therapy regimen,
ondansetron and dexamethasone on day one followed by dexamethasone on days two
to five. Patients in the other two
treatment groups received this standard therapy regimen, and both also received
a five‑day aprepitant regimen. The
first was aprepitant, 40 milligrams, on day one followed by 25 milligrams on
days 2 to 5. And the other was 125
milligrams on day one followed by 80 milligrams on subsequent days. The objective of the study was to assess the
aprepitant dose response.
The
data for the primary hypothesis overall complete response are shown. The vertical axis shows the percentage of
patients with a complete response. Both
aprepitant regimens were significantly more effective than the control regimen.
A
formal dose response analysis was done, which demonstrated that the 125/80
milligram regimen was significantly superior to the 40/25 milligram
regimen. The data during the acute phase
and the delayed phase are shown separately.
The 125/80 milligram aprepitant regimen was significantly more effective
than the control regimen during both the acute and the delayed phase; whereas,
the 40/25 milligram aprepitant treatment regimen was significantly more
effective than the control regimen during the delayed phase only.
This
Kaplan‑Meier curve illustrates the time to first emetic episode or rescue
over the five‑day evaluation period for the control group. The horizontal axis shows time over the
evaluation period of 120 hours. The
vertical axis, truncated at 40 percent, shows the percentage of patients with
no emesis or rescue. At time zero, the
time of initiation of cisplatin, 100 percent of the patients have had no emetic
episodes and have not taken rescue. At
120 hours, less than 50 percent of patients in the control group have had no
emetic episodes and have not taken rescue.
Few
patients are having more emesis or are taking rescue in the first few
hours. However, after approximately 18
hours, a substantial portion of the patients are having symptoms. Initial emetic episodes and use of rescue are
concentrated in the first 72 hours.
The
benefit of addition of both dose regimens of aprepitant is clearly seen with
the 125/80 milligram regimen superior to the 40/25 milligram regimen.
Initial
emetic episodes and use of rescue are also concentrated within the first 72
hours with the addition of aprepitant.
This display shows the data from the 375/250 milligram regimen
superimposed. As predicted, the outcome
in the patients in the 375/250 milligram regimen and the 125/80 milligram
regimen was very similar.
The
conclusions from the dose finding study were that the aprepitant 125/80
milligram regimen is effective. The
40/25 milligram aprepitant regimen was less effective. And the 375/250 milligram aprepitant regimen
added little or no benefit relative to the 125/80 milligram regimen.
Almost
all initial therapy failures occurred within 72 hours, implying that 3‑day
dosing with aprepitant would provide full benefit. Based on these conclusions, we proceeded to
Phase III in order to confirm the effectiveness and safety of a 3‑day
aprepitant regimen, 125 milligrams administered on day one followed by 80
milligrams administered on days 2 and 3.
The
Phase III hypothesis was compared to standard therapy, the aprepitant regimen
will provide superior control of nausea and vomiting as measured by the
proportion of patients with an overall complete response. That is, no emesis and no rescue in the 120
hours following the initiation of cisplatin.
In
order to rigorously assess this hypothesis, two Phase III multinational studies
were done with multiple‑cycle extensions.
These studies enrolled over 1,000 patients and were 2 of the largest
antiemetic trials with multiple‑cycle extensions ever done in this
patient population: cancer patients
treated with high‑dose cisplatin.
The
aprepitant regimen was refined for Phase III.
Aprepitant was dosed for three days, as I mentioned previously. The dexamethasone dose was reduced in the
aprepitant treatment group. So the
plasma dexamethasone levels would be similar in both treatment groups.
The
Phase III study design. Two treatment
groups; the control therapy regimen, ondansetron and dexamethasone on day one
followed by dexamethasone on days two to four.
Patients
in the aprepitant treatment group received this standard therapy regimen with
the refinement that the dexamethasone dose was reduced relative to the control
group. On day one, the control group
received 20 milligrams dexamethasone; whereas, the aprepitant group received 12
milligrams. On days two to four, the
control group received 16 milligrams of dexamethasone daily; whereas, the
aprepitant group received 8 milligrams daily.
The
key inclusion criteria were administration of high‑dose cisplatin,
greater than 70 milligrams per meter2 on day one. Exclusion criteria included significant
elevations of liver function tests, AST, ALT, and bilirubin, reduced renal
function, and reduced neutrophil and white blood cell counts, as shown. The concomitant or very recent use of strong
CYP3A4 inhibitors or CYP3A4 inducers were also precluded.
The
treatment groups were similar in terms of gender, age, and additional
emetogenic chemotherapy, as seen in the data combined from both studies. These are all risk factors for the
development of nausea and vomiting.
The
primary cancer diagnoses were similarly distributed between the treatment
groups, data combined from both studies.
The vast majority of patients in the studies, around 95 percent,
received concomitant chemotherapy in addition to cisplatin.
The
frequency of concomitant therapy with specific chemotherapeutic agents was
similar in both treatment groups. The
efficacy data for the primary endpoint of overall complete response are shown
for the first Phase III study, protocol 052.
Fifty‑two
percent of the patients in the control group had a complete response versus 73
percent in the aprepitant group, an increment of 21 percentage points, which
was highly significant, p less than
.001.
The
outcome in the second Phase III study, protocol 054, was strikingly
similar. Forty‑three percent of
patients had a complete response in the control group versus 63 percent in the
aprepitant group, an increment of 20 percentage points, which was also highly
significant, p less than .001.
Thus,
the primary analysis in both studies showed a consistent advantage for the
aprepitant regimen in the overall prevention of nausea and vomiting associated
with highly emetogenic chemotherapy, which was highly significant.
The
efficacy data for the key secondary endpoints of complete response during the
acute and delayed phases in both of the Phase III studies are shown. Both studies showed a consistent advantage
for the patients treated with the aprepitant regimen during both the acute and
the delayed phases when analyzed separately.
The differences were also of similar significance in both studies with p values consistently less than .001.
These
Kaplan‑Meier curves illustrate the time to first emetic episode or rescue
for the treatment groups over the five‑day evaluation period in both
Phase III studies. The advantage
provided by the addition of aprepitant throughout the acute and delayed phases
was clearly replicated in both studies and was statistically significant.
The
efficacy data for the endpoints of no emesis and no rescue overall are shown
for both studies. These endpoints are
the individual components of the primary endpoint of complete response.
Both
studies show a consistent advantage for the patients treated with the
aprepitant regimen for both the no emesis and no use of rescue therapy
endpoints. The efficacy of the
aprepitant regimen is, thus, supported by both components of the primary
endpoint. The greater use of rescue
therapy in the control group is particularly important to bear in mind in the
context of the assessment of the control of nausea, which I will now discuss.
Nausea
is a particularly important symptom for patients, which frequently occurs in
conjunction with vomiting. Though our
primarily assessment of the efficacy of aprepitant was in the prevention of the
syndrome of chemotherapy‑induced nausea and vomiting, we also carefully
assess nausea prevention independently.
The
assessment of nausea is more complex than either the assessment of emetic
events or use of rescue therapy because of its subjective nature. Nausea was assessed daily by patients using a
validated 100‑millimeter visual analog scale. The scale was anchored by zero millimeters
representing no nausea and 100 millimeters representing nausea as bad as it
could be.
Patients
placed a vertical mark daily on the scale corresponding to their level of
nausea in response to the diary question, "How much nausea have you had
over the past 24 hours?"
Two
pre‑specified nausea endpoints were analyzed with data from the daily
visual analog scale readings: no nausea
and no significant nausea. No nausea was
defined as a maximum rating of less than five millimeters on each day during
the overall five‑day assessment period.
This
definition of no nausea was also used by the most recently approved 5‑HT3
receptor antagonist, dolasetron. No
significant nausea was defined as a maximum rating of less than 25 millimeters
each* day during the overall 5‑day assessment period. This definition of no significant nausea
correlates with nausea that does not interfere with daily activities. The efficacy data for the pre‑specified
secondary endpoints of no nausea and no significant nausea are shown for both
studies.
Both
studies showed a consistent numerical advantage for the aprepitant regimen for
both nausea endpoints, though, as I mentioned before, it is important to bear
in mind that rescue therapy was most frequently used in the control group.
Statistical
significance was achieved for the no nausea endpoint in protocol 054. To explore further the control of nausea, the
data from both studies were merged in post hoc analyses of both nausea
endpoints and are shown.
Statistically
significant advantages for the aprepitant‑treated patients for both
endpoints were seen in these merged post hoc analyses. These data show that the addition of
aprepitant consistently improves the control of nausea associated with highly
emetogenic chemotherapy.
Other
pre‑specified endpoints were also studied. These included the composite endpoints,
complete protection, and total control.
Complete protection is defined as complete responses plus no significant
nausea; that is, no emesis, no rescue, plus no significant nausea.
Aprepitant
was significantly superior to control in both Phase III studies in terms of
complete protection. And the data is in
your background. Total control is
defined as complete responses plus no nausea; that is, no emesis, no rescue,
plus no significant nausea.
Aprepitant
was significantly superior to control in protocol 054 in terms of total control
and numerically better in protocol 052.
The data for total control are in your background.
Symptom
relief alone may not fully describe the benefits of effective antiemetic
therapy to patients because it does not assess the impact of nausea and
vomiting on patients' daily lives. So we
assessed the impact of nausea and vomiting on daily life using a validated
nausea and vomiting‑specified questionnaire.
The
questionnaire has two domains: an emesis‑specific
domain and a nausea‑specific domain.
Using the overall score derived from the questionnaire is a pre‑specified
analysis, aprepitant was significantly superior to control in both Phase III
studies in terms of impact on daily life, as detailed in your background.
The
data derived from the individual emesis and nausea domains, which are not
present in your background, were also supportive of aprepitant's benefit to
patients. In order to assess the benefit
of aprepitant in patients receiving a particular emetic regimen, we did a post
hoc efficacy analysis in the subset of patients treated with both cisplatin and
additional emetogenic chemotherapy, specifically cyclophosphamide and/or
doxorubicin.
Predictably,
the complete response was very low in the control group because of the more
intense emetic stimulus, only 26 percent of patients having a complete
response. The advantage provided by
addition of aprepitant was 33 percentage points, more than twice the response
in the control group, and a very substantial therapeutic effect in these
patients that was highly significant.
I
would like to briefly summarize the aprepitant cycle 1 efficacy data. The aprepitant regimen was effective in two
replicate clinical trials. Overall, 20
percent fewer patients vomited or required rescue medications for established
nausea or emesis, a p less than .001,
in both studies.
The
superiority of aprepitant was evident in both the acute and delayed phases for
both components of the primary endpoint:
emesis and the use of rescue medications. The superiority of aprepitant was also
evident in patients taking cisplatin plus other emetogenic chemotherapy. There was a consistent advantage to the
aprepitant regimen on both nausea endpoints, and it's important to bear in mind
in considering the nausea data that more rescue medications were used in the
control group in both *studies.
All
of the efficacy data we have presented has related to cycle 1 of
chemotherapy. Since cancer patients
typically receive multiple cycles of chemotherapy treatment, the assessment of
antiemetic efficacy during those multiple cycles is important.
The
vast majority of antiemetic studies have only collected cycle 1 data. And those that have collected multiple‑cycle
data have frequently been open label studies.
The
interpretation of data from multiple‑cycle extensions is complicated
because of the high attrition rate in this patient population and the potential
for bias when observing a subset of the cycle 1 patients. Both Phase III studies incorporated multiple‑cycle
extensions.
Patients
could receive the same blinded therapy they received in cycle 1 in up to five
additional cycles. Sixty‑eight out
of 71 study sites participated in the optional multiple‑cycle extension.
Data
collection was streamlined, and patients were simply asked to provide
"Yes" or "No" responses to two questions posed at the day
six to eight clinic visit, "Have you had any episodes of vomiting or
retching since your chemotherapy started in this cycle?" and "Have
you had any nausea since your chemotherapy started in this cycle that
interfered with normal daily life?"
The
observed proportion of patients without emesis and significant nausea are shown
during each of the multiple cycles two to six.
Data was combined from both Phase III studies. A consistent advantage is seen for the
patients receiving the aprepitant regimen, which appears to be maintained
throughout repeat cycles for those patients continuing in each of the multiple
cycles.
Another
way to evaluate the multiple‑cycle data is the time to first emesis and
the time to first significant nausea during the extensions. Data from both studies are combined and are
shown using a Kaplan‑Meier approach.
A
consistent advantage for the patients receiving the aprepitant regimen in terms
of emesis‑free time and significant nausea‑free time appears to be
maintained throughout repeat cycles for those patients continuing in the
extension, though the advantage is not as pronounced for the no significant
nausea endpoint compared to the no emesis endpoint.
In
summary, we performed two large Phase III studies to demonstrate that the
addition of aprepitant to a regimen of a 5‑HT3 receptor
antagonist and a corticosteroid is beneficial in the prevention of nausea and
vomiting due to highly emetogenic chemotherapy.
The
benefit is clinically important, is evident during both the acute and the
delayed phases, and appears to be sustained during multiple cycles of
chemotherapy.
My
colleague Dr. Scott Reines will now present the safety profile of receptor antagonist
and complete our presentation. Thank
you.
CLINICAL
SAFETY
DR.
REINES: Good morning. I would like to review with you the key
safety findings from the aprepitant clinical development program, which
included over 3,000 subjects and patients treated with aprepitant. Over 1,400 of these patients received
aprepitant for the prevention of nausea and vomiting associated with highly
emetogenic chemotherapy.
The
background document summarizes the safety of aprepitant across these
populations. Of note is the low inherent
toxicity of the drug documented in studies in non‑cancer patients in
which aprepitant, even at very high doses for up to eight weeks, was associated
with few adverse events.
My
presentation this morning will focus on the safety of aprepitant in the Phase
III clinical trials in cancer patients, protocols 052 and 054, which utilize
the 3‑day antiemetic regimen for which approval is being sought.
Initially
I will discuss cycle 1 of chemotherapy and then briefly review safety during
administration of aprepitant over multiple chemotherapy cycles.
Based
on its pharmacokinetic profile and our previous clinical experience, we
predicted that aprepitant would be very well‑tolerated in the antiemetic
regimen host for marketing. The Phase
III clinical trials confirm that prediction.
This
slide provides an overall summary of clinical adverse experiences during cycle
1 of the Phase III clinical trials. The
incidences of all clinical adverse experiences, those defined as drug‑related
are serious, discontinuations due to clinical adverse experiences, and death,
in the aprepitant and control groups are displayed.
The
incidences of all categories of adverse experiences are generally similar
between the treatment groups with the exception of adverse experiences defined
by the investigator as drug‑related, which were somewhat more frequent in
the aprepitant treatment group. The
difference was primarily attributable to small increases in drug‑related
hiccups, anesthenia, and fatigue, which were generally mild and trangient.
The
incidences of the most common serious clinical adverse experiences in the
aprepitant and control groups are displayed in this slide. Of note, the overall incidence of serious
clinical adverse experiences during cycle 1 is essentially identical in the two
treatment groups, 13.4 versus 13.6 percent.
No specific adverse experience occurred in more than 2.2 percent of
patients. And the incidences of specific
events were similar between groups.
Febrile
neutropenia occurred as a serious AE in 1.3 percent of patients in either
group. The spectrum of adverse events is
typical of cancer patients receiving chemotherapy.
My
next slide summarizes the Phase III chemotherapy cycle 1 laboratory adverse
experiences. The overall incidences of
all laboratory adverse experiences as well as those defined as serious or drug‑related
and discontinuations due to laboratory adverse experiences were generally
similar between the treatment groups during cycle 1 of the Phase III trials.
When
used in clinical practice, aprepitant will be administered with a variety of
concomitant therapies. During Phase III,
we sought to confirm the prediction based on clinical pharmacology data that
aprepitant would not have clinically important interactions with these other
medications.
We
approached the question in several ways, as illustrated here. Since all patients receive cisplatin,
potential renal and neurological effects, which are the dose‑limiting
toxicities with this agent, were carefully monitored. Cisplatin‑induced renal effects were
evaluated by analysis of serum creatinine.
And particular attention was paid to nervous system and ototoxicity.
Toxicities
of other types of chemotherapy, which were frequently administered in addition
to cisplatin, were evaluated by changes in neutropenia and other hematological
parameters as myelosuppression is the dose‑limiting toxicity for the
majority of these chemotherapies.
Other
common chemotherapy‑induced effects include fever, infection febrile
neutropenia, and dehydration. These
hematological parameters and clinical adverse experiences as well as those
indicative of potential glucocorticoid toxicity; that is, hypertension,
hyperglycemia, and hypokalemia, were pre‑specified as worthy of special
attention during Phase III.
In
addition, patients receiving chemotherapy metabolized, at least in part, by
CYP3A4, the enzyme responsible for aprepitant metabolism, were identified and
evaluated, both as part of the entire patient cohort and as separate subgroups.
Before
discussing the data on this slide, I would like to describe the way we
collected and evaluated adverse laboratory findings during Phase III. Laboratory data were to be collected for
analysis by a central laboratory during two clinically important time
windows. The first was day six to eight
following chemotherapy, when patients returned for clinical assessments,
including antiemetic efficacy.
At
this time, early toxic effects of chemotherapy may be identified. A later assessment was obtained between days
19 and 29, when patients are typically evaluated prior to a second round of
chemotherapy and when toxic effects, such as prolonged myelosuppression, can be
identified.
These
protocol‑mandated assessments were supplemented as needed by additional
measures that could be sent to local laboratories or to the central lab. The investigator was responsible for
assessing all laboratory data and recording as clinical or laboratory adverse
experiences any clinically significant findings.
Adverse
changes in laboratory and clinical parameters may be ranked according to
National Cancer Institute; that is, NCI, common toxicity criteria based on
their severity. The criteria established
four levels of increasing toxicity, grades 1 through 4.
All
of our data collected through the central laboratory were evaluated according
to NCI criteria. However, the local
laboratory data were not included in the NCI assessments.
This
slide depicts the incidences of any elevation of any serum creatinine in the
first line of the table followed by categorization of these elevations
according to the four NCI severity grades indicated in the left‑hand
column. The incidences of patients with
any elevation in serum creatinine were very similar between groups, both at the
earlier and the later time points.
More
than half of the early elevations had resolved my the later assessment. The NCI severity profile of changes was also
very similar between the groups at both time points. And no findings ranked in the most severe
category.
In
summary, there were no apparent differences in the nephrotoxicity of cisplatin
due to aprepitant as evidenced by the findings with serum creatinine. In addition, there were few neurological
adverse experiences and no differences between groups in terms of neurotoxicity
or ototoxicity.
As
discussed earlier, potential changes in the toxicity of non‑cisplatin
chemotherapies were assessed by evaluation of adverse reaction profiles typical
of these agents. For example, this slide
displays the occurrence of neutropenia in the aprepitant and control groups
overall and according to NCI toxicity criteria during cycle 1 of chemotherapy.
As
with creatinine and other laboratory parameters, blood counts for NCI
assessments were obtained during the day 6 to 8 and 19 to 29 time frames. Again, laboratory adverse experiences could,
nevertheless, be reported at any time in patients for whom additional local
laboratory studies were performed.
There
were no clinically important differences between the aprepitant and control
groups with respect both to overall incidences of neutropenia shown in the
first line of the table or to the incidences within each NCI severity
grade. There was slightly more
neutropenia in the control group at the day 19 to 29 assessment, but the
incidences of grades 3 and 4 neutropenia were essentially the same.
Unlike
the findings with creatinine, neutropenia was more common during this later
assessment period, reflecting the expected time course of changes in
hematological parameters following bone marrow suppression by chemotherapy.
The
data provided no evidence of differential chemotherapy‑induced toxicity
in the aprepitant group based on the similarities in neutrophil counts. A further assessment of the effects of
aprepitant on the toxicity of concomitantly administered therapies based on
occurrence of the pre‑specified adverse experiences discussed earlier is
shown on the next slide.
This
first group of adverse experiences, which includes infections, dehydration,
hematological toxicities, as well as fever and febrile neutropenia, reflects
chemotherapy‑induced adverse effects.
There were no clinically important differences between the aprepitant
and the control regimens.
The
second group of adverse experiences, reflecting potential dexamethasone or
corticosteroid‑induced toxicity, also occurred with very similar
frequencies in the two treatment groups.
In
summary, assessment of pre‑specified adverse experiences supports a lack
of significant interaction between aprepitant and concomitantly administered
chemotherapies or glucocorticoids.
Earlier,
Dr. Petty characterized aprepitant as a moderate inhibitor of CYP3A4 similar in
potency to diltiazem, which should not affect the toxicity of concomitantly
administered chemotherapy agents. We
sought to confirm this by evaluating the safety profile of aprepitant
separately in the subgroup of patients receiving chemotherapies that utilize
the enzyme CYP3A4 as at least one pathway in their metabolism.
The
relevant patients in our clinical trials received etoposide; the vinca alkaloid
vinorelbine; taxanes, including paclitaxel and to a smaller extent the **taxel;
and rarely irinotecan and ifosfamide.
Data assessed include clinical and laboratory adverse experiences and
hematological toxicities, in particular.
I
will review our neutropenia data in the entire subgroup of patients and
separately in patients receiving etoposide, vinorelbine, and paclitaxel, the
individual CYP3A4 metabolite chemotherapies most frequently administered during
Phase III.
Approximately
half of the patients in the Phase III trials received a concomitant therapy
metabolized by CYP3A4, as shown by the N's in this table. During cycle 1, the overall incidences of
adverse experiences were virtually identical, approximately 74 percent, in the
aprepitant and control groups in this subgroup of patients who received, in
addition to cisplatin, any concomitant chemotherapy metabolized by CYP3A4.
The
overall frequencies of pre‑specified adverse experiences indicative of
chemotherapy are glucocorticoid‑induced toxicity or serious adverse
experiences, also showed little difference between groups. There were no changes characterized as
serious laboratory adverse experiences in these patients.
My
next slide displays the occurrence of neutropenia graded according to NCI
toxicity criteria in patients who received chemotherapy metabolized by
CYP3A4. The incidences of neutropenia
during the earlier and later evaluation periods were generally similar in the
two treatment groups. There was a small
excess of neutropenia in the control group at the day 19 to 29 assessment,
primarily falling into the 2 milder NCI categories with no differences in the
more severe grades.
Based
on the incidence and severity of neutropenia at these two time points, there
was no change due to aprepitant in the hematological toxicity of chemotherapy
metabolized by CYP3A4.
This
slide depicts the frequencies of neutropenia of grade 2 or greater; that is,
less than 1,500 per millimeter3, in all patients who received CYP3A4
metabolized concomitant chemotherapy, shown on the left, this being the percent
of patients, and in those receiving the 3 most commonly administered individual
chemotherapies metabolized by this pathway.
Etoposide
was the most common. The N's are shown
at the bottom for each of these chemotherapies.
Substantial numbers of patients receive vinorelbine, the second most
common CYP3A4‑metabolized concomitant chemotherapy. And paclitaxel was also administered
frequently.
During
the cycle 1, day 19 to 29 assessment, which is a measure of prolonged and
clinically important myelosuppression, there were no noteworthy differences in
the occurrence of significant neutropenia among any of these patient subgroups.
As
noted, in addition to the NCI gradings of central laboratory data,
investigators were also instructed to record clinically important laboratory
findings as adverse experiences.
This
slide depicts all adverse experiences of neutropenia for the patients described
on the previous slides. As with the NCI
characterizations, the incidences of neutropenia adverse experiences also
showed no clinically important differences in the subgroups of patients
receiving any CYP3A4‑metabolized chemotherapy or in the individual
subgroups representing the three most frequently administered agents.
In
summary, during Phase III, we conducted an extensive evaluation of more than
250 patients per group, who received additional chemotherapy metabolized by
CYP3A4. We saw no pattern of clinically
important changes between the aprepitant and control regimens in these patients
based upon evaluation of overall and subcategories of clinical and laboratory
adverse experiences and of neutropenia, in particular.
In
addition to categorizing patients by whether they receive concomitant
therapies, we also evaluated standard patient demographic subgroups according
to age, gender, race, and primary cancer diagnosis. The data, which are presented in your
background package, support the conclusion that the aprepitant regimen has a
consistently favorable safety profile across these various demographic
subgroups.
Thus
far I have presented data describing our experience with aprepitant during an
initial cycle of chemotherapy. Cancer
patients typically receive initial followed by repeat cycles of chemotherapy. Therefore, the Phase III studies evaluated
aprepitant over multiple courses of chemotherapy, up to a total of six cycles
per patient.
During
multiple‑cycle extensions, patients continued on the same chemotherapy
and antiemetic regimens with which they were treated during cycle 1. Safety data collection during multiple cycles
included the most critical parameters according to investigators and
consultants and by prior agreement with FDA; that is, clinical adverse
experiences defined as drug‑related or serious, and those causing the
patient to discontinue further participation in the study. In addition, laboratory evaluations were
obtained at the day 19 to 29 visit.
A
large number of patients received treatment during multiple cycles. Over 400 patients in each group continued
beyond cycle 1 and approximately 150 patients were treated for a total of 6
cycles of chemotherapy in the aprepitant and control arms, as noted in the
safety update to the NDA.
The
safety findings over multiple cycles confirm the favorable profile observed
during cycle 1. This slide summarizes
the incidences of drug‑related or serious adverse experiences and those
associated with patient discontinuations as well as serious laboratory adverse
experiences and deaths. None of the
numerical differences between the groups was judged to be clinically
significant. And there was no pattern of
clinically important adverse events with the aprepitant compared to the control
regimen.
The
next slide illustrates the neutropenia observed during multiple cycles of
chemotherapy. The graph illustrates the
potential for aprepitant to affect the toxicities over time of concomitantly
administered chemotherapies based on the occurrence of neutropenia over the
course of six chemotherapy cycles.
The
bars display the percentage of patients with neutropenia of NCI grade 2 or
greater; that is, less than 1,500 per cubic millimeter at days 19 to 29. During each of the six cycles, the
percentages of patients with neutropenia were remarkably similar, indicating
that the hematological toxicity of concomitant chemotherapies does not change
over multiple‑cycle treatment with aprepitant. Overall, the adverse experience profiles and
laboratory data confirm that the good tolerability observed during cycle 1 with
aprepitant extends over multiple cycles of chemotherapy.
In
summary, the aprepitant regimen was well‑tolerated with incidences of
adverse experiences generally similar to standard therapy control. Aprepitant did not significantly alter the
toxicity of concomitantly administered cisplatin or other chemotherapy agents,
whether or not metabolized by CYP3A4.
And there was no evidence of increased glucocorticoid toxicity.
There
were no clinically important differences in the safety and tolerability profile
of aprepitant based on age, gender, race, or primary cancer diagnosis. And aprepitant was well‑tolerated
during multiple cycles of chemotherapy.
SUMMARY AND
CONCLUSIONS
DR.
REINES: I would like to conclude this
presentation to the advisory committee by sharing our perspective on the role
of aprepitant in the supportive care of cancer patients receiving highly
emetogenic chemotherapy.
When
patients are diagnosed with cancer, they are immediately confronted with the
reality of having a life‑threatening disease. Next, they must begin to consider the
prospect of undergoing treatments that may be debilitating and disruptive to
their lives at a time when they may not be physically impaired by the cancer itself. Clearly, at this time patients would like to
preserve their ability to function normally.
The symptoms of chemotherapy‑induced nausea and vomiting may
reduce their chances of doing that.
Since
1991, symptoms of highly emetogenic chemotherapy have been partially
preventable by use of 5‑HT3 receptor antagonists. These drugs were quickly recognized as
important therapeutic advances. However,
despite their use, many patients still experience nausea and vomiting after
emetogenic chemotherapy.
Patients
still rank nausea and vomiting among the most distressing symptoms caused by
chemotherapy. In particular, delayed
symptoms often occur when patients are at home following each cycle of
chemotherapy. And they remain difficult
to treat.
These
Kaplan‑Meier curves, which Dr. Horgan presented earlier today, illustrate
**patients in the control groups of our Phase III clinical trials. The curves show the percent of patients who
remain free of emesis and the need for rescue medication.
By
the end of day one, this proportion has already dropped below 70 percent. And after the five‑day observation
period following their chemotherapy, half or fewer patients in each control
group were fully protected, indicating additional loss of control during the phase
of delayed symptoms.
The
graphs clearly illustrate the need for better antiemetic therapy since all of
these control patients were treated with the best currently available
treatment: a combination of a 5‑HT3
antagonist and a corticosteroid.
Aprepitant
was developed to address this need. Over
the course of seven years, we studied more than 3,000 patients, including more
than 1,400 in cancer chemotherapy trials.
We chose to develop aprepitant as an essential component of an
antiemetic therapy regimen to be used in conjunction with other antiemetic
agents. In that way, we were able to
achieve unprecedented efficacy during both the acute and delayed phases
following highly emetogenic chemotherapy regimens.
The
efficacy of aprepitant observed during cycle 1 was sustained over multiple‑cycle
treatment. In all trials, aprepitant was
very well‑tolerated.
Safety
was demonstrated across a broad range of aprepitant doses in the presence of
various chemotherapeutic agents, in addition to cisplatin, and with two
different 5‑HT3 receptor antagonists. The overall safety and tolerability of a
three‑day aprepitant regimen was confirmed in the Phase III clinical
trials.
Returning
to the Kaplan‑Meier curves, which now also illustrate in yellow the
results for the aprepitant regimen, we can clearly see the marked clinical
efficacy observed in the Phase III development program.
More
than two‑thirds of the patients who received the aprepitant regimen were
protected from emesis or the need for rescue therapy over the entire five days
following their chemotherapy. This is a
marked advance over the current standard of care, again shown in blue.
The
effect of aprepitant begins within 24 hours during the acute phase of
chemotherapy and is especially pronounced in prevention of delayed symptoms
over the next four days.
In
conclusion, the aprepitant represents the first of a new class of therapy, a
Substance P antagonist at central NK1 receptors that features a
novel mechanism of action with distinct clinical benefits. As a cornerstone of a regimen for prevention
of nausea and vomiting due to highly emetogenic chemotherapy, aprepitant
provides marked symptom reduction and improves upon the best available
antiemetic therapy.
We
hope that this new medicine may alter an enduring perception of cancer
chemotherapy by allowing most patients to undergo emetogenic treatment without
the inevitable fear of nausea and vomiting.
We
are pleased to have had the opportunity to share our data with you this
morning. In closing, I would like to
leave you with our proposed indication for aprepitant. Thank you.
CHAIRPERSON
CAMILLERI: Thank you very much.
QUESTIONS AND
PRESENTATIONS
CHAIRPERSON
CAMILLERI: I would like to propose that
we spend about ten minutes now addressing some questions. I would like to thank the company
representatives for their very comprehensive and clear presentations to us.
And
I would like to propose to the committee members that in the first part of the
questions to the company we focus on issues that are not already entertained in
the brief that Dr. Justice provided us.
For example, I am sure we are going to come back later in the
presentations from the agency as well as perhaps questions this afternoon as we
discuss these several issues. We are
going to need to address the specific questions that you proposed pertaining to
efficacy in nausea and also the proportion of patients with other inducers of
cytochrome p450 3A4, which may not have been over‑represented in the
patient groups here.
So
I would like the committee members in this first part of the questioning to
focus on specific issues pertaining to the presentations we have just heard and
not the general issues that were entertained in Dr. Justice's opening
arguments.
So
the other thing I would like to do in the next 10 to 15 minutes before we
adjourn for a break is to try to focus the questions first on areas pertaining
to clinical pharmacology. Then we will
have the break. Then we will come back
and deal with clinical efficacy and safety issues.
So
if that is acceptable to **everyone ‑‑ and I am assuming it is ‑‑
I would like to ask my colleagues on the committee whether you have any
questions pertaining to pharmacology.
Perhaps we will address the questions on 3A4 and numbers, et cetera,
later, when we discuss this with the agency's presentation.
Dr.
LaMont?
DR.
LaMONT: Yes, sir. I have a question about figures 28 and
39. There seems to be no data provided
on figure 28 for aprepitant plasma between hour 24 and 48. Also, on slide 39, there is no data for days
2, 3, and 4, although you're giving the drug on those days. I just wonder why those data weren't included
or if they're soon to be unrevealing or ‑‑
DR.
PETTY: Actually, if I can answer the
question, if we could first go to slide number 28, please? In this particular study, the data actually
weren't collected. We did not collect
the detailed profile between 24 and 48 hours.
So the plasma samples that were collected were from zero to 24 hours the
first day of the regimen and from 48 to 72 hours the last day of the
regime. So there is not a detailed
plasma profile in between day one and day three.
DR.
LaMONT: Would you predict it would go
up?
DR.
PETTY: No. We would ‑‑
DR.
LaMONT: Would it exceed the p count day one?
DR.
PETTY: We think that would be unlikely
based on the effect that we see on day three.
We also observe with the longer dosing of the five‑day regimen
that the trough concentrations remain relatively constant.
And
if we could go to slide 39, I believe it was?
DR.
LaMONT: Thirty‑nine.
DR.
PETTY: Yes. And this experiment was conducted in a
similar fashion. The profiles for
dexamethasone were collected only on day one and day five, the first day and
the last day of the regimen.
CHAIRPERSON
CAMILLERI: Thank you.
Dr.
Metz?
DR.
METZ: Yes. Thank you.
I
noticed in that slide that was just shown right there that you reduced your
dose of the steroid for the therapeutic arm of your trial because of the
induction that occurs. Do you have any
data without steroids at all?
I
am interested in whether the effect on your delayed response is steroid‑mediated
because that is the proposed action of the steroids or whether you are just
boosting the effect of the steroids, you are lowering the dose but you are
getting your added effect that way. So
do you have any data at all without the steroids?
I
realize your program is designed to add to an existing regimen, but it seems to
me conceivable that you could have a regimen without a steroid, which in itself
has potential side effects.
DR.
PETTY: Well, for the effect that we see
here with dexamethasone, the approximate twofold increase, we adjusted downward
for the dose of dexamethasone to provide balanced dexamethasone exposure in the
Phase III studies. And the Phase III
studies were conducted with dexamethasone in both arms.
CHAIRPERSON
CAMILLERI: So, to clarify that point, I
think what Dr. Horgan is going to say is that the aprepitant‑treated dose
with steroid dose with the aprepitant group was lower than in the control
group. Is that correct?
DR.
PETTY: Correct. They're the same level.
DR.
HORGAN: Right. And just to clarify the background to your
question and how we approached it philosophically in the program, we did a
monotherapy study first, which clearly showed the efficacy of aprepitant in the
prevention of delayed symptoms without any confounding factors.
Then,
when we did a variety of Phase II studies, we studied aprepitant in the context
of concomitant corticosteroid therapy on day one. And we again consistently showed efficacy in
the prevent of delayed symptoms.
Then
when we moved into the latter part of the program, when it was clearly the
established standard of care and recommended, for example, in consensus
guidelines that corticosteroids be administered during the delayed phase, we
evaluated aprepitant in the context of addition to a standard therapy regimen.
Now,
it's correct. We did not define
precisely the relative contributions in the later part of our program provided
by aprepitant and dexamethasone in the prevention of delayed. However, we clearly demonstrated prior to
that that aprepitant has a substantial effect in the prevention of delayed
symptoms.
DR.
METZ: Except that you don't have any
data without steroids except for your monotherapy trial.
DR.
HORGAN: Right.
CHAIRPERSON
CAMILLERI: Dr. Desta?
DR.
DESTA: Yes. I have a question of whether you have
screened for CYP2C8 and 2B6 because CYP2C8, even though paclitaxel is
metabolized by 3A, there is also a component of 2C8. So at least the in vitro data must be done for this purpose, I guess.
And
the other one is CYP2B6. We know that
cyclophosphamide and partly absorbed ifosfamide, these drugs are primarily,
including thiotepa also, metabolized by 2B6.
I wonder whether we have some at least in vitro screening data for these isoforms.
The
second question I have is, you mentioned address does not affect the PK of your
drug. And I saw in one of the documents
that there is a several‑fold increase in AUC of aprepitant.
So
when do you say it is not clinically important in age, the group with, if I am
correct, a 74 percent increase in AUC?
Is that correct?
DR.
PETTY: You are referring to the effect
of other drugs on aprepitant?
DR.
DESTA: No, no.
DR.
PETTY: I'm sorry. I didn't ‑‑
DR.
DESTA: On age.
DR.
PETTY: Age? Oh, sorry.
Yes.
DR.
DESTA: Yes. And my last question is, you talk about the
exposure better, and you have shown PET data in your data analysis. I wonder whether you did some time course of
that because that will guide you probably to the dosing interval of the
drug. After a single dose, did you do
some sort of time course for the PET analysis?
DR.
PETTY: If I can answer your first
question first?
DR.
DESTA: Okay.
DR.
PETTY: You asked about effects,
potential effects, of aprepitant on CYP2B6 and CYP2C8.
DR.
DESTA: Yes.
DR.
PETTY: We have not specifically
evaluated those in our in vitro
screens of microsomal turnover, although we have evaluated, in addition to
CYP3A4, several other cytochrome p450 enzymes.
And there was no evidence of inhibition of aprepitant of those
cytochrome p450 enzymes. It exclusively
had an effect on CYP3A4.
So
specifically, no, we have not evaluated CYP2B6 and 2C8 in vitro, although our clinical data would suggest that there
doesn't appear to be a significant effect of aprepitant on drugs metabolized by
those enzymes.
For
your second question regarding age, we specifically looked at the potential
effects of age on the pharmacokinetics of aprepitant in a study in elderly
subjects as well as a comprehensive analysis of all of our Phase I data.
We
found very slight effects, at most perhaps a 30 percent increase in the AUC of
aprepitant. We have found that in our
clinical program, aprepitant is a rather wide therapeutic index drug. And, as Dr. Reines pointed out in some of our
other studies with higher doses of aprepitant given for much longer periods of
time, we found that plasma concentrations seven‑fold higher than those
achieved with this regimen have been very well‑tolerated. So we would conclude that a 30 percent
increase in AUC would not be clinically important.
And,
to answer your third question, with regard to the PET studies, no, we have no
specifically done single‑dose PET studies. Given the complexity of those studies, we
were essentially only able to measure the drug concentration and brain
occupancy effects at a single time point 24 hours after the last dose of
aprepitant. Based on a dose‑response,
the plasma concentrations clearly correlated very well with the brain
occupancy.
CHAIRPERSON
CAMILLERI: Dr. Cryer?
DR.
CRYER: Thank you.
This
is also for Dr. Petty. So one of the
questions which we will be focusing on is the potential for interaction of
aprepitant with chemotherapy, which is obviously similarly metabolized by
CYP3A4. So in that light, I would like
to go back to slide 44, if we could.
The
question is, as I understand it, these data are data with aprepitant with its
effects on docetaxel plasma concentrations.
And this **issue is in your application and clinical practice, it is
proposed to use aprepitant as combination therapy with the 5‑HT3
antagonists as well as with the corticosteroids. And so I really can't take this data and
generalize it to what we might expect to see in clinical practice.
So
do you have any data with the combined therapy of the three, the
corticosteroids, the 5‑HT3 antagonists, along with aprepitant,
with regard to its effects on chemotherapeutic agents that would be metabolized
by CYP3A4?
DR.
PETTY: Most of our drug interaction
studies have been done with aprepitant by itself to provide as clear a result
as possible. We know that the agents
that are co‑administered in the regimen, the 5‑HT3
antagonists and the steroids, do not inhibit CYP3A4 activity, for example. There is no evidence of that.
So
we would not anticipate a different type of interaction when the three agents
are used together, but typically the results that we see with aprepitant used by
itself are fairly consistent with that, at most a moderate effect on CYP3A4.
CHAIRPERSON
CAMILLERI: Dr. Fogel?
DR.
FOGEL: Thank you.
I
have a question about the central binding of aprepitant. The physiology related to vomiting indicates
involvement of the vagal complex in the area postrema. The PET studies that you showed on slides 29
through 31 show the cortex. And PET
scans aren't particularly effective in showing the vagal complex.
Do
you have any data regarding blinding studies looking at the effects of
aprepitant on NK1 receptors in the dorsal vagal complex and the area
postrema?
DR.
PETTY: This particular section, as you
point out, is through the striatum and one area of the cortex. We have examined other areas of the brain. The PET scans can be examined throughout the
entire area of the brain.
And
we find that aprepitant does displace the binding of the tracer and from the
receptor throughout all regions of the brain.
And we have demonstrated that this tracer does bind in the brain stem to
the areas in question.
CHAIRPERSON
CAMILLERI: A subsidiary question, I
think the brief shows that there are autoradiographic studies that are more
focused on dorsal motor nucleus of the vagus and nucleus of tractus solitarius.
So
can you tell us whether the other nuclei are like ambiguous in dorsal motor
nucleus, rather than the NTS, also have displacence of NK1? Because those would be perhaps more relevant
in the context of the retching and the vomiting.
And
a question for you, Dr. Petty. I saw the
occipital cortex of the cerebellum also lights up. So are there any toxicity studies looking at
cerebella or occipital visual cortical functions when you give the NK1
antagonist?
DR.
HARGREAVES: Sir, I'm Rich Hargreaves
from pharmacology at Merck.
The
answer to your question is the PET resolution when we analyzed the data was for
the brain stem only. The resolution is
too poor to distinguish between those nuclei.
And so we have a parallel displacement looking over the general area of
the dorsal motor nucleus, but we can't distinguish specific neuronal groups.
CHAIRPERSON
CAMILLERI: But, to help the questioner,
you do have data in your profile, I believe, because I read it in the brief,
that there are autoradiographic studies in other animals that show binding to
dorsal motor nucleus of vagas or dorsal vagal complex which would be relevant
in its antiemetic effects.
DR.
HARGREAVES: Absolutely. I mean, the NK1 receptor is
present throughout those nuclei. And
there is a parallel displacement in certainly the preclinical species, such as
the ferret.
CHAIRPERSON
CAMILLERI: Thank you.
Question
about the occipital cortex or whatever is lighting up in the back of the brain?
DR.
PETTY: Yes. As shown on the PET scans, the tracer binds
to NK1 receptors within their known distribution, which would
include many cortical areas. Actually,
they are a very low concentration of receptors in the cerebellum. And the tracer actually reflects that as
well, although it is not displayed on that particular slide.
We
have not observed, particularly in our clinical studies, again, at doses much
higher and given for much longer duration of time, any adverse experiences that
would be related to potential effects on vision.
CHAIRPERSON
CAMILLERI: Ms. Cohen? Thank you.
MS.
COHEN: As you know, I'm the consumer
member. So you have to bear with me
while I ask you some questions.
First
of all, I noticed that in your clinical trials, you did four children. What percentage of the members in your trial
were special populations? I guess I am
part of the special population.
And
I have a few more questions. Would you
like me to give them all at once? Do you
mind?
CHAIRPERSON
CAMILLERI: If they are not on clinical
pharmacology, can I suggest that we pick them up later?
MS.
COHEN: Well, I do have a curious
question. On chemotherapy, on the drugs
that are used in chemotherapy, how many drugs did you test your aprepitant
against?
Also,
is there a common denominator within all of the chemotherapy drugs that do
induce the nausea and the vomiting?
CHAIRPERSON
CAMILLERI: Thank you.
DR.
HORGAN: I will answer your second
question first. We used cisplatin
because it is the prototypic drug for evaluating a novel antiemetic. The precise mechanism of how cisplatin and
other chemotherapeutic agents invoke nausea and vomiting is not completely
understood.
As
Dr. Petty mentioned, cisplatin and some of the other therapeutic agents have
been shown to invoke the release of serotonin from the enterochromaffin cells
in the gut. And clearly they are likely
to elicit the release of Substance P acting at the NK1 receptor in
the brain stem.
Apart
from those two mechanisms, it is not really understood what the precise
mechanisms are that are responsible for evoking the symptoms.
Does
that answer your question?
MS.
COHEN: If I'm allowed to say something
more? To a certain extent. And that in itself is a puzzle to me in terms
of how this all works, obviously.
I
am also interested in how you dealt with the patients who were getting
chemotherapy in the normal controls and how you can simulate the kinds of
things that would happen.
DR.
HORGAN: Well, the assessment of efficacy
was done in patients receiving cancer chemotherapy. So all of our assessments of efficacy were
done in that patient population. So we
were doing clinical trials in the context of clinical practice.
MS.
COHEN: And the special population, what
percentage of that?
DR.
HORGAN: In fact, we actually enrolled in
the Phase III program a total of six adolescents. The data are mentioned in the background for
four. Those were I think the only
patients that you would describe as being special that didn't conform to the
general enrollment criteria of the general trials.
MS.
HOGAN: Well, in the aging population,
like me, how many of those did you have?
DR.
HORGAN: Well, that was included in our
general population.
MS.
HOGAN: Yes, but ‑‑
DR.
HORGAN: And that was ‑‑
MS.
HOGAN: Thank you.
DR.
HORGAN: ‑‑ more than 30 percent
of the patients.
MS.
HOGAN: At what age? Do you have any idea?
DR.
HORGAN: It would be 65. Approximately 30 percent were more than 65.
MS.
HOGAN: Thank you very much.
CHAIRPERSON
CAMILLERI: Dr. McLeod?
DR.
McLEOD: A clinical pharmacology question
for Dr. Petty. It's two different
questions, each with eight parts.
(Laughter.)
DR.
McLEOD: No. There are two specific questions that are
interrelated. And they really go around
the area of variability.
First
of all, if you could maybe walk us through your selection of a fixed dose
versus milligrams per meter2 or other individualized dosing
approaches and also talk a little bit about the linearity of the
pharmacokinetics of this agent across the different doses that were utilized,
recognizing that the starting dose for patients may change as there is further experience
gained with this agent.
DR.
PETTY: If I can address your second
question first? I believe your first
question is related to the dose of chemotherapies, if I'm not mistaken. Sorry.
DR.
McLEOD: No. All about the dose of this agent.
DR.
PETTY: Of aprepitant?
DR.
McLEOD: Yes.
DR.
PETTY: I see. In that case, the doses of aprepitant used at
125‑milligram, 80‑milligram are the only doses that we are
proposing for this particular indication.
They are not adjusted per meter2.
We
have demonstrated that for these two doses, there is slight nonlinearity in the
pharmacokinetics of the drug in that there are slightly higher plasma
concentrations as the dose is increased.
We
did study other doses as well. And we
determined with this particular regimen with the dose of 120 milligrams on day
one and 80 milligrams on subsequent days that it provides a relatively
consistent plasma concentration across the time interval that we're looking.
We
did study the kinetics in elderly patients with renal insufficiency, hepatic
insufficiency, found relatively minor effects that would not necessitate dose
adjustment of aprepitant. So we would
not recommend dose adjustment for other situations.
DR.
McLEOD: When you look across the more
extensive doses that you used during your Phase II and Phase I programs, when
you talk about nonlinearity, how dramatic is this nonlinearity as you expand
the dosing?
DR.
PETTY: Well, for these two doses
specifically, which are the only two doses we're proposing for clinical use, if
I can refer to one of my slides here ‑‑ I'm sorry. It will take just a minute. We're getting there. Just a second. If we could have slide 1324, please?
CHAIRPERSON
CAMILLERI: I'm wondering whether this
might be a good time to have a very brief break, let you find the information
you want, and then come back to the same questions from Dr. McLeod. And then Dr. Cryer will resume questions as
well.
Let's
take a five to ten‑minute break.
And we will be back at 10:50.
(Whereupon, the foregoing matter
went off the record at 10:41 a.m. and went back on the record at 10:53 a.m.)
CHAIRPERSON
CAMILLERI: I would like to bring the
meeting back to order.
Thank
you, Dr. Petty. You are back at the
podium.
Dr.
McLeod, would you like to remind us of the two questions? And then Dr. Petty will respond.
DR.
McLEOD: The questions really are posed
around trying to understand the degree of variability in pharmacokinetics
across the doses that have been evaluated, including the doses which you have
put forward for the indication. So
understanding the linearity across those doses and then within that will help
answer the question of a fixed dosing versus dosing individualized to something
like body weight or body surface area.
DR.
PETTY: Sure. If I can have slide 1332, please? This was a study actually designed to assess
the dose proportionality of aprepitant.
In this case, it was given as a colloidal dispersion.
What
was done was in healthy subjects, doses as low as 10 milligrams up to as high
as 600 milligrams, which spans the dose range that we are proposing ‑‑
as you can see, this was the AUC in those subjects.
And
it was fairly linear throughout the entire range here. So, at least with respect to the area under
the curve and the drug, it is fairly linear over this particular dose range.
DR.
McLEOD: So the nonlinearity referred to
earlier, was that looking at intra‑patient differences in
pharmacokinetics when they got the loading dose versus the subsequent doses or
is it just a population mean at the ‑‑
DR.
PETTY: No. That was only comparing two doses in a
healthy population, a pharmacokinetic study.
CHAIRPERSON
CAMILLERI: Dr. Cryer?
DR.
CRYER: I just wanted to briefly come
back to this issue of pharmacokinetics with the combined antiemetic
regimen. So from your clinical trial
experience of patients who received the combined antiemetic regimen, there are
no pharmacokinetic evaluations of the chemotherapy regimen. Was that correct?
DR.
PETTY: Correct. In cancer patients, in the Phase III studies,
pharmacokinetic data were not collected, although the safety profile of
patients who were receiving the standard regimen both on ondansetron and dexamethasone
compared to the aprepitant regimen, in which all three agents were given
indicates that the safety profile was similar between the two groups. And we would conclude that there probably
were not significant pharmacokinetic interactions on that basis.
CHAIRPERSON
CAMILLERI: Dr. Kelsen?
DR.
KELSEN: Can we ask a nonclinical
pharmacology question yet?
CHAIRPERSON
CAMILLERI: Are we done with clinical
pharmacology? Dr. Houn?
DR.
HOUN: Hi. Florence Houn.
I
am just interested in Dr. Malcolm Rowland's opinion on slide 44 and his
interpretation of what he thinks is happening.
DR.
PETTY: Can we have slide 44, please?
DR.
ROWLAND: Yes. This is obviously a study and it was
indicated an ongoing study of looking at whether or not the target aprepitant
affected docetaxel. These are obviously
gained as you go along in the clinical study.
They're not easy to do, and you couldn't do these in normal volunteers.
What
this basically is saying is that there is virtually no effect of the aprepitant
on the docetaxel kinetics in this regimen.
This is a clinical dosage of the drug.
So
the right‑hand side is basically to look at the issue which does come up,
and that is variability. You can get
people high or low. And what you are
seeing is that looking at any one with respect to themselves as individuals,
there are no real changes that you can observe.
DR.
HOUN: Is this expected?
DR.
ROWLAND: Yes. The issue was a lot of the chemotherapeutic
agents are given intravenously. And I
think the data, the body of data, coming out is that aprepitant doesn't have a
strong effect on inhibition systemically.
Its main effect appears to be at the inner wall level. I think that is what we are seeing with the
data in general.
CHAIRPERSON
CAMILLERI: Dr. Levine?
DR.
LEVINE: Just had a question about the
rescue medications, whether it was a variety of benzothiazides, whether it was
up to the discretion of the individual investigators, or if they all were
limited to one, compazine or something else.
DR.
HORGAN: The choice of a rescue
medication was entirely left to the discretion of the investigator. We did provide a list of recommended
medications, but the specific agent chosen was based entirely at the discretion
of the investigator.
And
a wide variety were used. More than 40
percent of the patients who received rescue received metoclopramide, and then
the other specific agents were all used in less than 10 percent of patients. There was a wide variety.
What
we were really meticulous about was the instructions about when patients could
take rescue. And that's where we really
focused the precision of our instructions.
CHAIRPERSON
CAMILLERI: I think we should ask Dr.
Horgan to stay there now because we are going to open the questions for
clinical efficacy. Dr. Kelsen, you had
the first question.
DR.
KELSEN: So this touches a little bit on
the point of oral and intravenous drugs.
You have indicated that this agent has effects on some drugs and not on
others in the clinical pharmacology. And
we talked a lot about toxicity. And it
looks like it doesn't affect chemotherapy toxicity that much.
Do
you have data on chemotherapy effectiveness?
About 40 percent of your patients had lung cancer. I assume a number of those regimens were the
lung cancer regimens. Do you have data
on outcome to indicate that it doesn't affect therapeutic efficacy of the
treatment of the disease?
DR.
HORGAN: We did not formally assess the
efficacy of chemotherapy in these clinical trials. We followed the paradigm of the 5‑HT3
receptor antagonists.
As
you mentioned, many of the patients had lung cancer, but they also had a wide
spectrum of cancers. It's not possible
in the context of a trial like this to formally assess the efficacy of
chemotherapy.
In
general, the toxicities that we saw that would be predictably associated with
chemotherapy were well‑balanced between the treatment groups, indicating
that there was unlikely to be any pharmacokinetic explanation as to why the
efficacy of chemotherapy should be altered.
DR.
KELSEN: There are about 200 patients in
each group who had lung cancer, right?
We don't have data on response rate or survival or anything?
DR.
HORGAN: No. It wasn't possible given the heterogeneity of
the patient populations, their specific diagnoses, their specific
regimens. That has been the practice in
these trials. It's not, as you know, to
actually formally evaluate the efficacy.
DR.
KELSEN: I guess my interest was the
concern that there is an interaction with some pharmacokinetic interactions,
but you have answered my question. Thank
you.
MS.
HOFFMAN: In terms of the pediatric
population and clinical efficacy, one thing that I would like to say, I guess,
is that you mentioned that you didn't do a study arm without the use of
steroids.
From
the pediatric population, the impact of steroids can sometimes be as difficult
to deal with as the nausea and vomiting from a parent perspective, the mood
swings, the moon face, that sort of thing.
So a study arm spanning the pediatric population without the use of
steroids might be something to look at and to see the effectiveness of your
study drug without steroids.
CHAIRPERSON
CAMILLERI: Thank you for the comments.
Dr.
Proschan?
DR.
PROSCHAN: Yes. I was wondering. You measured nausea on a visual analog scale,
but you presented results in terms of nausea less than five yes or no. I am wondering whether you did any kind of
analysis of it in a continuous way.
DR.
HORGAN: Yes. We have looked at nausea very comprehensively. And the bottom line is that, whatever way we
look at it, we consistently see an advantage for the aprepitant regimen.
And,
actually, if I could have slide 203? The
reason we used the visual analog scale was because of its greater
sensitivity. And if I can just walk you
through this slide, which shows the data for both protocols combined? And it shows the distribution of maximum
visual analog scale ratings over each of the five days, the maximum reading
over each of the five days in which patients gave recordings.
So
on the horizontal axis, you see the peak nausea score. And then on the vertical axis, you see the
percentage of patients. So, for example,
if you look at a peak nausea rating of 40 and you look at the vertical there,
what you are seeing is this represents the percentage of patients who have a
peak nausea score of 40 or less. And you
can see that there are more patients in the aprepitant group who have a peak
score of 40 or less.
Now,
where we drew our lines for our two pre‑specified endpoints were at 5 and
at 25. You see at those cutoffs, we had
an advantage in the aprepitant group.
Now,
we could have drawn those vertical lines right across the spectrum of peak
nausea scores. And we would ultimately
have gotten the same outcome.
We
pre‑specified those for the reasons that I gave because there were prior
precedents. And they correlated with
impact on daily life. And this
difference for the analysis of the continuous data was statistically
significant.
CHAIRPERSON
CAMILLERI: Dr. Metz?
DR.
METZ: Thank you.
I
was thinking about what Dr. Kelsen was saying.
I don't know if it has been fully addressed. Excuse the naivete of all of this, but I
don't know anything about NK1 receptors. Does anyone know where in the body NK1
receptors are distributed? Especially
are there any NK1 receptors on any kind of tumor types at all? Has anyone looked?
DR.
HORGAN: There is some data that NK1
receptors are expressed by tumor cell lines, gliomas, some breast cancer lines,
and some small cell line cancer lines.
The
significance of those is not definitively known. There is some suggestion that blockade of
those receptors may alter the growth characteristics, reduce the growth of
those tumor cell lines. And that is
basically the extent of the current knowledge with regard to that.
CHAIRPERSON
CAMILLERI: Dr. LaMont?
DR.
LaMONT: Yes. I have a question relating to emesis and
nausea on slides 107 and 108. I am just
trying to reconcile the data given in slide 107, which says that at week 6,
approximately 75 or 80 percent of the aprepitant patients had no nausea;
whereas, if we look in the left panel of slide 108, it looks like the
percentage of patients with emesis is less than that.
I
just don't understand. I am trying to
reconcile these two slides and to understand the apparent decline in
efficacy. So it's a two‑part
question.
DR.
HORGAN: Okay. Well, the background to this is this is the
assessment of efficacy during multiple cycles of chemotherapy. And there is a variety of ways to look at
this data to provide insight into the efficacy profile.
The
first one that we showed in 107 is the observed proportion of patients without
emesis and without significant nausea.
The information derived from the two questions that patients were asked
at each chemotherapy cycle.
What
we are illustrating here is a snapshot at each cycle of what the outcome was
for those two variables. And it's not
linked, the outcome in each cycle is not linked, to what happened in the
preceding cycle. It's a snapshot at each
cycle. This is the efficacy profile that
we see.
I
don't think that you can really make an inference so much as to what is
happening, the trend over the cycles, within each treatment group. I think the key message here is the relative
difference between the treatment groups at each individual cycle.
Then
in the next slide, 108, this is a Kaplan‑Meier approach. In this case, for the time to first emesis, a
patient having emesis in the first cycle is obviously lost, then, in the
analysis for subsequent cycles. So it's
a different way of looking at the data.
And the outcome at each cycle reflects what is the outcome in previous
cycles.
Again,
the key message here is not so much the trend within each treatment group. It is the relative efficacy, the advantage
afforded by aprepitant during each cycle.
It is simply a different way of looking at the data.
CHAIRPERSON
CAMILLERI: Dr. Brawley?
DR.
BRAWLEY: Do you have any data about dose
reduction chemotherapy cycle to cycle?
DR.
HORGAN: Could you clarify?
DR.
BRAWLEY: I am wondering if patients were
given less chemotherapy in cycle 2 and cycle 3 versus cycle 1 or perhaps
because of less nausea, maybe even the patients were able to get full doses of
cisplatin in cycle 2 through ‑‑
DR.
HORGAN: Right. We didn't actually look at the dose that was
administered in subsequent cycles of chemotherapy. We didn't specifically address that question.
CHAIRPERSON
CAMILLERI: Dr. Proschan, I will follow
you.
DR.
PROSCHAN: Okay. Thank you.
You
know, in some of your slides, like the last one you show, you have got both of
those protocols, 052 and 054, combined.
And in others, you look at them separately. I don't mean to be cynical, but I am guessing
that the combined ones are when you didn't have significance of either one
separately.
DR.
HORGAN: Well, the displays are really
done for combined for reasons of convenience.
We did not do statistical testing on the data for the multiple cycle. So these are displays of efficacy.
And
the bottom line is that a similar picture was seen in the individual displays.
CHAIRPERSON
CAMILLERI: Dr. Horgan, I have a question
pertaining to whether the 40/25 regimen is really less effective. I would like to refer you to your charts 82
and 83 because there is something there that I don't completely understand.
DR.
HORGAN: Here you see the 40/25 regimen
has an overall complete response rate of 59 percent. In 83, next slide, please. Somehow when you look at the information
separately for acute and delayed, it goes up from 59 to 76 and 64. And here there doesn't seem to be a
significant difference.
So
my question to you is, is it true that the minimum effective dose perhaps or
the maximum dose here is the 125/80 relative to the 40/25?
DR.
HORGAN: Right. Well, the first part of your question, the
apparent discrepancy, there isn't a precise correlation between efficacy in the
acute phase and the delayed phase. There
is a correlation, but it's not precise.
So
some patients here who had controls during the acute phase of the 76 percent of
patients would have gone on to have symptoms in the delayed phase and vice
versa, which is why when you merge the two phases below, that the overall
response that you're seeing, the 59 percent you mentioned, is actually lower
than what you see in the delayed phase alone because the correlation is not
precise.
And
if you go back to slide 82? So what we
saw in the data that we gathered in this study for the spectrum of endpoints
that we used, there was consistently always a numerical advantage for the
125/80 milligram regimen versus the control regimen.
And
then when we did a formal analysis for the primary endpoint of overall complete
response, we saw a statistically significant difference here, justifying our
selection of the 125/80 dose.
CHAIRPERSON
CAMILLERI: Ms. Cohen?
MS.
COHEN: I want to make sure I understood
Dr. Kelsen's question and your answer to him in terms of the effectiveness
against medication or an anti‑chemotherapy. You didn't study if there was any
relationship to the efficacy of the drug itself affected by aprepitant?
DR.
HORGAN: We did not formally assess
whether aprepitant altered the efficacy of chemotherapy.
MS.
COHEN: Well, then would it not be
appropriate to tell a patient that "We can reduce your nausea and
vomiting, but we don't know the effect of the chemotherapy, how it affects the
chemotherapy"? I would want to know
that. I think I am entitled to know
that. Wouldn't you think so as a
patient?
DR.
HORGAN: Well, the data we have on the
drug strongly suggest that there is no interference with the pharmacokinetics
of the chemotherapy that the patient is administered; in other words, the
levels of the chemotherapy.
MS.
COHEN: Well, was that specifically
studied?
DR.
HORGAN: Yes.
MS.
COHEN: Go ahead. And I have one other question, then. I didn't know if there were other
chemotherapy drugs that you didn't test with aprepitant. That would be my second question.
DR.
REINES: Sorry. If I could comment on your question because
it is so critical? If we could have
slide 133? Although it is not possible
in studies of this size and duration to formally assess the efficacy of the
chemotherapy regimen on the cancer, as a surrogate of that, we look carefully
at the toxicity due to the chemotherapy because the efficacy would be expected
to be related to how much toxicity the chemotherapy is causing. This essentially is a measure of the exposure
the patient gets to the chemotherapy at the level of the bone marrow.
As
you can see, I emphasized in my presentation that there wasn't more neutropenia
in the aprepitant group, but there is not less neutropenia either, which means
that there should not be any less exposure in those patients.
And
so, as a surrogate of efficacy since we couldn't measure pure efficacy of the
chemotherapy regimen, we looked very carefully at parameters like this. And we didn't find any evidence that there
might be a reduction in the exposure to the chemotherapy agent.
CHAIRPERSON
CAMILLERI: Dr. LaMont and then Dr.
McLeod.
DR.
LaMONT: Yes. You list a death rate of 6.8 percent in the
aprepitant group out of 413 patients versus 5.3 in the controls. I wonder if any of those deaths are
attributable, in part or in total, to aprepitant.
DR.
REINES: During the first cycle of
chemotherapy, the death rate was 20 in the aprepitant group and 21 in the
control regimen. So it was very evenly
balanced. Over multiple cycles, we
observed the death rates that you described.
If
we could go to slide 515, please?
Sorry. If we go to 516 first,
this shows the death rate by cycle beyond cycle 1. And, as you can see, there is no pattern
there of an increase, although it does lead up to this small differential that
you mentioned.
If
we go to 517, this displays over the multiple‑cycle data the percentages
6.8 and 5.3 and the primary causes. None
of these were attributed to aprepitant.
And they were virtually all attributed to the underlying disease in the
patients.
CHAIRPERSON
CAMILLERI: Dr. McLeod?
DR.
McLEOD: My question is actually more
probably for Dr. Horgan. There are three
main components to chemotherapy‑induced nausea and vomiting. The acute and the delayed phase you have
presented the information on. I wondered
if you had any data on the degree of anticipatory nausea and vomiting that
occurred during cycles 2 and beyond as a way of understanding the level of
control that the two arms evaluated had during the first cycle of chemotherapy.
DR.
HORGAN: Right. Unfortunately, we didn't formally assess that
because, as I mentioned, our approach to the collection of efficacy data during
multiple cycles was streamlined and simply reflected the two questions that
patients were asked at the day six to eight clinical visit. So we didn't formally assess the incidence of
anticipatory symptoms.
CHAIRPERSON
CAMILLERI: Thank you.
I
believe we have had enough questions on the presentation from the
sponsors. I would like to invite the FDA
presentation. The first presentation is
on the clinical summary by Dr. Gary Della'Zanna. He will be followed by pharmacology by Dr.
Jarugula.
FDA
PRESENTATION
CLINICAL
SUMMARY
DR.
DELLA'ZANNA: Good morning. My name is Gary Della'Zanna. I'm a medical officer in the Division of
Gastrointestinal and Coagulation Drug Products at the Food and Drug
Administration.
I
would like to take the time to introduce the other divisions involved in this
presentation. Dr. Wen‑Jen Chen is
a mathematical statistician from the Division of Biometrics II. And Dr. Venkat Jarugula is a clinical
pharmacology reviewer from the Office of Clinical Pharmacology and
Biopharmaceutics.
During
today's presentation, I will give a brief background of aprepitant, touching on
a treatment regimen and the proposed indication. Efficacy results will be presented for the
**primary endpoint and some of the secondary endpoints that are relative to the
proposed indication.
I
will present the questions the agency has in regard to the dose of highly
emetogenic cisplatin and our safety concerns for potential drug‑drug
interactions. Following my presentation,
Dr. Jarugula will explain the metabolism of aprepitant in detail and the
potential for drug‑drug interactions.
On
September 27, 2002, Merck and Company submitted a new drug application for
aprepitant. Aprepitant is a New
molecular entity that, if approved, would be the first in a new therapeutic
class, the NK1 receptor antagonist.
At the time of the submission, the applicant requested and was granted
priority review status.
The
proposed treatment regimen is a three‑drug therapy that includes
aprepitant in combination with a 5‑HT3 antagonist and a
corticosteroid. The applicant has
requested an indication for the prevention of acute and delayed nausea and
vomiting associated with initial and repeated courses of highly emetogenic
chemotherapy. Aprepitant would be the
first drug to be granted an indication that includes the delayed phase of
chemotherapy‑induced nausea and vomiting.
One
of the questions the agency has is in regard to the primary endpoint and
whether the submitted data supports the proposed indication. The primary endpoint for both Phase III
studies was defined as complete response in the overall phase. A patient was considered to have complete
response if they did not vomit and did not require rescue therapy. The overall phase was from zero hours to 120
hours after the administration of cisplatin.
The
complete response endpoint was evaluated and analyzed for three distinct time
periods, the overall phase being the primary endpoint with the acute and
delayed phases being secondary endpoints.
Since
the proposed indication is for nausea and vomiting in the acute and delayed
phases, each were analyzed independently as secondary endpoints.
The
agency reviewed the applicant's data and concurs with the results of the major
analysis. The sponsor successfully
demonstrated the aprepitant regimen was superior to standard therapy for the
primary endpoint, complete response in the overall phase, as well as the
secondary endpoints of complete response in the acute and delayed phases and
the no vomiting endpoints in the overall, acute, and delayed phases.
Next
slide. Results of the no nausea
endpoints, however, were not as persuasive.
This table displays the results of the no nausea endpoints for the two
Phase III studies.
The
nausea endpoints were evaluated for three time periods using two separate
criteria that were based on a 100‑millimeter visual analog scale. The no nausea endpoint was defined as a VAS
rating of less than five millimeters with no significant nausea being less than
25 millimeters.
I
would like to draw your attention to the top portion of this chart for the no
nausea endpoint. The no nausea endpoints
were only statistically significant in the overall and delayed phases of study
054. The aprepitant regimen did not
reach statistical significance in the acute phase of study 054 or any of the
three phases in study 052.
Additionally,
the no significant nausea endpoint, shown here on the lower half of this table,
was only statistically significant in the acute phase of study 054 with an
unadjusted p value of 0.01. Because several predefined secondary and
exploratory endpoints were analyzed, the nominally significant results cannot
be taken at face value due to multiple comparisons.
The
agency agrees with the firm that the results of the nausea endpoints may have
been affected by the use of rescue therapy.
Twenty‑eight percent of the patients in the standard therapy group
required rescue therapy compared to 18 percent in the aprepitant group.
Furthermore,
time to analysis showed that the time interval for the use of rescue therapy
was longer in patients in the aprepitant group than the standard therapy group.
However,
since this would be the first time that the agency granted an indication for
chemotherapy‑induced nausea and vomiting in a delayed phase and the
results of the nausea endpoints independently were not statistically
significant, the agency would like the committee's opinion on whether the data
supports the applicant's proposed indication.
The
agency would also like comment from the committee regarding the dose of
cisplatin considered highly emetogenic.
This dose varies in the medical literature**. In the clinical trials that led to the
approval of ondansetron, a highly emetogenic dose of cisplatin was greater than
100 milligrams per meter2.
The present ondansetron label describes the range of 50 to 80 milligrams
per meter2 as a moderate emetogenic dose.
The
aprepitant Phase III protocol clearly defined a highly emetogenic dose of
cisplatin as greater than or equal to 70 milligrams per meter2. In spite of this, approximately 20 percent of
the patients in these studies received less and were still included in the
efficacy analysis.
As
part of the submission, the firm included recent literature that defines a
highly emetogenic dose of cisplatin as greater than 50 milligrams per meter2.
The
agency performed additional analysis excluding patients who received less than
70 milligrams per meter2. And
the efficacy was maintained for the primary endpoint of complete response in
the overall phase as well as the secondary endpoints of complete response in
the acute and delayed phases.
The
agency's question for the committee is whether any or all of the patients in
the Phase III trials received a highly emetogenic dose of cisplatin.
Additional
concerns the agency has are related to potential drug‑drug interactions
that have not been thoroughly evaluated.
Aprepitant has a complex metabolic pathway. It has been identified as a substrate, a
moderate inhibitor, as well as an inducer of CYP3A4. In addition to this, aprepitant is also an
inducer of 2C9.
The
proposed treatment regimen states aprepitant may be used in combination with
any 5‑HT3 antagonist and a corticosteroid. The applicant has exposure and
pharmacokinetic data for only ondansetron and granisetron.
In
these drug interaction studies, aprepitant did not have clinically important
effects on the pharmacokinetics of the specific drugs in the formulations
studied. The agency does not have any
data for the intravenous formulation of granisetron or the oral formulation of
ondansetron.
Because
of first pass metabolism, the inhibitory effect is greatest in the oral
formulation. Therefore, one cannot
extrapolate PK results from the intravenous ondansetron studies to its oral
formulations.
One
needs to consider that oral antiemetics may be utilized as rescue therapy. This could result in higher plasma
concentrations of these drugs.
Additionally,
within the class of 5‑HT3 antagonists, there are differences
in metabolic pathways. Both ondansetron
and granisetron are predominantly metabolized by CYP3A4. Dolasetron, however, is metabolized by carbonyl
reductase to hydrodolasetron. Further
metabolism is then through CYP2D6, 3A4, and flavin monooxygenase.
The
agency presently has no data on the use of the aprepitant regimen with
dolasetron. This is a concern since it
is the only 5‑HT3 antagonist that has QTc and cardiac warnings
in its label.
Since
dolasetron utilizes different metabolic pathways than ondansetron and
granisetron and there are no exposure data on the use of the aprepitant regimen
with dolasetron, the agency seeks advice as to whether the regimen proposed in
the label should specify only the 5‑HT3 antagonists that have
been studied. Additionally, the agency
would like the committee's opinion on whether any additional studies are
recommended for dolasetron and/or the oral formulation of ondansetron.
During
the Phase III trials, approximately 95 percent of the patients received a
concomitant chemotherapeutic agent in addition to the protocol cisplatin. The agency questions whether enough safety
data exists to use aprepitant with all chemotherapeutic agents at highly
emetogenic doses.
Presently
there are no completed PK data available regarding drug‑drug interactions
of the aprepitant regimen with other chemotherapeutic agents.
The
applicant does have an ongoing drug interaction study with docetaxel, which is
primarily metabolized through 3A4 pathways.
The available data for the five patients enrolled has been reviewed by
the agency. The data suggest that the
aprepitant regimen has no effect on plasma concentrations of docetaxel.
Aprepitant
is a moderate inhibitor of 3A4. The
agency would have anticipated some effect on the metabolism of docetaxel
considering the effect the aprepitant regimen had on other drugs evaluated.
The
agency questions whether docetaxel is a sensitive enough probe and has concerns
as to whether the results of the pending docetaxel study can be used to make
generalizations about the safety of the aprepitant regimen with all oncologic
agents metabolized through 3A4 pathways.
One
well‑documented drug‑drug interaction was identified during the
development of aprepitant. During the
Phase IIb trials, an interaction with dexamethasone was identified. This ultimately **led to the sponsor
redefining the aprepitant regimen for the Phase III trials and resulted in a
decrease in the dexamethasone dose by 50 percent in the aprepitant group.
Similar
drug‑drug interaction studies have not been completed with
chemotherapeutic agents metabolized through 3A4 pathways. This will be discussed in further detail
during the biopharmaceutical presentation.
During
the Phase III trials, in addition to the protocol cisplatin, 517 patients were
treated with a concomitant chemotherapy metabolized through 3A4 pathways. In spite of the number of patients, there is
only limited safety data on most 3A4‑metabolized agents.
Common
agents known to be 3A4 substrates are listed here along with the number of
patients that received them. Of these,
the applicant has no safety data for irinotecan or imatinib and has only very
limited information on several others.
Although specific PK data is not available for any of these, there is
reasonable exposure data for paclitaxel, vinorelbine, and etoposide.
Overall,
the incidence of adverse events was similar between treatment groups in
patients receiving 3A4‑metabolized chemotherapy. However, when analysis was performed of
serious adverse events by body system, a higher incidence of hematologic and
infection‑related adverse events was seen in the aprepitant group during
cycle 1.
In
the aprepitant group, septic shock was reported in three patients, sepsis in
one patient, and a serious upper respiratory infection in one patient. In the corresponding standard therapy group,
there were no reports of these serious adverse events.
Neutropenia
was reported as a serious adverse event in eight patients receiving the
aprepitant regimen compared to only two patients in the standard therapy
group. The incidence of anemia and
thrombocytopenia were similar between treatment groups.
It
is worth noting that during the multi‑cycle extension, the incidence of
hematologic serious adverse events appear to be similar between the treatment
groups. The applicant did perform
additional safety analysis broken down by concomitant chemotherapy for the most
common agents used during the Phase III trials.
In
order to focus on the primary concerns, the remainder of this presentation will
address serious adverse events in patients who received concomitant
chemotherapy metabolized through 3A4 pathways.
Going
in order by number of patients exposed, the first agent we will discuss is
etoposide, which is a 3A4 substrate.
During the Phase III trials, 197 patients received etoposide in
combination with cisplatin. This breaks
down to 106 patients in the aprepitant group and 91 patients in the standard
therapy group.
Overall,
the incidence of serious adverse events in this population was similar between
treatment groups, occurring in approximately 15 percent of the patients.
By
analyzing the distribution of these adverse events by body system, it was noted
that three times as many serious hematologic adverse events occurred in the
aprepitant group.
Neutropenia,
thrombocytopenia, and anemia were reported as serious adverse events only in
the aprepitant group. When you include
both serious and non‑serious infection‑related adverse events,
there were more than twice as many patients reporting an infection in the
aprepitant group. Eighteen percent of
the patients in the aprepitant group developed an infection compared to nine percent
in the standard therapy group.
Furthermore, only patients in the aprepitant group reported serious
infection‑related adverse events.
The
agency is concerned over this trend.
However, the numbers of patients are too small to establish any
conclusions.
The
next most common 3A4‑metabolized agent was vinorelbine. A total of 158 patients were treated with
this in combination with cisplatin. The
incidence of serious adverse events was higher in the aprepitant group than the
standard therapy group.
Overall,
the incidence of serious hematologic adverse events was similar in both
treatment groups. However, serious
infection‑related adverse events were higher in the aprepitant
group. Four patients in the aprepitant
group were described as having a serious infection compared to two in the
standard therapy group. There were three
reported cases of sepsis or septic shock as serious adverse events, and all
occurred in the aprepitant group.
On
further analysis, there was a marked difference in the incidence of serious
respiratory‑related adverse events.
Six of the 82 patients in the aprepitant group compared to only one of
the 76 patients receiving standard therapy experienced a respiratory‑related
serious adverse event.
There
were no patients in the standard therapy group who experienced respiratory
insufficiency; whereas, four patients receiving the aprepitant regimen
developed a fatal respiratory insufficiency.
In addition to these four fatalities, *three deaths occurred in this
subpopulation of the aprepitant group.
Two patients died from septic shock and one from cardiopulmonary arrest.
In
the corresponding standard therapy group, there were only two fatalities
reported. One patient died as a result
of a pulmonary emboli. And the other
patient's cause of death was reported as unknown.
Vinorelbine
is known to have pulmonary toxicity. The
agency has concerns that the aprepitant regimen may have affected this toxicity
since all fatal cases of respiratory insufficiency occurred in the aprepitant
group. The regimen may also increase the
risk of serious infections in patients receiving vinorelbine. However, the numbers are too small to draw
any definite conclusions.
The
next most common 3A4‑metabolized chemotherapeutic agent was
paclitaxel. A total of 110 patients were
treated with paclitaxel in combination with cisplatin. On analyzing the data, there was little
difference between treatment groups for hematologic or infection‑related
adverse events.
The
remaining chemotherapeutic agents characterized as 3A4 substrates either had no
or too few patients to permit meaningful analysis. This is a concern for the agency because of
potential drug‑drug interactions.
And the proposed label offers little guidance to the prescribing
physicians.
Under
the "Precautions" section of the label, the applicant states,
"EMEND should be used with caution in patients receiving concomitant
medicinal products that are primarily metabolized through CYP3A4. Some chemotherapy agents are metabolized by
CYP3A4."
The
agency would like the committee's opinion on whether the present safety data is
adequate and whether any additional drug‑drug interaction studies should
be performed since several of the chemotherapeutic agents had too few patients
to establish a safety profile.
To
better understand the agency's concerns, the Office of Biopharmaceutics will
present their findings now. And then we
will have questions.
DR.
JARUGULA: Thank you, Dr. Dalle'Zanna.
BIOPHARMACOLOGY
SUMMARY
DR.
JARUGULA: Good morning. I am Venkat Jarugula, clinical pharmacology
and biopharmaceutics reviewer of the nda.
Dr. Myong Jin Kim of my division has also been doing giant review with
me of this NDA.
This
morning the sponsor has already discussed the pharmacological properties of
aprepitant. So I am not going to repeat
this. For the next 20 minutes, I am
going to present on drug interactions of aprepitant.
My
presentation is divided into the following.
First I will give a brief introduction on the metabolism of
aprepitant. Then I will present the
results of key drug interaction studies that demonstrate aprepitant as a CYP3A4
inhibitor and then discuss the effect of other drugs on aprepitant followed by
drug interactions with 5‑HT3 antagonists. Then I will discuss the most important issue,
the potential of aprepitant to interact with chemotherapy agents that are
metabolized by CYP3A4, followed by my conclusions.
Aprepitant
is extensively metabolized in humans, primarily by oxidation by CYP3A4
isozyme. Based on the in vitro and in vivo studies, aprepitant regimen is shown to inhibit CYP3A4 as
early as one hour after drug administration on day one. Aprepitant regimen induces CYP2C9 isozyme.
Upon
multiple dose administration for more than two weeks, aprepitant induces its
own metabolism by autoinduction. This
phenomenon is not relevant for the current indication. However, this may be important for chronic
administration of aprepitant.
Next
slide. This slide shows the effect of
aprepitant on various CYP3A4 substrates.
The AUC ratio of the CYP3A4 substrate with and without concomitant
administration of aprepitant is given in this chart. For comparison, the AUC ratio of control is
given as one.
As
can be seen here, the aprepitant regimen significantly inhibited the metabolism
of midazolam, which is a sensitive CYP3A4 substrate. As can be seen here, the aprepitant regimen
significantly inhibited the metabolism of midazolam, a sensitive CYP3A4
substrate, resulting in a 3.34 increase in AUC on day five of aprepitant
regimen.
Dexamethasone,
as you see, also was increased by 2.24 of this interaction. Sponsor has reduced the dose of dexamethasone
in clinical studies by half the drug standard regimen for chemotherapy‑induced
nausea and vomiting.
The
diltiazem, as you see, also was increased by 1.74. Methylprednisolone, also a CYP3A4 substrate,
when administered after all administration with aprepitant, diltiazem is a
significantly higher AUC change of 2.54 compared to its IV administration of
1.344. This interaction suggests that
aprepitant as a CYP3A4 inhibitor has less effect on IV‑administered drugs
compared to the oral‑administered drugs.
Based
on these interactions, the sponsor has, in fact, recommended in the proposed
package insert that the IV dose of methylprednisolone be reduced by 25 percent
and the oral dose of methylprednisolone be reduced by 50 percent when co‑administered
with aprepitant.
Next
slide. This just shows the effect of
CYP3A4 inhibitors or inducers on aprepitant.
Again, the AUC ratio of aprepitant with or without concomitantly
administered CYP3A4 drug is shown here.
Ketoconazole,
an important CYP3A4 inhibitor, significantly increased AUC of aprepitant by
five‑fold while diltiazem, a moderate CYP3A4 inhibitor, resulted in an
increase of two‑fold change in the AUC of aprepitant.
Dexamethasone
resulted in a modest increase of 30 percent in AUC. On the other hand, rifampin, an important
CYP3A4 inducer, resulted in production of almost an 11‑fold change in AUC
of aprepitant.
It
should be noted that these drugs are not a part of aprepitant's regimen, and
the sponsor included a caution in the label when these drugs are to be co‑administered.
The
other significant drug interactions of aprepitant, aprepitant regimen reduces
the S‑warfarin. And the INR also
is reduced by aprepitant. Therefore, the
patients on warfarin need to be monitored carefully when aprepitant is co‑administered
with warfarin.
Upon
multiple dosing for two weeks, the aprepitant reduces the level of ethinyl
estradiol by 40 percent and reduces the efficacy of oral contraceptive. This interaction is relevant for the current
application of aprepitant. However,
since the aprepitant regimen for three days is not studied, sponsor has
appropriately recommended in the label to use a backup contraceptive method for
a woman.
Many
chemotherapy agents are substrates for P‑glycoprotein transporter. Aprepitant regimen does not significantly
affect the P‑glycoprotein transporter as there is no effect on the
pharmacokinetics of digoxin, which is a P‑gp substrate. Therefore, aprepitant regimen is not likely
to interact with chemotherapy agents via the P‑gb transporter mechanism.
The
drug interactions with 5‑HT3 antagonists, two pharmacokinetic
drug interactions were conducted. These
studies showed that aprepitant does not significantly affect the
pharmacokinetics of IV ondansetron and oral granisetron. However, there is no data on PK drug
interaction with oral ondansetron.
In
general, the pharmacokinetic interaction with oral administration of drugs is
greater than intravenous administration, mainly because of the inhibition of
the dose effect involved in oral administration. However, the package insert for ondansetron
states that "This drug is metabolized by multiple p450 isozymes. Therefore, significant drug interactions are
not likely."
Furthermore,
there is no PK drug interaction data with dolasetron. It is reported that dolasetron is metabolized
by multiple metabolic pathways with carbonyl reductase and CYP2D6 being the
main pathways. And CYP3A4 plays a minor
role.
Therefore,
the pharmacokinetic interaction with dolasetron is not likely. However, as Dr. Della'Zanna mentioned, there
is no clinical safety data on co‑administration of aprepitant with
dolasetron.
Coming
to the most important issue today, the potential of aprepitant to interact with
chemotherapy drugs metabolized by CYP3A4.
As mentioned previously, aprepitant is a moderate CYP3A4 inhibitor.
Many
chemotherapy drugs are known to be metabolized by CYP3A4. And, therefore, concomitant administration of
aprepitant may increase the systemic exposure to these chemotherapy agents and
may result in serious or life‑threatening toxicity.
Next
slide. The NDA does not consist of any
control drug‑drug interaction studies with these chemotherapy agents
except an ongoing study with IV docetaxel.
Although many chemotherapy agents are known to be metabolized by CYP3A4,
there is inadequate information in the literature regarding the role of CYP3A4
in the metabolism and regarding the drug‑drug interactions with CYP3A4
inhibitors.
There
are two studies reported in the literature with ketoconazole. One study reported that the ketoconazole
increases the exposure of SN‑38, the active metabolite of irinotecan, by
100 percent.
Another
study reported that ketoconazole does not significantly affect the
pharmacokinetics of paclitaxel as this drug is metabolized by multiple
pathways. This result is consistent with
the lack of safety signal noted by Dr. Della'Zanna in the safety database of
the NDA for patients who are on paclitaxel.
As
Dr. Della'Zanna also discussed, there is some safety data available in the NDA
for patients who are on etoposide, paclitaxel, and vinorelbine. However, there is minimal or no data
available on co‑administration of aprepitant with irinotecan, ifosfamide,
imatinib, vinblastine, and vincristine, which are also known to be CYP3A4
substrates.
As
mentioned previously, there is a drug interaction study ongoing with IV
docetaxel. The primary data on five
patients show no interaction with docetaxel.
Since
the docetaxel is known to be metabolized by CYP3A4, it is rather surprising to
see no effect of aprepitant on docetaxel.
Therefore, the interaction results of docetaxel may not be generalized
to other chemotherapy agents.
As
mentioned previously, the sponsor's proposed package insert in the
"Precautions" section states that "EMEND should be used with
caution in patients receiving concomitant medicinal products that are
metabolized through CYP3A4. Some
chemotherapy agents are metabolized by CYP3A4."
However,
the label does not list these chemotherapy agents, and the NDA does not contain
any information or data to provide dosage adjustment or appropriate caution
when aprepitant is co‑administered with these chemotherapy agents.
Conclusions. Aprepitant is extensively metabolized in
humans, primarily by a CYP3A4 isozyme.
Potent inhibitors increase the aprepitant exposure significantly. Potent inducers reduce the aprepitant
exposure significantly. And based on the
drug‑drug interaction studies, aprepitant is known to inhibit the CYP3A4
metabolism of the co‑administered drugs.
Co‑administration
of aprepitant with the chemotherapy agents that are metabolized by CYP3A4 may
increase the exposure to these agents and may result in serious or life‑threatening
toxicity.
Finally,
the potential of aprepitant to interact with the chemotherapy drugs that are
metabolized by CYP3A4 has not been characterized adequately.
This
concludes my presentation. Thank you
very much for your attention.
CHAIRPERSON
CAMILLERI: Thank you, Dr. Della'Zanna
and Dr. Jarugula. Maybe you should both
be at the microphone now to address questions from the committee members
pertaining to your presentations. Dr.
Kelsen?
QUESTIONS ON
PRESENTATIONS
DR.
KELSEN: Well, I thank you for that
review. I think the point we were
discussing a few minutes ago is that, is there a chance that the antiemetic
will affect outcome from the therapy?
I
think there are two sides to that. You
have discussed toxicity. I guess I would
just make the comment that, unfortunately, there is not a direct correlation
between therapeutic efficacy and toxicity with many chemotherapeutic
agents. That is, not all patients who
have serious toxicity also have an excellent response.
The
MTDs are developed because that is the maximum dose that you can give. But making assumptions that because you don't
see much more in the toxicity, you, therefore, will see equal efficacy**, that
may not be a direct correlation.
CHAIRPERSON
CAMILLERI: In fact, wasn't the analogy
that since there wasn't less toxicity, there should be similar therapeutic
efficacy?
DR.
KELSEN: Yes. I guess what I am trying to say is that I do
understand the hypothesis, but I think that's a hypothesis, hasn't been proven.
I
also am aware that it is not usual to look at therapeutic endpoints with
antiemetics, but the reason I asked that before is that many antiemetics don't
apparently have this degree of drug‑drug interaction. So I think it is a little bit of a different
situation.
CHAIRPERSON
CAMILLERI: Dr. LaMont?
DR.
LaMONT: Yes. I wonder if there was a clustering in the
same patients of infectious adverse events and neutropenia or can you tell if
these are separate or the same patients?
DR.
DELLA'ZANNA: I'm not sure from the data
that I have right now. I don't know if
the firm would have any input on that, if that was clustered together.
DR.
REINES: Seven eighty‑seven,
please. Okay. So this is the infections in the total
population in Phase III, cycle 1. And,
as you can see, most of the infections are not neutropenic infections, either
in the aprepitant or in the control regimen.
CHAIRPERSON
CAMILLERI: Dr. Levine?
DR.
LEVINE: Just to follow up that slide and
Dr. LaMont's question. It's of interest
in very large studies in hepatitis, interferon causes neutropenia, but it
doesn't seem to be causing a correlation with infection very often.
There
is a disconnect because if one looks at the individual white count and then go
down to neutrophils percentage and then go down to the absolute neutrophils,
there is a much better correlation.
So
I wondered perhaps later at a time ‑‑ you probably don't have that
data ‑‑ whether the absolute neutrophil count, the percent in the
absolute neutrophil count, was, in fact, a disconnect, as opposed to the data
you showed. But it is interesting that
that large data didn't seem to show a very good correlation either.
DR.
DELLA'ZANNA: Well, one of the concerns
the agency has wasn't necessarily related specifically to the incidence of
serious adverse events as much as the incidence of serious adverse events for
specific chemotherapeutic agents.
We
realize that the numbers that we were talking about were small and the
differences were small. But when you
broke them down specifically ‑‑ for example, can you go to slide
16?
Etoposide. Overall, the incidence of serious adverse
events was identical, but when you looked at them specifically for neutropenia,
there were three times as many. The
results that the firm has presented have been serious adverse events overall
inclusive of both CYP3A4 and non‑CYP3A4 or CYP3A4s completely inclusive.
Now,
like paclitaxel, we saw no difference at all in either hematologic or infection‑related
adverse events. So I don't think we can
look at them as a broad class and say, "All CYP3A4 chemotherapeutic agents
are going to have the same safety profile."
And
that was one of the other reasons I emphasized and pointed out that the
docetaxel study may not be something that we can rest a lot of our faith on
because it had absolutely no effect on plasma levels.
I
would have anticipated at least a minimal effect, something that we could have
at least seen as a normal comparison. I
think we would have predicted approximately like a 15 percent effect.
CHAIRPERSON
CAMILLERI: Dr. Brawley?
DR.
BRAWLEY: Out of some ignorance, aren't
we dealing here not just with different drugs but also with different
polymorphisms of CYP? I mean, so that is
an entirely different variable.
DR.
DELLA'ZANNA: Right.
CHAIRPERSON
CAMILLERI: Did you want to expand on the
inference from your comment?
DR.
BRAWLEY: Well, I'm wondering if we need
to try to look at I guess if I were to put it into a simple question, are there
perhaps populations that I would define, not necessarily by race, maybe even
area of geographic origin, but define by the polymorphism of the p450 that they
have who might be dosed very differently with this drug or with some of the
other drugs that we are using.
DR.
JARUGULA: To address the polymorphism,
in general among the CYP 450 isozymes, the isozymes 2B6 and 2C9 are known to
have extensive polymorphisms. They are
poor metabolizers and tend to be metabolizers.
There
may be some information in the literature coming up recently on the
polymorphisms of various CYP3A components, but we don't have a good handle I
think on the polymorphisms of CYP3A, and this drug is mainly metabolized by
CYP3A4.
Among
the components that are to be given with the aprepitant which are
corticosteroid, dexamethasone, and 5‑HT3 antagonist
ondansetron, these, specifically 5‑HT3 antagonists, are less
prone to drug‑drug interactions because they have multiple metabolic
pathways.
So
I am not sure if there is any more information that can be added to address the
issue of the polymorphism.
CHAIRPERSON
CAMILLERI: Dr. Metz?
DR.
METZ: Yes. Thank you.
One
of the questions that FDA has asked us to look into is whether we think all 5‑HT3
drugs in the class should be considered the same, but after your presentation,
my understanding is that you would be less concerned with dolasetron than you
would with the other two 5‑HT3's. Can you confirm that? That is question number one.
Question
number two relates to anti‑fungal agents.
I think many of these patients develop thrush, for example, and end up
getting anti‑fungals. Nobody has
actually raised this as a specific concern, but I am wondering if you think
that should be something that should be looked at carefully.
DR.
JARUGULA: Regarding the first question,
the interaction with dolasetron, based on its multiple metabolic pathways, we
don't think that there will be a significant pharmacokinetic interaction. However, there could be a pharmacodynamic
interaction or there could be a different safety profile when aprepitant is
administered with the dolasetron, specifically as Dr. Della'Zanna
mentioned. Dolasetron is known to have
QT prolongation and other cardiac side effects.
Regarding
the second question about anti‑fungal agents, ketoconazole, which is an
important CYP3A4 inhibitor, actually significantly reduced the AUC of
aprepitant by about five‑fold.
That is quite a bit of significant interaction, and it is a concern that
needs to be brought out properly or adequately in the label.
CHAIRPERSON
CAMILLERI: Dr. Metz, is it fair to say
that the fungal infections don't usually happen in the first couple of days?
DR.
METZ: I have thought about that, but the
truth is we have got to realize these patients are going through multiple
cycles of chemotherapy and are going to be getting repetitive regimens. And you can certainly pick up your fungal
infection in an intervening period and come up for chemo in due course.
CHAIRPERSON
CAMILLERI: Thank you.
Dr.
Fogel?
DR.
FOGEL: I also have a question related to
the ketoconazole. The ketoconazole is a
very potent inhibitor of the 3A4 enzyme, actually much more potent than
aprepitant. Do you have any data on
ketoconazole effects on chemotherapeutic agents?
DR.
JARUGULA: As I presented in one of my
slides, there are two studies reported with ketoconazole. One study showed that the ketoconazole
increases the AUC of the irinotecan active metabolite by 100 percent. And the other study showed that ketoconazole
does not affect the PK of paclitaxel.
These are the two studies we have come across with the chemotherapy
agents with ketoconazole.
DR.
FOGEL: Can we use ketoconazole as a
surrogate for aprepitant effects?
DR.
JARUGULA: The problem in using
ketoconazole as a surrogate is that midazolam is a sensitive CYP3A4 substrate
for measuring these interactions.
If
you compare the interaction with midazolam for ketoconazole and the aprepitant,
aprepitant only results in a 3.34 change in AUC. But ketoconazole can go up to a 16‑fold
change in AUC.
But,
again, with chemotherapy agents, depending on the sensitivity of those agents
to the CYP3A4 isozyme, a change of two‑fold or even less than two‑fold
could be concerning in terms of its toxicity.
So
there is not adequate information in the literature to say or to rank these
chemotherapy agents in terms of their metabolism by CYP3A4. So that is a difficulty unless you study with
main chemotherapy agents that are known to be metabolized by CYP3A4. I would think that you may not be able to
credit the interaction.
CHAIRPERSON
CAMILLERI: Dr. McLeod?
DR.
McLEOD: I'm trying to solidify opinion
on how much we should care about the drug interactions in terms of the change
in blood levels of the aprepitant and not its effect on other drugs but,
rather, its change in blood levels.
Some
of the data that was presented, we tried to get this out from Dr. Petty during
the discussion, but there seems to be a fairly wide index, a therapeutic index,
with this agent.
I
wondered, with your review of the data, which is obviously more extensive than
you are able to present during the short presentation time here, whether you
had a feel for whether even a doubling or a halving of blood level would likely
change the place a patient would be on that sigmoidal affect curve that was
demonstrated during the applicant's presentation.
DR.
JARUGULA: Yes. Regarding the dose‑response of the
aprepitant, sponsor has investigated three dose regimens, 40/25, 125/85, and
375/250. Based on the trough concentrations
that you can expect from these dose regimens, you don't expect a significant
improvement in efficacy, going from 125/85 to 375/250.
The
efficacy is almost maxxed out at 125/85 regimen if that is your question. I can see where you're coming from there, but
if you are using rifampin or something like that.
If
your blood levels were decreasing, were cut in half, for example, I don't have
a feel from reading the data that was provided to us whether that is likely for
the efficacy to fall off the curve at that point. You know, there was a sigmoidal curve, and
there is quite a lot of variability shown, at least with the standard
deviation.
DR.
McLEOD: How about in the other
direction?
DR.
JARUGULA: As far as I know, in the dose‑ranging
studies, I think that's the only place where they have tested multiple dosage
regimens. And in the Phase III, only one
dosage regimen was tested.
For
the lowest dose regimen, 40 milligrams, 25 milligrams, the sponsor reported
that the efficacy was not maximal. However,
it was shown to be efficacious. But it
was not at the maximal response that you hope for.
CHAIRPERSON
CAMILLERI: Dr. Desta?
DR.
JARUGULA: But regarding how much
lowering of plasma levels would interfere with the efficacy, certainly rifampin
reduced the **blood levels by 11‑fold.
And that is a lot of change in the blood levels. The efficacy I think would be affected.
DR.
DESTA: In most of the presentations,
three of four is mentioned. I never
heard about three of five. And that is
polymorphic, actually. It could also
influence the drug interaction profoundly.
It could also influence some of the pharmacokinetics. That is one question for the company and for
you guys.
The
second question is you mentioned that dolasetron has multiple metabolites. And you would not expect any drug interaction
with the aprepitant. Is that correct?
DR.
JARUGULA: Yes, that is correct.
DR.
DESTA: Yes. If you have, for example, a poor metabolizer
which is not producing any enzyme 2B6 because it seems that 2B6 is the enzyme
which is metabolizing the active modifier by the carbonyl reductase, then if
you put on top of that like aprepitant, wouldn't you expect any significant
drug interaction in that respect?
DR.
JARUGULA: If that main metabolic pathway
is shunted to a different metabolic pathway, which is 2C8, it is possible that
you could see an interaction with aprepitant.
It is possible.
CHAIRPERSON
CAMILLERI: Is that a question about 3A5?
DR.
JARUGULA: The question regarding 3A5, in
the NDA data package, I haven't seen any information on CYP3A5 isozymes
specifically. If sponsor has anything
more to add, I don't know.
CHAIRPERSON
CAMILLERI: Ms. Hoffman?
MS.
HOFFMAN: I guess my question was fairly
similar. I just wondered if there was
data looking at further downstream mechanism, molecular mechanisms, and then
potential drug‑drug interactions from the downstream molecular changes as
well.
DR.
JARUGULA: That's a good question. As alluded to in the presentation, aprepitant
on chronic administration induces its own metabolism. And there is a conclusion in the NDA that
aprepitant induces CYP3A4 isozyme also.
So
that could lead to a different scenario of interactions where aprepitant might
induce the metabolism of the co‑administered drugs and result in lower
efficacy if it is administered chronically.
So that is a significant issue when this drug is going to be considered
for the chronic administration.
CHAIRPERSON
CAMILLERI: Dr. Proschan?
DR.
PROSCHAN: Yes. You mentioned the multiplicity issue with
respect to some of the secondary outcomes, nausea being one of them. It seems to me that there is a big
multiplicity issue with the adverse events as well, namely you are looking at
many different drugs, many different organ systems. It seems like it would be pretty likely that
you would find one of them with a nine to three difference.
DR.
DELLA'ZANNA: Right. We are not playing that down, and we realize
the numbers that we are talking about and the differences that we are talking
about are small.
However,
we are concerned that we don't have enough information to draw a conclusion,
and we have to work with the numbers that we have.
CHAIRPERSON
CAMILLERI: Dr. Cryer?
DR.
CRYER: One of the things that caught my
attention from the sponsor's presentation was this difference in adverse event
rates in the multiple‑cycle extension versus just cycle 1. And most of the data that you showed us with
respect to the adverse events were from cycle 1.
I
was wondering what sorts of patterns you might have observed with respect to
cycles 2 through 6 with specific regards to the adverse events.
DR.
DELLA'ZANNA: The serious adverse events
balanced out a little more during the multi‑cycle extension. Okay?
But one of the concerns I had regarding, for example, like vinorelbine,
we had a fair number of pulmonary problems that occurred. And if you removed those patients from the
multi‑cycle extension, then the number of patients exposed is also
smaller.
Overall,
most of the things they focused on which were the greatest differences were
during the cycle 1.
DR.
CRYER: In follow‑up to that, I
would like to follow up with the sponsor for that specific question. So I believe, Dr. Reines, on the very last
slide which you showed us that had to do with infections during cycle 1, I
don't remember the specific number, but it was the last one that you requested
to be shown, that was cycle 1 data.
Would you happen to have similar data for cycles 2 through 6 with
respect to infection?
DR.
DELLA'ZANNA: Can I just clarify one of
my concerns, too, which may not be able to be demonstrated on that slide? The slide that we are going to see is maybe
multi‑cycle extension data, but it is not broken down specifically to the
areas of concern that the agency has, which are specifically the individual
CYP3A4 chemotherapeutic agents.
Overall
I tried to include that in my presentation, that overall the incidence of
serious adverse events as a whole was similar between the two treatment
groups. It's only when we broke these
out and looked at the specific chemotherapeutic agents that we started seeing
some small but definite differences.
These differences are where we are focused on concerns.
If
we see another slide that shows that overall in cycle 2 through 6 that the
serious adverse events were the same, I don't think it's going to answer the
agency's concerns.
DR.
REINES: I don't think I have that same
breakdown of infections, but I can show the serious adverse events that
occurred. If I could have 509,
please? If we look at serious adverse
events over multiple cycles, the incidences were very similar between the two
treatment groups. And the more common
are indicated on this slide.
CHAIRPERSON
CAMILLERI: Okay. Perhaps just for clarification, Dr.
Della'Zanna, can you tell us a little bit more about the vinorelbine pulmonary
toxicity that concerns you? The specific
question I have is, is it just conceivable that there were more people with
lung cancer in the aprepitant group relative to the control arm?
DR.
DELLA'ZANNA: Overall the incidence of
cancers was pretty well‑balanced within each group. So to say that this population had a higher
prevalence of lung cancer that would have resulted in this bias I don't think
was what occurred.
CHAIRPERSON
CAMILLERI: Can the sponsor specifically
answer that question? Among the people
with pulmonary or respiratory problems in the vinorelbine‑treated group,
were there more in the aprepitant group who happened, for instance, to have
been lung cancer patients than in the other group?
DR.
DELLA'ZANNA: Most of the serious
respiratory or fatal respiratory insufficiencies occurred at the same
site. So I am not sure as far as the
numbers specifically for the balance of vinorelbine for lung cancers.
DR.
REINES: Could I talk about those
patients, the vinorelbine patients, for just a moment? I want to emphasize that myelosuppression is
the dose‑limiting toxicity with this agent and that we did not see an
excess there.
In
terms of the patients with respiratory insufficiency, these did occur at one
site, as was mentioned. At this site, we
specifically spoke with the investigator.
These were all patients with lung cancer, although there was not an
imbalance of lung cancer between the aprepitant and control groups.
However,
these patients did not have the respiratory insufficiency typical of
vinorelbine; that is, the acute dyspnea that occurs within a day or two. These were chronic patients. And the investigator said they died of their
lung cancer. They did not have any sort
of bronchospasm or acute dyspnea.
CHAIRPERSON
CAMILLERI: Dr. Brawley, did you have a
question? Go ahead, Mike.
DR.
PROSCHAN: I had a question on a
different topic. I don't know if it is
appropriate, but it was about the nausea.
The rescue medication, is that something that is given at the time
someone is feeling nauseous? Is it given
like if I am nauseous today, I get it and then two days later, I get it again
if I am nauseous again or is it given from then on?
DR.
DELLA'ZANNA: No. The rescue medication was administered upon
complaints of nausea. It wasn't
something that was scheduled. As a
matter of fact, the firm actually while still blinded analyzed the use of
"rescue medication" to make sure that it was appropriately
given. And they did a good job isolating
those patients out to make sure that it wasn't just given prophylactically
where somebody said, "Oh, I might get nauseous."
DR.
PROSCHAN: It sounds like there are a
fair number of people who got rescue medication and checked or put a mark that
is less than five on that VAS score. I
am wondering if they just didn't remember.
I mean, they had to be rescued from something. Maybe they didn't know that even if you don't
vomit, you could be nauseous.
DR.
HORGAN: Right. We were very careful about the instructions
that we proffered the patients. I think
one of the key issues that one has to bear in mind and that maybe didn't come
out in my presentation is emesis is easy.
The
patients had a diary. They recorded the
emetic event. When they took rescue,
they recorded the time of the rescue event.
Nausea is from one's own personal experience a much different entity. The patients were taking daily ratings of
their nausea experience over the preceding 24 hours. And so the correlation between their actual
experience of nausea on a given day is different than it was for the other
efficacy elements: emesis and rescue.
We
did look carefully to corroborate the fact that the patients were actually
taking rescue for nausea. And we saw
that the patients that took rescue did, in fact, have higher nausea ratings
than the patients who did not take rescue.
So we are confident that it was an effective surrogate of the experience
of nausea for the patients.
Does
that address your question adequately?
DR.
PROSCHAN: Yes.
CHAIRPERSON
CAMILLERI: Ms. Cohen?
MS.
COHEN: Maybe you already presented it,
but how often did people in your clinical trials have to take rescue medication
as a percentage?
DR.
HORGAN: We presented the data in my
presentation that actually showed the percentage of patients who took rescue at
least once. That was a component of our
primary endpoint. So we had approximately
20 to 25 percent of the patients in both of the Phase III trials took rescue at
some point.
MS.
COHEN: Did you delineate between one,
two, three, or four or just ‑‑
DR.
HORGAN: For the purposes of the primary
endpoint, we did not, but we did enumerate all of the occurrences of rescue
therapy. And we saw that consistently the
patients in the control group were taking more rescue. They were taking rescue more frequently than
the patients in the aprepitant treatment group.
CHAIRPERSON
CAMILLERI: Do the committee members have
any other questions?
(No
response.)
CHAIRPERSON
CAMILLERI: If not, this is a good time
for us to take a break. We plan to be
here again at 1:10 so that we can start the proceedings for the afternoon. Thank you very much.
(Whereupon, at 12:15 p.m., the
foregoing matter was recessed for lunch, to reconvene at 1:10 p.m. the same
day.)
A‑F‑T‑E‑R‑N‑O‑O‑N S‑E‑S‑S‑I‑O‑N
(1:12
p.m.)
OPEN PUBLIC
HEARING
CHAIRPERSON
CAMILLERI: Okay. Good afternoon. We are now at the stage in the proceedings
where we would invite the open public hearing or presentation. And we have not yet received any notification
of such a presentation. Is there anybody
from the public that wishes to make such a presentation at this time?
(No
response.)
CHAIRPERSON
CAMILLERI: If not, I think we should
move on to the next item. Really, it is
to ask Dr. Justice to address the committee and give us the charge.
CHARGE TO THE
COMMITTEE
DR.
JUSTICE: Well, our charge to the
committee really is brief. And, as I
discussed this morning, now that you have heard the presentations, we would
appreciate your discussion and vote on those questions.
As
you can tell from the questions and the presentations, we are particularly
concerned about the potential for drug‑drug interactions, particularly
with chemotherapy drugs that are metabolized by CYP3A4.
So
that is basically all I want to say. I
think we can move to the committee's discussion of the questions and votes.
CHAIRPERSON
CAMILLERI: Thank you very much. Are we going to present the questions or are
they on a slide?
DR.
JUSTICE: They are on a slide and in your
handouts, I think, as well.
CHAIRPERSON
CAMILLERI: Okay. Just to remind the committee members, as we
address each question, if there are areas of clarification where we still wish
perhaps the sponsor to give us some further information for clarification, I
think we still have an opportunity to do so.
Also,
we will need to go around the table. And
each individual member of the committee will be asked to give a vote yes or
no. If I forget to specify your name
before you give your vote, please remember to give your name so that it is
there for the record.
Okay. The first question, has the aprepitant
regimen been demonstrated to be effective in the prevention of nausea and
vomiting in the acute phase and in the delayed phase?
I
guess the first thing I need to ask is are members around the committee wishing
to have some further clarification on any of these issues? Dr. McLeod?
DISCUSSION OF
QUESTIONS
DR.
McLEOD: I think one of the issues that
has come up is the issue of effectiveness against vomiting versus effectiveness
against nausea.
I
would like some further clarification of this because the question that is
going to be posed to us includes both.
And so I wouldn't want to have to err on one side or the other without
being clear if we can divide the question or at least understand specifically
what is on the table there.
CHAIRPERSON
CAMILLERI: Okay. I think we are going to have some restricted
time for some clarification from the sponsor with regard to the specific point.
DR.
HORGAN: I think it's compellingly clear
that our data shows that we have efficacy in the prevention of both nausea and
vomiting with our primary endpoint. I
would like to show slide 96, the primary endpoint of complete response being a
patient having no emesis and taking no rescue therapy and highly significant
advantages for the aprepitant regimen with the primary endpoint ‑‑
DR.
HOUN: Okay. I'm not sure where. The question on the table was how we should
ask the question should be divided. I am
not really sure if people are wanting to go through show us the data again
about this before we vote.
May
I ask, Dr. McLeod, is it that you are asking in terms of how you should
vote? You are questioning whether the
"and" phrase, "nausea and vomiting in acute phase,"
"nausea and vomiting in delayed phase," should it be voted as nausea
and vomiting or you were asking whether it should be separated as nausea in the
acute phase, vomiting in the acute phase?
Is that your question?
DR.
McLEOD: I guess so, yes. I mean, I don't know what the procedure is in
this context, but certainly the data for one of those areas is dramatically
more compelling than the other.
I
didn't know which way we probably are going to vote; either way you want
it. But I just wanted clarity that if we
have to be **100 percent for both of those indications, then that may sway some
of the votes versus whether we disbelieve that it is a good antiemetic, as
opposed to anti‑nausea, agent.
CHAIRPERSON
CAMILLERI: So let me just ask for a
clarification from Dr. McLeod. Would it
make it easier if the question were posed, is this medication effective for
vomiting in the acute phase and the delayed phase? That's one question.
Second
question, is this medication effective or have the data been demonstrated that
it is effective in the context of nausea in the acute phase and the chronic
phase, or the delayed phase?
DR.
McLEOD: Yes. I think that's really getting to the gist of
what I am trying to ask because practically speaking, it doesn't matter. You don't treat nausea and vomiting
separately. You give therapy for them
together.
Going
by the data that has been presented, the data is certainly much stronger for
vomiting than it is for nausea.
CHAIRPERSON
CAMILLERI: I actually think that I am
trying to understand how that can be clarified further by data that the sponsor
may have. I think there has been ample
opportunity to tell us what the primary endpoint is.
I
guess what the people around the table might need to decide for themselves is
whether the complete response in the lack of use of antiemetic medication
safety constitutes a surrogate for the symptom of nausea.
I
think that is what it comes down to ultimately because the nausea, no
significant nausea and no nausea demonstrated by the VAS of ‑25 or up to
5, the data had been presented. And I
don't think that it will be useful to present them again.
Is
that clear?
DR.
ERB: I do think that there is an
opportunity here to clarify a little bit more on the nausea and response, too,
to the impact on patients' lives, which I think is an equally important measure
that has not been presented so far.
CHAIRPERSON
CAMILLERI: Okay. Dr. Horgan, let's have two minutes with one
pivotal slide to convince us more than what we have just addressed here?
DR.
HORGAN: Well, I think that the single
slide that I would like to show is slide 203, which just emphasizes that for
the data that we collected, the continuous variable of nausea over the entire
spectrum, maximum nausea ratings, we saw a consistent advantage for aprepitant,
which was statistically significant. The
data was similar for both the individual studies and was statistically
significant from one of those studies.
So,
in addition to the data that I have shown for this particularly troubling
symptom, we also had data assessing the impact of nausea and vomiting on
patients' daily lives.
Now,
the committee hasn't seen that data, but I think that provides compelling
additional information that illustrates the consistency of the effect that we
saw in the prevention of nausea. And
also it provides information on the clinical significance of the effects that
we saw.
So
I think that it may be valuable to see for the committee to have an opportunity
to see that data. My colleague can
present that.
CHAIRPERSON
CAMILLERI: I think that it probably
isn't necessary at this stage. Thank you
very much.
I
think we can go back to Dr. Houn's question.
DR.
HOUN: I think that if you do want to
split them out, you can, but we would want you to vote also on this question,
the combined.
CHAIRPERSON
CAMILLERI: That's fine. We can certainly address the question. Are there any specific questions or questions
of further clarification pertinent to question number 1 that the members of the
committee wanted to address? Dr. Metz?
DR.
METZ: Yes. I think we need to define the regimen because
that comes up in later questions, but when you say, "Has their regimen
been demonstrated?" that is the study drug regimen used in each of these
pivotal trials, one with granisetron, one with ondansetron. Is that correct?
DR.
JUSTICE: That's correct.
DR.
LaMONT: Yes. I would like to hear from the clinical
oncologists about the separating out of these symptoms because it seems to me
that they are virtually inseparable.
DR.
JUSTICE: I think there is not a
significant difference.
DR.
BRAWLEY: I see perhaps some more of a
difference than Dr. Kelsen, but I read this really as more of a quality of life
question. I would just say, has the
regimen been demonstrated to be effective in improving the quality of life in
the acute phase and in the delayed phase?
CHAIRPERSON
CAMILLERI: So I think that the consensus
is that we put these back together again.
And that is the question the agency really wants us to answer.
Are
there any other issues of clarification before we start to take votes? Ms. Cohen?
MS.
COHEN: I think that you said that less
than 25 percent of rescue therapy was used; is that correct, when I asked
before?
DR.
HORGAN: Yes. Approximately 25 percent of patients used
rescue therapy.
MS.
COHEN: Can I say something? You know, a lot of you are delivering
physicians. And you have to deal with
the anguish of people having nausea and having vomiting.
As
a consumer member, I think there is another dimension that we need to be
protected also. And I think since you
have to deal with the end result of very sick people, your compassion is very
strong. I would like to know that there
is a balance here in the drug‑drug reaction. And not studying it, to me, I am very
concerned.
And
that is my speech.
CHAIRPERSON
CAMILLERI: Thank you.
Other
issues related to question number 1 or are we prepared to go around the table
and answer the question? Michael?
DR.
PROSCHAN: So the decision was to do two
things, the combined and then the nausea separately or just the one thing
combined?
CHAIRPERSON
CAMILLERI: I think the decision is that
we go back to the original question as posed by the agency and address it
separately for the acute phase and the delayed phase.
DR.
PROSCHAN: So it is just nausea,
then? That is the ‑‑
CHAIRPERSON
CAMILLERI: No. It is the combined package of prevention of
nausea and vomiting.
Okay. I think not seeing any other hands coming up
or questions being posed, I would like the committee to start taking a vote on
this specific issue. So let's just break
this up into two bits again just so that we are clear.
The
first question is, has the aprepitant regimen been demonstrated to be effective
in the prevention of nausea and vomiting in the acute phase? I am going to start asking Dr. Proschan. Would you give us your vote?
DR.
PROSCHAN: I would vote yes.
CHAIRPERSON
CAMILLERI: Dr. Desta?
DR.
DESTA: I will vote yes.
DR.
McLEOD: Howard McLeod. Yes.
DR.
BRAWLEY: Otis Brawley. Yes.
DR.
KELSEN: Yes.
CHAIRPERSON
CAMILLERI: That was Dr. David Kelsen,
yes.
DR.
LaMONT: LaMont. Yes.
DR.
LEVINE: Levine. Yes.
DR.
METZ: Metz. Yes.
CHAIRPERSON
CAMILLERI: Camilleri. Yes.
DR.
CRYER: Cryer. Yes.
DR.
FOGEL: Fogel. Yes.
MS.
COHEN: Cohen. Yes.
MS.
HOFFMAN: Hoffman. Yes.
CHAIRPERSON
CAMILLERI: Okay. We can address the second question now or
part 2 of question number 1, has the aprepitant regimen been demonstrated to be
effective in the prevention of nausea and vomiting in the delayed phase?
DR.
PROSCHAN: We have to vote or is there a
discussion of that? Are we at the voting
stage on that?
CHAIRPERSON
CAMILLERI: I am happy to entertain
further discussion. This is a very
important point. Thank you, Dr.
Proschan.
DR.
PROSCHAN: Okay. Yes. I
think it is difficult to tell because of the fact that the rescue medication
could have saved them or they may have not thought about the fact that the
rescue medication meant that they did have nausea. And once they took the medication, they
didn't feel that they had it anymore. So
I think it is difficult.
The
other issue is much cleaner to answer.
CHAIRPERSON
CAMILLERI: Can I ask for a clarification
perhaps from the agency side? It is my
impression that one of the presentations said that rescue medication was used
in 28 percent in the control group and 18 percent in the aprepitant group. Is my recollection correct?
DR.
DELLA'ZANNA: That's correct. I am not sure if you are understanding what I
was also trying to emphasize. Their
complete response in the overall phase as well as acute and delayed phases
excluded the use of rescue therapy.
So
if you just focus on the primary endpoint as well as the secondary endpoints of
complete response, we** are ignoring the use of rescue therapy because they
didn't have any.
So
I don't have as much of a concern regarding that for the delayed phase because
it was statistically significant without the use of rescue therapy and then in
support of their findings that the use of rescue therapy now was no longer
considered a responder and the patients had failed the primary endpoint, the
use of rescue therapy was used more frequently in the standard therapy group.
I
don't know if that better answers what you were saying.
DR.
PROSCHAN: When you look at whether they
had nausea or not, their scores if they had the rescue therapy are likely to be
different than their scores if they didn't have the rescue therapy.
So
I still think there is a problem. It is
certainly much less clean to try and answer that question tan the first
question.
CHAIRPERSON
CAMILLERI: Other clarifications needed
on this point? Yes. Go ahead, Dr. Desta.
DR.
DESTA: Yes. I'm not sure whether a single dose or a
multiple dose is recommended. I mean, if
we see the figure 7‑3, it seems that the single dose does it. I don't know whether there is a difference
between the 52 and the 43 percent difference in the delayed effect.
So
I am not sure about the dosing interval.
Is a single dose enough?
According to this figure, it seems that a single dose is also doing
that.
CHAIRPERSON
CAMILLERI: Dr. Cryer is indicating to me
that the five‑day results are indicated here. And presumably that is what the sponsor is
recommending, that this would not just be a one‑day treatment, but it
would go on for three days.
DR.
HORGAN: The Phase III regimen.
CHAIRPERSON
CAMILLERI: According to the Phase III
regimen.
Maybe
I could have a clarification from the agency.
Is it possible to answer yes to this question but then to make
recommendations on the indication? I
think there is some discomfort with regard to the over‑encompassing
conclusion that there is about nausea here.
I think there is a practical discomfort around the committee members.
So
is it, in turn, inconsistent or is it still possible to work with a general
statement in response to question number 1 but to clarify the implications
perhaps clearly in the indication?
DR.
JUSTICE: Certainly if you can clarify
it, we would appreciate it greatly.
CHAIRPERSON
CAMILLERI: Dr. Fogel and then Dr.
Levine.
DR.
FOGEL: As we are going on, I am getting
more and more confused. So I guess my
question is for the agency. In this
study when the data was presented and then in the initial presentation by the
agency, there was agreement that the delayed phase was effective.
If
I understood correctly, there is a significant reduction in the use of rescue therapy
in the delayed phase. And, as I have
been listening to the discussion, it seems to be revolving around the VAS
scores, where there does not seem to be a significant difference. Is that correct?
DR.
DELLA'ZANNA: Well, it is a little more
than just the VAS scores. Historically
we have used and we are concerned about applying an indication that this could
be used for nausea. Okay? Independently if you look at that endpoint,
it doesn't become significant.
I
agree with Dr. Brawley that it is difficult or impossible to separate nausea
and vomiting from one another. And I
agree in practice that vomiting is the progression of severe nausea. Historically we have to also be concerned
with the potential that this could be used as an indication for nausea. And because of that, that is the only reason
we separated these out as a question for the committee.
We
have similar concerns as far as yes, we agree it was significant in the
overall, complete response overall, phase, acute phase, and delayed phase. But if you looked at it independently for
nausea, it wasn't as convincing.
The
**firm has done a very good job and a good argument stating that the use of
rescue therapy is a surrogate for the degree of nausea. We have not used that in the past. And so we are setting a precedent.
DR.
FOGEL: The question I have about the
nausea scores, it was my understanding from the previous discussion that when
people marked their score, it was if they took rescue therapy, they still got
to mark a score. Is that correct?
DR.
HORGAN: Yes.
DR.
FOGEL: And when you calculated the
number of people who were less than 5 and less than 25, you did not exclude
those who had not already taken rescue therapy.
DR.
HORGAN: Absolutely. Every patient in the study was making daily
nausea recordings, irrespective. And
that is one of the key issues, that despite the fact that patients in an active
control group were taking more rescue therapy, we consistently found an
advantage with the aprepitant treatment in our nausea VAS scores.
DR.
FOGEL: Did you do a subset
analysis? Since you have been slicing
the data a number of different ways, did you do a subset analysis where you
excluded those who took rescue therapy and just looked at the nausea scores?
DR.
HORGAN: We didn't think that was a valid
way to look at it from the perspective of the syndrome of chemotherapy‑induced
nausea and vomiting because there are complex relationships between emesis and
nausea or rescue and nausea. So we
focused on looking at the total patient population in our assessments of nausea
and also rescue therapy, though we did note that rescue therapy was associated
with higher nausea scores in general.
CHAIRPERSON
CAMILLERI: Dr. Levine?
DR.
LEVINE: My question is really for the
agency. I think it is marginal, the
effects on nausea, but I think what I am concerned about is in the labeling. I don't have a problem with labeling that
might even say "highly emetogenic," but I think if we put the word
"nausea" in the label at all eventually, that this drug is for
nausea, it may be another subject. But
forgetting the off‑label possible use, forgetting that it is limited to
chemotherapy, I am concerned in that delayed period, that doctors will be
looking at what they think is a good drug for nausea. It is that simple.
And
I just wondered, are we mandated in any reason?
I think it is a sticky wicket to try to get into the word
"nausea." I agree with Dr.
LaMont. They are linked together in
patients. I don't have a problem with
that. But I think if it is going to come
to putting a label on this with nausea, I would be hesitant about it.
CHAIRPERSON
CAMILLERI: Dr. Brawley?
DR.
LEVINE: Can they clarify that? Can the company clarify whether this is going
to be in the label or not?
DR.
HOUN: Well, this is what they are
proposing for labeling. I imagine this
is what they desired, nausea and vomiting.
They are saying yes. I think we
are looking for your recommendations.
You know, I think there are safety concerns, as you know, as we will
discuss more this afternoon.
I
think, actually, if you can help us understand.
Our standard is safe and effective as labeled, but that is for
approval. But to stay on the market, it
is safe and effective as used because drugs run into trouble if they are used
inappropriately.
So
I am interested in GIs' as well as other docs', cancer docs' opinion on what
are the problems we might run into in real use.
CHAIRPERSON
CAMILLERI: Dr. Metz?
DR.
METZ: Can I just clarify something? My understanding is what the company is
asking for is a regimen that is going to be given to people up front who are
going to be getting chemotherapy to prevent them from getting chemotherapy‑induced
nausea and vomiting, which is bad. This
affects a lot of people and can be reduced by 20‑plus percent with this
particular regimen.
Giving
PRN drug for nausea in patients who happen to have received chemotherapy
beforehand to me is going to ultimately be a big off‑label use unrelated
to what we are talking about here today.
If we talk about chemotherapy‑induced nausea and vomiting that you
are going to prevent with this regimen, you can't separate the nausea and
vomiting. That is the syndrome.
But
if you want to ask us as a separate use, are we worried about off‑label
use for another indication, whether it is in patients who receive chemotherapy
or patients with totally unrelated disease states, that is a different question
entirely.
This
question, as I read it, is the CINV syndrome.
And you have got to have the two together. And personally I think it affects the acute
phase, and I think it affects the delayed phase.
CHAIRPERSON
CAMILLERI: Dr. Brawley?
DR.
BRAWLEY: Yes. I have a couple of questions for the
company. They are very brief. As I look at the data, ‑‑ tell me
if I am wrong ‑‑ when you look at the randomized trials of people
taking aprepitant, there is less use of breakthrough medications or salvaged
anti‑vomiting and anti‑nausea medication in people who are on
aprepitant versus not on aprepitant. Is
that correct?
DR.
HORGAN: That is correct.
DR.
BRAWLEY: Okay. Now, of people who end up taking breakthrough
medications, even though they are on aprepitant, is there evidence here that
their quality of life is better, even though they are taking aprepitant and the
breakthrough medications, when compared to individuals who are not taking the
aprepitant?
CHAIRPERSON
CAMILLERI: I guess I am going to allow
you to show that quality of life slide after all.
(Laughter.)
DR.
HORGAN: We didn't break it out. We looked at the global patient
population. My colleague will show you
that data assessing the impact of nausea and vomiting on patients' daily lives.
DR.
BRAWLEY: Sorry.
CHAIRPERSON
CAMILLERI: That's okay. Thank you.
DR.
MARTIN: Good afternoon. My name is Allison Martin. I am from the Epidemiology Department at
Merck Research Laboratories.
Prior
to showing the results of the quality of life data, I would like to give a
little bit of background about the questionnaire so that you are fully informed
about how we collected this data.
Slide
1602, please. So, as you know, the
treatment goal for the aprepitant program was to prevent nausea and vomiting
following chemotherapy. As a corollary
goal, we wanted to assess the impact of nausea and vomiting on patients' daily
lives and ideally eliminate any impact on their lives. And so we use the functional living index
emesis questionnaire, which is a validated nausea and vomiting‑specific
measure to assess the impact of these symptoms on patients' daily lives.
The
questionnaire contains 18 items, 9 of which refer to nausea, 9 of which refer
to vomiting, which are 2 separate domains.
The questionnaire was given to patients where they were asked to
complete the questionnaire on day six, and it had in cycle 1 with a five‑day
recall.
So
basically it was asking the patients to rate the extent of the impact on the
items shown on the bottom over the past five days. As you can see, it contains functioning
items, such as enjoying meals daily, functioning household tasks, spending time
with family and friends, et cetera.
The
pre‑specified endpoint, though, that was used for this questionnaire was
a dichotomous endpoint. It was similar
to the nausea visual analog scale. This
is also the patients were making their ratings on a visual analog scale, which
ranged from one, which is a great deal of impact, to seven, not at all or no
impact.
The
score, an average item score, greater than six was predefined as no impact on
daily life because this is the uppermost bucket where patients were placing
their marks anchored by not at all.
The
next slide, please. This slide presents
the results from the two Phase III protocols on the total score of proportion
of patients in protocols 052 and 054 reporting no impact on daily life. So, as you can see in both protocols 052 and
054, a significantly greater proportion of patients in the aprepitant‑treated
group reported no impact on daily life.
Can
I have 1605? This is the same data, but,
then, also included is a combined analysis of the two protocols, which was with
nominal p values here, which, again,
it shows the consistency of those data.
To
head off Dr. Proschan's next question, can I please have slide 1606? This shows the cumulative distribution of
these average slide scores based on the total score.
The
way this works is the vertical axis is the percent of patients. The horizonal again is the scale that the
patients were using to mark their responses.
We have drawn in here the six cutoff that we used.
As
you can see, over the full distribution, almost over the entire distribution,
the aprepitant‑treated patients had significantly greater scores. If you look at here, this is the 64 percent
on the total score in the control group who had a score of 6 or greater versus
the aprepitant group, which had a score of 74 percent who had a score of 6 or
greater. Again, on slide 1607 is
protocol 054, which shows that these data are consistent.
The
last thing that I will show is slide 1614, which, as Dr. Kevin alluded to in
his presentation and what I had mentioned earlier that this questionnaire does
contain two domains, a nausea domain and a vomiting domains, the analyses here
show ‑‑ this is the results from protocol 052; 054; and, again,
combined, and this was a post hoc analysis.
These are nominal p
values. But, as you can see, the data
are consistent that we were superior to the control group in both the nausea
domain and the vomiting domain across the two studies and in a combined
analysis.
So
overall I think these data are highly consistent with our clinical efficacy
endpoints. And it shows that the
aprepitant‑treated patients had a benefit in terms of their ability to
maintain their functioning in that five days following chemotherapy, during a
period when they would expect to have debilitating symptoms.
CHAIRPERSON
CAMILLERI: Dr. Brawley, any
supplementary question?
DR.
BRAWLEY: No, sir. Thank you very much.
CHAIRPERSON
CAMILLERI: Okay. Dr. Della'Zanna?
DR.
DELLA'ZANNA: Okay. I don't want to complicate this whole
discussion any more than we already have, but I do want to point out a couple
of things in response to the firm's presentation.
As
far as the impact on daily life in the overall phase, which was a predefined
analysis, when the agency performed what they considered the appropriate
multiplicity adjustment, including all predefined secondary and exploratory
analysis, these p values were not
significant. For study 054, it was
0.06. And for study 052, it was 0.25.
I
don't want to distract from the focus of this question. I think we kind of are going in a little more
detail than necessary to make our decision.
But I don't want necessarily to put all of our support on the data that
was just presented.
CHAIRPERSON
CAMILLERI: Dr. Michael Proschan?
DR.
PROSCHAN: Yes. You know, one thing that one could do is say,
"Okay. Everyone who took rescue
medication would have had nausea if they hadn't taken it." That's one way of looking at it. And if you make that assumption, then
effectively your endpoint is either nausea or rescue medication.
Now,
that wasn't quite one of their secondary endpoints. I see everything except that on here. And I am wondering if that analysis was done
and what the results of that were.
I
mean, you could make various assumptions.
You could assume everyone who goes on rescue medication would have had
nausea or 80 percent of those would have had nausea. And if it's the case when you look at nausea
or rescue medication, that is still significant, then that would be more
evidence. I don't know if they have
that.
CHAIRPERSON
CAMILLERI: Have we got a quick answer to
that question?
DR.
DELLA'ZANNA: I can interject on that a
little bit and probably answer your response in a way you will like.
(Laughter.)
DR.
DELLA'ZANNA: They did. With blinding, they analyzed and removed the
"rescue therapy" that was inappropriately given as prophylaxis. So they pretty much did what you were just
recommending. And the people who
received or were counted as rescue therapy received it because they had
established nausea.
So
I know what you were saying as far as people who receive rescue medication, 20
percent were nauseous. Now, we can
almost assume that the people who received rescue mediation, 100 percent were
complaining of either nausea or vomiting.
DR.
PROSCHAN: Right. What I am getting at is what percentage of
those would have had a VAS score bigger than five because that is the real
question. If 100 percent of them would
have had a VAS score bigger than five, then essentially what it comes down to
is looking at the endpoint of either rescue medication or nausea.
And
if that is highly significant or even lowly significant, that is some evidence.
DR.
HORGAN: I think the best that we can do
to address your concern is just show what the relationship was in the patients
who did take rescue and what their visual analog scale scores were. We weren't able to because of the daily
nausea ratings define the precise relationship, but we can show, slide 303 ‑‑
DR.
PROSCHAN: I'm sorry, but you have all of
these secondary endpoints. I was just
wondering whether as a secondary endpoint, you looked at the endpoint of either
bigger than five on the VAS score or rescue medication.
I
mean, I see things that are very close to that under these secondary endpoints,
but I don't quite see that one. There is
a no emesis, no rescue, and maximum nausea less than five. But there isn't just no rescue and nausea
less than five. So I was wondering if
that were done.
CHAIRPERSON
CAMILLERI: Would it be fair to assume
that if people got rescue medication, their nausea score should have been
greater than five?
DR.
PROSCHAN: Well, my point is that if you
make that assumption, then the relevant question is for the endpoint of greater
than five or rescue medication, what are the results for that endpoint?
DR.
HORGAN: One of our composite endpoints
was total control. A patient in order to
have total control was no emesis, no rescue, and maximum VAS score of less than
five.
DR.
PROSCHAN: Right.
DR.
HORGAN: Would that address your ‑‑
DR.
PROSCHAN: No. I mean, I see things that are tantalizingly
close to what I want but not quite exactly.
DR.
HORGAN: Right. The other thing that I think is probably the
best thing that we can do to approximate your question is to look at the
relationship between the nausea ratings and the patients who took rescue. To illustrate ‑‑
CHAIRPERSON
CAMILLERI: Twenty seconds. Okay.
Then let's move on. I think we
have discussed this point. When I heard
the term "total control," I thought they were referring to Dr. Metz.
(Laughter.)
CHAIRPERSON
CAMILLERI: Okay. I think we have discussed this
sufficiently. We have clarified it. Let's get back to answer or at least respond
to the question. We are kind of doing
question 1B, has the aprepitant regimen been demonstrated to be effective in
the prevention of nausea and vomiting in the delayed phase? Dr. Proschan?
DR.
PROSCHAN: Yes.
DR.
DESTA: Desta. Yes.
DR.
McLEOD: McLeod. Yes.
DR.
BRAWLEY: Brawley. Yes.
DR.
KELSEN: Kelsen. Yes.
DR.
LaMONT: LaMont. Yes.
DR.
LEVINE: Levine. Yes.
DR.
METZ: Metz. Yes.
CHAIRPERSON
CAMILLERI: Camilleri. Yes.
DR.
CRYER: Cryer. Yes.
DR.
FOGEL: Fogel. Yes.
MS.
COHEN: Cohen. Yes.
MS.
HOFFMAN: Hoffman. Yes.
CHAIRPERSON
CAMILLERI: Okay. Thank you very much. I think we can move on to the second
question, is the designation of "highly emetogenic chemotherapy"
appropriate given the regimens used in the clinical studies? I think what I would like to do here is ask
our clinical oncologists to give us their opinion.
DR.
KELSEN: I think it is. Cisplatin is a very difficult drug to
take. Most of the patients, 80 percent,
have 70 milligrams per meter2 or higher. It is not fun to take 58 to 60 milligrams per
meter2. I think it is an
emetogenic regimen.
DR.
BRAWLEY: I would totally agree.
CHAIRPERSON
CAMILLERI: Does the committee require
any further discussion after the expert opinion? Dr. Fogel?
DR.
FOGEL: I have a question. The wording here is "highly
emetogenic." Can you explain
clinically is there any difference between highly and moderate emetogenic? I mean, is this an issue that we need to
address in great detail?
DR.
KELSEN: I don't think we need to address
in great detail. This is a highly
emetogenic regimen. I mean, in the days
before antiemetics existed for platinum, it was very difficult.
I
think by moderately emetogenic, they mean patients don't feel great, but
they're not crippled as they would be when you take platinum without any
coverage at all.
DR.
BRAWLEY: In the doses that we frequently
give, platinum before Reglan, very frequently people would become totally
dysfunctional. Nowadays most people are
able to function. Perhaps they can do
even better with drugs like this.
So
highly emetogenic in my mind means the person would be unable to function
without drugs to treat the condition.
CHAIRPERSON
CAMILLERI: Thanks, Dr. Brawley.
Dr.
Cryer?
DR.
CRYER: As I understand it, I think the
reason that we are being asked this question is that the previous standard to
determine or define highly emetogenic was a previous cisplatin dose of greater
than 100 milligrams per meter2 based upon ondansetron approval.
So
while I would like to get some clarification from Dr. Della'Zanna, when you
removed the people who were on the lower doses of cisplatin, I guess that was
less than 70. Did you say that it was
maintained?
DR.
DELLA'ZANNA: It maintained efficacy.
DR.
CRYER: Efficacy?
DR.
DELLA'ZANNA: Yes. And I should point out in the firm's behalf,
which I'm sure they will state if I don't now, that the dose itself has varied
in literature. If you look at the
ondansetron oral formulation, greater than 50 was utilized and described as a
highly emetogenic dose.
The
one reason I brought this up is for two points, that this dose has evolved and
that I just wanted to have clarification for future applications that this is
now an acceptable dose that we can use as a label. And that's it.
CHAIRPERSON
CAMILLERI: Thank you.
I
believe that we are ready to take a vote on this. This time I am going to start with Ms.
Hoffman.
MS.
HOFFMAN: Hoffman. Yes.
MS.
COHEN: Cohen. Yes.
DR.
FOGEL: Fogel. Yes.
DR.
CRYER: Cryer. Yes.
CHAIRPERSON
CAMILLERI: Camilleri. Yes.
DR.
METZ: Metz. Yes.
DR.
LEVINE: Levine. Yes.
DR.
LaMONT: LaMont. Yes.
DR.
KELSEN: Kelsen. Yes.
DR.
BRAWLEY: Brawley. Yes.
DR.
McLEOD: McLeod. Yes.
DR.
DESTA: Desta. Yes.
DR.
PROSCHAN: Proschan. I have no idea. So I am going to abstain.
CHAIRPERSON
CAMILLERI: Thank you. I think we can move on to the third question,
can the recommended regimen be expanded beyond that used in the clinical
studies to include the use of any 5‑HT3 antagonist as part of
the aprepitant regimen?
We
have to remind you that there were no studies with dolasetron. The studies that were presented in the
documents pertain to granisetron and ondansetron.
The
second part of the question, if not, what additional studies would you
recommend?
Now,
what I am going to ask, just to refresh our memories, Dr. Della'Zanna, can you
remind us what other studies you had suggested might be appropriate, additional
studies might be appropriate, as part of your presentation?
DR.
DELLA'ZANNA: Presently we have
intravenous studies on ondansetron and oral studies on granisetron. We do not have any oral information on
ondansetron. Now, agreeing with our PK
information, it is metabolized for multiple pathways.
So
the likelihood of a PK interaction is not that high. But the other interactions we can't
predict. As far as dolasetron, we have
no safety data whatsoever.
CHAIRPERSON
CAMILLERI: Okay. This is where we need our clinical
pharmacology colleagues also to help us out.
Would you like to make any statements or clarifications?
DR.
McLEOD: I believe Dr. Desta pointed out
that the way that dolasetron is activated and then metabolized does mean that a
fairly large fraction of the population is going to be relying on CYP3A4 for
the inactivation of the drug.
So
that while carbonyl reductase is involved, it's reactivating it. There are two enzymes, the CYP2D6 and 3A4,
that are then inactivating that metabolite, that active moiety.
As
Dr. Desta mentioned, ten percent or so of the general population are defective
in that pathway. And so they basically
are 3A4‑dependent. So it does
raise the question of whether there is a viable interaction at that point.
Without
any data, it is hard to decide whether it is relevant or not. It could have zero relevance or it could be
dramatically important.
I
also would like some clarification from probably Dr. Della'Zanna on the
robustness or whatever you can call it of the QT prolongation concerned with
dolasetron to see whether this is a true problem or one that is just a concern. If in practice this 5‑HT3
antagonist behaves as the other two, then I think we are just talking about
theory and not reality.
CHAIRPERSON
CAMILLERI: Dr. Della'Zanna, have you got
a response on QTc prolongation with dolasetron?
DR.
DELLA'ZANNA: I do not have access to
that information now to present.
CHAIRPERSON
CAMILLERI: Dr. Desta?
DR.
DESTA: I think with ondansetron, oral
drug interaction, I don't think there will be a big difference ‑‑
that is my opinion ‑‑ with ondansetron oral because we didn't see
it or they didn't see it with the other drug, which is exclusively a substrate
drug. So I don't think that will really
matter unless otherwise this drug inhibits 2B6 in a significant way because 2B6
is involved with also ondansetron.
The
other one I agree with Howard is how concerned are you or is there any dose‑response
relationship of dolasetron and QT interval prolongation? For example, in poor metabolizers, are there
any documented things or is there any drug interaction that really concerns
you?
Otherwise
if you take that drug, the metabolic pathway, which is shared by 3A, is
small. So if you block that, could we
get higher plasma concentration whereby we can have some QT interval concerns?
CHAIRPERSON
CAMILLERI: So if I am understanding you
correctly, Dr. Desta ‑‑ and excuse me. I am not a pharmacologist. Your first statement was that, even though
there haven't been studies with oral ondansetron, you as a pharmacologist, you
are quite reassured by the data that you see pertaining to the pharmacokinetics
of granisetron, another 5‑HT3 antagonist that shares the same
metabolic pathway as ondansetron. That
was the first point. Is that correct?
DR.
DESTA: Yes, correct.
CHAIRPERSON
CAMILLERI: Okay. Second point pertained to the question as to,
again reflecting Dr. McLeod's question, how much of a risk is there with the
dolasetron relative to QTc prolongation?
I am assuming that somebody from the company has something they really
want to say.
DR.
GRUNDBERG: I am Steve Grundberg. I am a medical oncologist from the University
of Vermont here as a consultant to the company.
We have done a lot of the developmental work on these various
antiemetics.
The
QTc question has been around for a long time.
I would have to say we are partly responsible for it because when we did
the Phase I's on dolasetron, it went to extraordinarily high doses and we were
able to see a QT change.
It
is not just the effect of dolasetron.
That is a common misconception.
It has also been described for ondansetron by both Gralla in New York
and by Benedict in Texas. There has
really not been any clinical significance to it. I don't know any oncologist who would not use
any one of these three drugs for that reason.
CHAIRPERSON
CAMILLERI: Dr. Kelsen, is that in
agreement?
DR.
KELSEN: I can't comment on the QTc
interval. That is not my area of
expertise. But the drugs are widely used
interchangeably.
I
guess the question here is if you're precedent‑setting and you are
looking a little bit down the line, if you didn't actually study the drug with
the other drug, what do you do?
CHAIRPERSON
CAMILLERI: I think that really
encapsulates our dilemma.
DR.
BRAWLEY: Pardon me. I never knew dolasetron existed until I
started reading this stuff. Granisetron
and ondansetron are very commonly used in my experience, but dolasetron I don't
think is a wide market share.
CHAIRPERSON
CAMILLERI: Go ahead, Dr. Metz.
DR.
METZ: It seems to me that from the
agency's point of view, people are concerned that unless you actually have
tested a specific agent, it is going to be a problem to make a statement going
forward.
But,
on the other hand, I think from the company's point of view, you have to sort
of say that we are going to look at representative examples of each class
because you cannot expect that you are going to do a study on every single
member of every single class.
I
was just very reassured by the most recent comment that these drugs are really
used interchangeably and that the QTc issue doesn't really pertain only to this
one particular agent.
CHAIRPERSON
CAMILLERI: In addition to that, I am
assuming that you are quite reassured that dolasetron is not primarily
metabolized by the 3A4 pathway.
DR.
McLEOD: Well, in 90 percent of the
people out there, there are two enzymes degrading the drug. So you knock out 3A4 and you've got 2D6 to
pick up the slack. In ten percent of the
population, at least in theory, you would predict they would be very reliant on
3A4.
It's
the consequence of that that is unclear to me.
If you alter the 3A4 metabolism of the active metabolite of dolasetron,
is that a big issue? I don't know the
answer to that.
CHAIRPERSON
CAMILLERI: Very brief comment.
DR.
PETTY: A very brief comment regarding
dolasetron. Dolasetron** is cleared
primarily by CYP2D6. Although it is not
in the label, there is reference in documents available by Freedom of
Information to indicate that poor metabolizers of CYP2D6 had a roughly two‑fold
increase in their AUC of hydrodolasetron and in patients who received verapamil
and diltiazem, which would have comparable 3A4 inhibition to aprepitant. There was no effect on hydrodolasetron
clearance.
CHAIRPERSON
CAMILLERI: So do you want to interpret
that for clinical gastroenterologists?
(Laughter.)
DR.
McLEOD: Since we're on record, I will
give a formal interpretation. It looks
like if you take patients who are deficient in 2D6 based on what was just
stated, if you have the two enzymes that degrade the drug, the active
metabolite, if you take patients who have one of them knocked out because of
genetic abnormalities and you then inhibit or alter in any way, inhibit or
induce on the examples he gave, the 3A4 component, the remaining component,
there were not dramatic changes in either the pharmacokinetics or the toxicity
profile. So the statement that was made
suggests that in those people that we were worrying about, it is not going to
be an issue.
CHAIRPERSON
CAMILLERI: Thanks for that
clarification. Dr. Fogel?
DR.
FOGEL: I just want to make a comment
about QTc intervals in studies since we are going to be precedent‑setting. One of the things we learned from cisapride
is that if you have electrolyte abnormalities or concurrent illnesses or
comorbid conditions, your risk of having fatal arrhythmias tends to be
increased.
Since
we are going to be dealing with patients who are off studies, not protocols,
who are going to be very sick, who get these regimens, I think we need to be
databased in any decisions that we make.
CHAIRPERSON
CAMILLERI: Thanks for the comment. Other discussion on this point or
clarifications requested?
(No
response.)
CHAIRPERSON
CAMILLERI: If not, I think we should
move ahead to try to answer the first part of this question, can the
recommended regimen be expanded beyond that used in the clinical studies to
include the use of any 5‑HT3 antagonist as part of the
aprepitant regimen? Dr. Proschan?
DR.
PROSCHAN: This is another ‑‑
DR.
McLEOD: Let's start on that side.
DR.
PROSCHAN: This is another one where I
think I have to abstain because I think it takes clinical judgment. And I have at most statistical judgment.
CHAIRPERSON
CAMILLERI: Dr. Desta?
DR.
DESTA: Desta. Yes.
DR.
McLEOD: McLeod. Yes.
DR.
BRAWLEY: Yes with a request for post‑marketing
studies.
CHAIRPERSON
CAMILLERI: That was Dr. Brawley.
DR.
KELSEN: Kelsen. Yes.
DR.
LaMONT: LaMont. Yes.
DR.
LEVINE: Levine. Yes.
DR.
METZ: Metz. Yes.
CHAIRPERSON
CAMILLERI: Camilleri. Yes with a request for further studies.
DR.
CRYER: Cryer. Yes.
DR.
FOGEL: Fogel. No.
You have at least one 5‑HT3 receptor that has been
approved that has been shown to be safe and effective. I think unless you have additional data, you
should not generalize. Even though other
combinations may very well be safe, you just don't have the data at this time.
MS.
COHEN: Cohen. No. I
think this is precedent‑setting.
If there is another study, we shouldn't be making these decisions. And there are consequences, and there is not
any data. This rush to publish is very
frightening to me.
MS.
HOFFMAN: I'm tossing back and forth
here. I am going to go with no with
further dolasetron studies recommended.
CHAIRPERSON
CAMILLERI: Thank you.
Have
we recorded that for the record? Thank
you.
The
second part of that question was, what additional studies would you
recommend? Was it, Dr. Brawley, you
recommended some additional studies?
DR.
BRAWLEY: Yes. I would like to see some pharmacologic
studies with dolasetron and EMEND. very much as we saw with ondansetron and
granisetron.
CHAIRPERSON
CAMILLERI: I am assuming that you are
happy with the oral ondansetron story.
DR.
BRAWLEY: Yes, I am happy with the oral
ondansetron study. Actually, Dr.
McLeod's conversation a little earlier made me much more comfortable with
approval of a dolasetron and EMEND combination.
CHAIRPERSON
CAMILLERI: Yes. I was also requesting further studies with
dolasetron. My overall reason to say yes
was that I was quite **persuaded by the information that the metabolism of
dolasetron was unlikely to be very dramatically altered in this context. But I think further studies would be very
useful.
Other
comments?
(No
response.)
CHAIRPERSON
CAMILLERI: Okay. Can we move on to question number 4? This is a long one. Aprepitant is an inhibitor of the CYP3A4
metabolic pathway. For chemotherapeutic
drugs that are metabolized by this pathway, moderate inhibition of their
metabolism could result in serious or life‑threatening toxicity.
So
the first thing we are going to do is we are going to address the issue
pertaining to 4A. The applicant has
analyzed the safety data by chemotherapy regimen. And a significant number of patients received
etoposide, vinorelbine, or paclitaxel, all of which are substrates for CYP3A4,
in combination with cisplatin and the aprepitant regimen.
Here
are the questions. Is this data
sufficient to support the safety of aprepitant in combination with these
specific drugs; that is, etoposide, vinorelbine, and paclitaxel?
Would
anybody like any questions answered or can we go ahead and address and answer
the question?
(No
response.)
CHAIRPERSON
CAMILLERI: I see no lights coming
on. So I think this will probably be the
easier part of the question. So we want
to know is there sufficient data to support the safety of aprepitant in
combination with the drugs etoposide, vinorelbine, and paclitaxel? This time we will start with Ms. Hoffman.
MS.
HOFFMAN: There was a comment about
sepsis being three times as high with the vinorelbine. Can you just discuss that briefly again?
CHAIRPERSON
CAMILLERI: Dr. Proschan, I believe you
sort of addressed that question slightly by saying there are multiple comparisons
being done here and you felt that the signal here was relatively small
considering the very small number of instances.
DR.
PROSCHAN: Right. And that's why I think it is impossible from
this data to say, "Okay. It is
harmful." Likewise, I think it is
impossible to rule out harm.
So
to me, there hasn't been sufficient data to establish safety, but it might be
very hard to have sufficient data to establish to a high degree of certainty
that it is safe.
CHAIRPERSON
CAMILLERI: Dr. Della'Zanna, do you have
any other comments?
DR.
DELLA'ZANNA: That was exactly what I was
trying to get across. I wasn't trying to
say that this should not be used in conjunction with vinorelbine. I was trying to suggest that this might
represent a small signal that we could not define. One of my concerns was some of these
respiratory serious adverse events as well as the incidence of infections.
Like
I said, ‑‑ and I will emphasize it again ‑‑ the numbers
are very small. However, the numbers
that were serious infection‑related adverse events were only seen in the
aprepitant group. So that was what I was
trying to focus on.
And
from that, I wasn't necessarily looking for condemning the use with
vinorelbine, just the committee's opinion on whether additional information is
necessary.
DR.
PROSCHAN: Wasn't it also the case that
several of those events were at the same site, same ‑‑
DR.
DELLA'ZANNA: The significance of that is
uncertain for me only because this one site focused predominantly on lung cancers. So the fact that these all occurred in one
site does not surprise me that this site focused and is concentrated in lung
cancer.
The
firm stated that it was balanced between the two treatment groups at the number
of patients with these primary lung cancers.
It wasn't biased.
CHAIRPERSON
CAMILLERI: Dr. Kelsen?
DR.
KELSEN: I think we have all indicated
that it works to decrease nausea and vomiting.
So it is effective in that setting.
I have a question for the agency because I think this is where ‑‑
you know, I am just a visitor to this.
But as an oncologist, is there a precedent for using an agent like this
in which one feels pressed into indicating exactly which drugs it can be given
with, as opposed to it's recommended for highly emetogenic chemotherapy, as
represented by cisplatin, because we are now facing a situation where you are
going to try to tailor the specific combination regimens, not only class by
class but almost drug by drug, on the basis of not much data?
Has
this ever come up to you all before? Is
there anything to guide us?
DR.
HOUN: Well, it frequently comes up
because when drugs are tested and to be used with other drugs, what are these
other drugs? How do you label? And so the reason why we are airing this is
because we want the public to know that we have discussed this.
So
when the agency gets criticized that you didn't look carefully that they only
had enough patients in these three drugs, why are you giving it broad labeling
for everything, we want to say, "Well, you know, we are aware of those
issues. And we brought it to the
public's attention. We have had a
discussion about it."
So
that is why it is here. It is not our
desire necessarily to state specifically which of these drugs, but those were
the ones that had a lot of patients. And
there will be other drugs that didn't.
How do you guys help us with advice on handling that?
DR.
KELSEN: I would like to make just one
other point, that these are all intravenous drugs. I was struck by the comment that it may be
oral agents that become an issue. We are
working very, very hard to switch to oral chemotherapy. There are a number of models of that. I don't think this is a trivial issue at all.
DR.
DELLA'ZANNA: The other think I would
like to bring up ‑‑ and I realize that the inhibitory effect is
greatest on the oral. We seem to play
down the fact that the IV methylprednisolone had a 35 percent increase.
The
tables that were demonstrated on the slides were somewhat misleading, as far as
I'm concerned, when you considered the dexamethasone dose and the divergence of
the two lines were generous. Then when
they showed the methylprednisolone IV, you can almost superimpose them, even
though there was a 35 percent difference.
And
if you want to pull up your slide that I am talking about, I have it here. Where is it?
We can just keep going forward, though.
CHAIRPERSON
CAMILLERI: Ms. Hoffman, do you have
another question? Yes, Dr. Levine?
DR.
LEVINE: Just we shouldn't jump ahead to
the next sentence, but I would like to know whether pre‑approval or post‑approval,
what kind of time frame would it be to get satisfactory numbers and data for
either pre or post‑approval regarding the issue we are talking about from
the agency?
DR.
JUSTICE: I think we discussed the
wording of this question to some extent.
I think in terms of pre‑approval, we are talking we could deal
with that in labeling if we thought there was a potential drug‑drug
interaction that was significant enough that the drug should not be used in
combination with another drug. We could
address that in labeling and until a study was done to document that there is
or is not a drug interaction.
So
I don't think we are asking whether an actual study would have to be done pre‑approval. So our question is a little bit misleading.
DR.
LEVINE: Thank you,
CHAIRPERSON
CAMILLERI: Maybe I could ask Dr.
Della'Zanna whether there would be any advantage in splitting up this trial of
drugs. It seems to me that you had very
little concern about the combination with etoposide and paclitaxel. And, yet, from the response to Ms. Hoffman's
question, there still are some reservations with regard to vinorelbine in
combination.
DR.
DELLA'ZANNA: The most significant thing
that I noticed on the vinorelbine was the pulmonary insufficiency that was
ultimately fatal and then that you included an additional two fatalities that
were serious infection‑related.
And then in the corresponding standard therapy group, there were only
two fatalities, neither of which were related to truly a pulmonary problem
other than a pulmonary emboli and a death that was reported as unknown.
CHAIRPERSON
CAMILLERI: But I remember that we got
some information that the vinorelbine toxicity appeared not to be related to
the usual bronchospasm and acute syndrome but appeared more related to the
underlying lung disease.
Thirty
seconds.
DR.
REINES: Okay. If I could have slide 755, please? I really want to echo the comment that when
we pull things apart in different ways, the results aren't always
balanced. We pre‑specified the
AEs, as I told you in my main talk, that were indicative of chemotherapy‑induced
toxicity.
These
are the data for vinorelbine. The pre‑specified
AE incidences were the same for both groups.
The infections were higher, as we have been discussing, in this group.
If
you look at hematological AEs, it goes in the other direction, which you
haven't been shown yet. But that is how
the numbers come out overall the same.
So
we have looked very carefully at this.
We did think that the respiratory issue was not a vinorelbine type of
toxicity. And we looked very carefully
at the hematological toxicity with this drug.
There is no evidence that aprepitant is enhancing that toxicity.
CHAIRPERSON
CAMILLERI: Thank you.
Dr.
Levine?
DR.
LEVINE: Just in reference to another
large study that is just developing post‑marking on an approved drug, was
there any evidence on pulmonary function tests that were done in these
patients, either before or after death?
And was there a diffusion defect or pulmonary hypertension that
developed in these patients due to drug?
DR.
REINES: No.
DR.
LEVINE: It was done or not done,
pulmonary function tests?
DR.
REINES: We don't have that
information. It was not done as far as I
know.
DR.
BRAWLEY: Quick question for a
statistician. Are we technically doing
the subset analysis here? And
substantive analysis is inherently flawed and likely to give you the wrong
answer.
DR.
PROSCHAN: Right. I mean, that's why I said earlier if you try
and attach a statistical significance to this, it is going to be very difficult
because you are looking at so many different drugs, so many different outcomes.
We
have been focusing on the ones in which you see some trend. But even in the ones in which there is no
trend, where it looks dead even, there still could be harm that you just can't
see with this number of patients.
So
if you really want to prove that there is no interaction with any of these
drugs, it is going to take thousands of patients to do that.
DR.
BRAWLEY: That brings us back to Dr.
Della'Zanna's original comment, which is that we should be cautious because
these are all small numbers and small trends that may mean nothing, may mean
something.
CHAIRPERSON
CAMILLERI: Okay. I believe we have had sufficient
discussion. Any other clarifications
needed on this specific point?
(No
response.)
CHAIRPERSON
CAMILLERI: Dr. Proschan, I am going to
start asking you to vote this time again.
The question, therefore, is, are the data sufficient to support the
safety of aprepitant in combination with the drugs etoposide, vinorelbine, and
paclitaxel?
DR.
PROSCHAN: I don't think they are, but I
think it would take thousands to make it so.
CHAIRPERSON
CAMILLERI: I am assuming that Dr.
Proschan's answer is no.
DR.
PROSCHAN: As stated, to this question as
stated, I would have to say no.
CHAIRPERSON
CAMILLERI: Dr. Desta?
DR.
DESTA: I'm not sure.
CHAIRPERSON
CAMILLERI: This is the time to come off
the fence, Dr. Desta.
(Laughter.)
CHAIRPERSON
CAMILLERI: You could abstain. Sorry.
I thank you.
DR.
DESTA: Because the question is "Is
this data sufficient to support?" it is "Yes" or
"No." And we don't know. I don't know.
CHAIRPERSON
CAMILLERI: I am assuming that is an
abstention, then. Dr. McLeod?
DR.
McLEOD: McLeod. Taking all three drugs together, which is the
way the question is posed, I would say yes.
DR.
BRAWLEY: Brawley. I'm very much on that fence, but I'm leaning
over into the yes. So I'll go yes.
DR.
KELSEN: I'll say yes. And they will need those additional studies.
CHAIRPERSON
CAMILLERI: That was Dr. Kelsen.
DR.
LaMONT: No. The data is insufficient. LaMont.
DR.
LEVINE: I'm uncomfortable with it, but I
will say yes. From these other
experiences with post‑marketing, as all of you are saying, these are very
serious consequences. Therefore, I am
looking forward to the next sentence, but I would say yes.
CHAIRPERSON
CAMILLERI: That was Dr. Levine. Now Dr. Metz.
DR.
METZ: I'm going to say yes within the
limitations that this is designed in such a way that you actually cannot answer
the question because there are not enough patients. But what I would like to see is post‑marketing
data. I think that is very
important. I don't want the fact that
this may ultimately be an issue to limit the availability of this agent. So that is why I am voting yes.
CHAIRPERSON
CAMILLERI: Camilleri. Yes with additional studies post‑marketing.
DR.
CRYER: Cryer. Yes with additional studies as well.
DR.
FOGEL: Fogel. Yes with additional post‑marketing
studies.
MS.
COHEN: Cohen. No because can you tailor a regimen? What kind of advertising is there going to
be? Was this oral versus the IV? There is just not enough data.
Post‑marketing,
what happens to us who get caught before the post‑marketing if it's
used? I think it is too chancy.
MS.
HOFFMAN: Hoffman. Yes with post‑marketing studies.
CHAIRPERSON
CAMILLERI: Thank you.
So
I think we have kind of answered what additional studies are going to be
needed. Do we need to address it any
further? Does the agency want us to
specify what sort of post‑marketing or other studies?
DR.
HOUN: I think if people do want to give
suggestions on endpoints, that would be helpful.
CHAIRPERSON
CAMILLERI: Thank you.
Dr.
Metz?
DR.
METZ: If I may comment, it is not so
much what the endpoint is and it is not so much on what the design of the study
is going to be. What I think is
important is you have to realize that any drug that is ever going to be
marketed for a specific indication ultimately is only going to be studied in so
many patients. We will have to learn as
time goes on.
They
will certainly be patients who get this drug or any other drug at any time with
a life‑threatening cancer illness who may get sick. And the signals are hard to find. You people are the experts on post‑marketing
surveillance problems and also on the fact that there's no really good way to
fix it, which brings us back to all the other previous discussions we have had
in this committee.
I
think it is important to just realize that this is a possibility and that
patients will get as good care as they can from the individual doctors and that
as data accumulates, information will be acquired.
CHAIRPERSON
CAMILLERI: Yes. Dr. Kelsen?
DR.
KELSEN: I am going to make a suggestion
sort of to us at ODAC. One way to
address the survival issue, which we were not able to address, is to recommend
that when future studies are done in lung cancer, that they specific the
antiemetic regimen very rigidly so that all patients not only get the same
chemotherapeutic regime, they get the same EMEND or whatever this is
regimen. And then you will have an
answer as to whether there is an effect on survival.
We
will not be able to address safety because I think both arms will get the same
thing. But you will know what the
survival outcome is.
CHAIRPERSON
CAMILLERI: Dr. LaMont?
DR.
LaMONT: Yes. I wonder if we could learn anything from the
times of exclusions that were used in the clinical studies because, as someone
has already mentioned, this is going to be opened up to all kinds of cancer
patients with all kinds of backgrounds.
So
I assume that the patients who had had previous infection or recent infection
or fever, et cetera, et cetera, leukopenia, neutropenia were excluded. Perhaps we can build some of those safeguards
into the indications and post‑marketing surveillance.
CHAIRPERSON
CAMILLERI: Thank you.
Dr.
Horgan?
DR.
HORGAN: The enrollment criteria were
quite broad. And we obviously wanted to
exclude anybody with an active serious infection. We had exclusions for low neutrophil counts
and abnormal white cell counts and renal function and liver function that would
be consistent with what the normal criteria for the administration of
chemotherapy were.
In
general, we excluded patients who are receiving potent inhibitors of CYP3A4 and
inducers of CYP3A4, but apart from that, the exclusion criteria were very
similar to what have been used in previous antiemetic trials to allow a
population that was as representative as possible to clinical practice to be
studied.
CHAIRPERSON
CAMILLERI: Dr. McLeod?
DR.
McLEOD: I think as we get into Part B of
this question, it will come out even further.
But as far as suggested studies, most of the concerns that have been
raised so far have been of a pharmacokinetic nature.
Now,
whether it starts with pharmacodynamic variability is to be seen, but certainly
there could be some very defined minimum studies where the presence of a
pharmacokinetic interaction is evaluated.
These
studies do not have to be done fairly quickly, but if there is no
pharmacokinetic interaction clear from even single‑dose combination
studies with this agent and the chemotherapy drug, that will give us some
further confidence on its use.
It
would not be enough to declare that it is safe for all mankind, but in the
context of Dr. Metz's comments, we are not robots. This is not computer circuitry and
engineering. There are some studies that
have to be done and learning that has to go on that is beyond the scope of the
FDA.
CHAIRPERSON
CAMILLERI: Dr. Kelsen?
DR.
KELSEN: Just one last comment to follow
that up. You could imagine a study where
women with breast cancer commonly receive single‑agent vinorelbine. It's not very emetogenic, but you could
easily do a small trial with this agent.
And with single‑agent vinorelbine, you would get your answer in 15‑20
women.
CHAIRPERSON
CAMILLERI: I'm assuming somebody would
want to know about pulmonary function, transfer factors, and all the other
things related to vinorelbine, peak flow rates, capacity, et cetera, to at
least start to address that question in the context of the pharmacokinetic
study as well.
I
believe we can move on to question 4B, few or no patients received docetaxel,
vinblastine, vincristine, ifosfamide, irinotecan, or imatinib, which are all
substrates for CYP3A4, in combination with the cisplatin and the aprepitant
regimen. The docetaxel drug‑drug
interaction study has accrued only five patients. We have seen the data.
So
the question is, is there sufficient data to support the safety of aprepitant
in combination with these drugs? Does
anybody want further discussion before we take a vote on this? Dr. Metz?
DR.
METZ: Yes. I'm sorry to harp on the same point
today. I don't know actually if there is
any real difference if you say five people have had docetaxel, nobody has had
vinblastine, and a whole number but not enough have had vinorelbine.
So
I think it is the same question. I think
you are really asking us the same question.
In the subgroup that wasn't big enough, well, here is a subgroup that is
even smaller. It is going to be the same
kind of response that I would have to make.
So
no. But the only way we are going to
find out is by testing enough patients.
CHAIRPERSON
CAMILLERI: We have a quick, enlightening
question. Dr. Levine can tell us in the
meantime this question.
DR.
LEVINE: It would just seem to me from
the former answer that we had on pharmacokinetics I would feel reassured with a
pharmacokinetic study for all of these pre‑approval.
CHAIRPERSON
CAMILLERI: Let's have some further
insights. Good.
DR.
ROWLAND: Yes. I was reflecting on the question that I was
asked this morning.
CHAIRPERSON
CAMILLERI: Can you introduce yourself,
sir?
DR.
ROWLAND: I was reflecting on the answer
that ‑‑
CHAIRPERSON
CAMILLERI: Who are you?
DR.
ROWLAND: Sorry. My name is Malcolm Rowland.
I
was asked the question before about the docetaxel study. And I was reflecting on it over lunch and
asked the company if they would have data available to bring up a number of
points. If I could have slide 1113? Can I have that? Because I think there are several things that
are going around. And I think we may not
have as clear a picture.
The
point I was making before was that, in fact, in answer to the docetaxel issue
is that this is an intravenously administered drug. The interaction we are looking at is whether
intravenously drugs are affected.
There
are three or four substrates that are affected.
This is the group of drugs over here that we are talking about that was
actually done. So we have already talked
about methylprednisolone, ondansetron, erythromycin, and docetaxel. Docetaxel, it is inferred that that may not
be representative.
I
am a little worried about that because the FDA has and many people have
advocated the use of enzymology and an understanding of that enzymology in
order to make some statements about how we think some things are happening so
that we don't have to study every drug X that comes along but we use sound
scientific principles.
Docetaxel,
to my knowledge, has been one which has been correlated with what is known as
ear, throat, mouth and breath test, which is used as a test for the systemic
activity of 3A4 and has been correlated with midazolam. So to say that this is not representative of
3A4 doesn't make sense to me. You may
want to think about that.
I
think the other thing is, as I said, there is very little effect on
intravenously administered 3A4 substrates.
Where we see the effect more ‑‑ and I think it was pointed
out that they are moderate ‑‑ is to drugs where the drugs are given
orally. And that is because it occurs in
the *response of the drug at the interstinal level. And so we see it there. These were the magnitudes that were discussed
this morning. So I want to indicate to
you that the route of administration is very important.
Another
thing that was suggested was this issue of polymorphism. To my knowledge, there is no polymorphism in
CYP3A4. It is a unimodal dispersion in
the population. We know very little
about what correlates with that variability.
I know of no diagnostic that would predict the CYP3A4 activity other
than giving the drug and looking at what is going to happen. So we don't have polymorphism, but we do have
variability.
So
if I can relate this back to a slide which was done, 36, if I can have that,
which was the thing that was striking me, ‑‑ this is 36 ‑‑
and we are talking about this drug being in this thing, which is moderate, the
same or very similar to grapefruit juice, verapamil, and diltiazem, then it
seems to me that if there is a question of concern about this drug, then
presumably there is a question of concern about these other drugs, too,
because, as far as I can see, I can't tell the difference. If you just gave me the data and didn't tell
me the drug, I wouldn't know the difference.
So those are my comments.
CHAIRPERSON
CAMILLERI: Thank you. I guess the other drugs and grapefruit juice
are not up for discussion today.
DR.
ROWLAND: All right. I appreciate that.
CHAIRPERSON
CAMILLERI: Dr. Della'Zanna?
DR.
DELLA'ZANNA: I have two points I want to
bring up. Okay? First of all, the other drugs that you were
talking about do not have the same narrow therapeutic index. The effect that we saw with IV
methylprednisolone was a 35 percent increase in area under the curve. Okay?
Now,
that still might be labeled for you as a small increase, but if you increase
the plasma levels of some of these cytotoxic agents by 35 percent, you might be
breaching into a toxic level.
DR.
ROWLAND: Can I just respond? I mean, I think there are two aspects. One is the magnitude of change that occurs
when you bring drugs together. And the
other one is the therapeutic implication of a degree of change.
I
think one thing that is very clear about 3A4, it's highly variable. If I give a drug, a standard dose, to anyone,
I have no knowledge of what that variability is going to be. So people who are getting standard doses are
getting a four to five‑fold variability and exposure full stop, before we
even start.
And
we live somehow. Somebody lives with
that. I mean, presumably it's clinical
management. Maybe one day we will have
diagnostics associated with that.
DR.
HOUN: You expressed our responsibility
in terms of FDA's public health responsibility and the difficulty of it very
well.
DR.
ROWLAND: I appreciate that. We are all looking for the diagnostic, the
prognostic that would predict the handling in individuals.
CHAIRPERSON
CAMILLERI: Thank you for your
intervention.
Yes,
Dr. Cryer?
DR.
CRYER: I just wanted to follow up on a
comment that you were making, Dr. Della'Zanna, with respect to the
corticosteroid‑related increases in serum concentration. So in the clinical studies that were done, as
I understand it, the dexamethasone dose on subsequent days was reduced to
provide plasma concentrations that were similar to control.
So
the question, the specific question, I have in that regard is, is it proposed
for the label that the dexamethasone dose would similarly be reduced in
subsequent days' doses with the aprepitant‑antiemetic combination?
DR.
DELLA'ZANNA: Yes. The dexamethasone dose was decreased not only
for subsequent days but also on day one.
My concern is we saw that interaction, resulted in decreasing the
regimen by 50 percent, but we haven't applied or even really analyzed whether
that same interaction is going to occur with cytotoxic agents.
There
are no recommendations mentioned in the label saying that if you're on
vinorelbine, decrease your dose by 50 percent.
It's not there because we don't know.
It hasn't been evaluated. That is
my concern for this.
If
we saw these kind of effects in dexamethasone and the effect was enough to
decrease and change the regimen but we haven't looked in the cytotoxic agents,
realizing that yes, the inhibitory effect is much more on oral drugs, we can't
ignore the fact that the IV methylprednisolone resulted in a 35 percent
increase.
DR.
CRYER: You raised an important point
that I actually had forgotten. That was
a point that struck me earlier, which was that the effect of aprepitant on the
potential to raise plasma levels of chemotherapeutic agents was, as you rightly
pointed out, has only been done with aprepitant alone, rather than the combined
antiemetic combination, which will actually be suggested for use in clinical
practice.
And
so that would definitely be an area for studies that would need to be looked
at. And that would be the effect, I
think, with the combined antiemetic therapy, for which we have no data on at
all, as I understand it.
DR.
ERB: But we have clinical data on it.
DR.
REINES: Yes. The point that we wanted to make was that
that is what our clinical safety data reflect.
That is what we are asking you to consider. All of those clinical data, of course, in
Phase III were with the regimen, not with aprepitant alone. And so our safety argument is the argument
for the regimen.
CHAIRPERSON
CAMILLERI: Dr. Fogel?
DR.
FOGEL: I have a question for the
agency. Given the dynamic nature of
chemotherapy and given, as has already been alluded to, we are going to be
moving from intravenous to oral medications, hopefully there will be lots of
new and more effective medications coming to market in the course of the next
few years, what is the agency's thoughts about sort of how drugs are approved?
Is
the agency believing that to avoid criticism, these approvals should be very
narrow so that you can only use certain combinations or does the agency believe
that there should be a certain amount of openness in the approvals with
extensive post‑marketing data collection?
DR.
HOUN: I think that's a difficult
question. I think it will depend on the
specific drug alternatives, the indication.
And if you have a new drug for a life‑threatening indication, no
alternatives, what amount of safety data you have may be less than if you had a
me, too, fifth‑of‑a‑kind that you are trying to bring to the
market as a new molecular entity.
I
am thinking that because these are difficult questions and because the public
should not, as our consumer representative, patient representative said, be
blind‑sided, that this is a public discussion, it's for the record, it's
on the internet, that issues be publicly vetted so that we can hear what the
experts are saying, there is a chance for the company to respond as well as
public input because these are difficult questions. These are policy questions. There is not a right or wrong. It's judgment.
DR.
FOGEL: The reality is that you are
probably going to be second‑guessed, no matter what happens. If this is a safe drug, you are going to be
criticized for not having a broad use.
And if it turns out that, unfortunately, somebody has a serious adverse
side effect that kills them, you are going to be criticized for being too
liberal. You can't make a decision based
on the data that we have.
We
are all stuck by this. And I think that
by having these discussions and sort of having the label written with this
ambivalence put in where it's clear that the data is not available for a
broader use would be very helpful. And I
think it would help direct physicians.
CHAIRPERSON
CAMILLERI: Thank you, Dr. Fogel.
Other
questions or clarifications required on this point?
(No
response.)
CHAIRPERSON
CAMILLERI: If not, I want to remind you
of the question that we are asked to try to answer. The question is very specific, is there
sufficient data to support the safety of aprepitant in combination with the
drugs docetaxel, vinblastine, vincristine, ifosfamide, irinotecan,
imatinib? Dr. Proschan?
DR.
PROSCHAN: I think the answer is no as
written here.
DR.
DESTA: No as written here.
CHAIRPERSON
CAMILLERI: That was Dr. Desta.
DR.
McLEOD: McLeod. No with specific post‑approval or pre‑approval
if deemed necessary studies.
DR.
BRAWLEY: Brawley. No.
DR.
KELSEN: Kelsen. No.
DR.
LaMONT: LaMont. No.
DR.
LEVINE: Levine. No.
DR.
METZ: Metz. No with a request for post‑marketing
studies and specific concerns relating to future oral chemotherapeutics.
CHAIRPERSON
CAMILLERI: Camilleri. No.
DR.
CRYER: Cryer. No.
DR.
FOGEL: Fogel. No.
And I think that small studies actually aren't going to help you very
much. It is only when there is
widespread use of a drug that you are actually going to get the answers that
you need.
MS.
COHEN: No. And I hope I don't have to give an answer to
it.
MS.
HOFFMAN: Hoffman. No.
CHAIRPERSON
CAMILLERI: Thank you.
Do
you require any further clarification on the types that would be useful to
address 4B?
DR.
HOUN: Yes. I think we should have some discussion. Everybody voted no. There has been a proposal that this be
handled strongly in labeling so that this ambivalence on we don't have
information be placed in the label.
My
interpretation means that you are interested in studies post‑marketing. I just want to confirm that. Are there people who are saying some of these
studies should hold up the approval for the drug?
CHAIRPERSON
CAMILLERI: Ms. Cohen seems to have an
answer.
MS.
COHEN: Well, as you can gather by now, I
spent part of my life in consumer protection.
And part of my expertise is in advertising. I see advertising for pharmaceuticals that
FDC and FDA is finally recognizing is deceptive. I am looking at one of the proposals for a
package insert. If that is plain
language, then it is certainly not English that I understand.
I
am concerned that you don't have enough studies. People are not getting the care that they
need nowadays. Doctors don't have time
to speak to them. They become a little
cavalier.
And
I don't think people should have to say post‑marketing, "If someone
dies, then we have learned something."
Why can't we learn something before they die? I think it is very cavalier.
The
practice of medicine today has changed dramatically. I am boring some of you. I am looking at your faces. But when it hits a member of your family,
then you care. And I am here to see that
consumers get the attention they need and they are not getting anymore.
There
is just not enough evidence. When I hear
about sepsis and toxicity, oral versus IV, there are so many adverse
events. Just making notes, drug‑drug
reaction, drug reaction to the drug, I am sitting here. Is this safe and effective? What are we here for? It is not the bottom line.
I
own Merck stock. But, believe me, I
would rather take less money for it and know that my consumers are going to be
protected. This is a tough world, and we
have to help people.
I
am sorry if I am giving you this speech, but you can see I am upset. I am worried.
What is the next generation going to do?
CHAIRPERSON
CAMILLERI: Thank you.
Can
I ask Dr. McLeod to specify what pre‑approval studies he would
recommend? Did I understand you
correctly?
DR.
McLEOD: Well, I didn't know whether to
define whether it needs to be pre‑approval or not because I haven't had
time to think through the implications of that.
One
thing I was just doing right now because of Ms. Cohen's comments was looking
through the drugs that were commonly co‑administered with this agent as a
place to start because, I mean, all anti‑cancer drugs are possibilities
to be combined with cisplatin and this antiemetic regimen, but there are
certain players that are going to be very common, such as the ones there.
So,
for example, the docetaxel study that is ongoing now is recognized by everyone,
including the applicant, that that is an issue, that cisplatin, docetaxel is
going to be a common combination in which this drug will be added. So they are already on their way with that
study. And that needs to be expedited. I think that needs to be done pre‑approval
because of its importance in establishing one way or the other what it is going
to mean.
DR.
HOUN: Could the company please just give
us the time line on the completion of that study?
DR.
GOTTESNER: We have been working on that
study for over two years. We are
accumulating patients on the average of about one every two to three
months. That is despite the fact that we
have looked at sites throughout the whole world in order to find such patients.
It
is not easy to do these studies. I just
want to make it very clear.
CHAIRPERSON
CAMILLERI: I saw Dr. Kelsen's eyebrows
move.
DR.
KELSEN: What's the design of the
trial? I got the PK part of it.
DR.
EGORIN: My name's Merrill Egorin. I am serving as a consultant to Merck. University of Pittsburgh was one of the sites
chosen to try and get this study done.
It
was a very simple drug‑drug interaction study, patients getting single‑agent
docetaxel with aprepitant as the antiemetic.
There was really no incentive for patients to be hospitalized overnight
in the GCRC unit.
We
tried to get informed consent. We got no
patients to sign up for two years. And
that was despite taking a fair amount of time sitting and talking with
patients.
I
also, as long as I am up here, think it is fair to say that just because we
went to medical school doesn't mean that people in our family haven't had a
malignancy. So I think that is an
important thing for consumers to understand.
The
other thins is it is sort of an oxymoron.
If you have a drug that orally makes you throw up a lot, you are not
going to give it to patients. So the
orally administered drugs that are coming forward are not highly emetogenic
because if they were, you would never be able to give them to anybody.
DR.
KELSEN: I was referring to the ones that
are going to be given with cisplatin.
Those studies are with platinum.
They are all being written, and they are all underway.
DR.
EGORIN: The reality is if you are
looking at approved drugs, we could not get patients with no real benefit to
agree to spend two nights in a GCRC away from their families. It is a very, very hard sell.
DR.
HOUN: So, Dr. McLeod, I just wanted you
to see when you say "pre‑approval," there are some
difficulties.
DR.
McLEOD: Well, I think this speaks to the
need for a change in stage design, rather than a lack of need for the
data. Within the cooperative groups, we
do studies where we do limited sampling.
And it is very slow. We all
complain about how slow it is going, but it is not that slow.
I
think the study design is probably fantastic and so thorough that we can't get
people in. I mean, for this sort of
study, when we do an institutional study of this sort, we would not be putting
patients inpatient. We would be
sampling, doing the sampling, in the outpatient facility.
Maybe
it is not rigorous enough for what you require.
I don't know the answer to that because certainly we are not submitting
our data as part of an FDA application.
And so it may be that the rigor is just obstructive to be able to do the
study.
I
think the issue is still there. I can't
remember the wording Ms. Cohen used, but we either have to just throw it out
there and see what happens, which is paraphrasing a bit, or try to do these
studies.
If
it is impossible to do these studies, this drug in my view ‑‑ I
guess I will be on the record saying this ‑‑ looks to be an
important advance. I would not want this
drug held up for this issue, but Ms. Cohen's point as well as Dr. Egorin's,
patients out there, if they are harmed, one will be too many.
CHAIRPERSON
CAMILLERI: Dr. Cryer?
DR.
CRYER: Right. So, as I remember, I think Ms. Cohen's
terminology was "cavalier."
Actually, listening to the sponsor, I think that there has been an
earnest effort to acquire these patients with these specific combinations.
Your
question, Dr. Houn, was, is it our opinion that the approval should be held up
for these additional studies which we are recommending? From my personal perspective, having heard
the arguments, I would say the answer would be no primarily because of the
advancement that this drug represents compared to the difficulty of acquiring
patients in the clinical trial experience.
However,
I would like to make what I consider to be an important comment with respect to
the post‑marketing acquisition of data.
And that is that we just don't know what the adverse event profile is
going to be with these drugs in combinations with specific chemotherapeutic
agents. And in the Phase IV experience,
we are going to be dependent upon spontaneous reporting of physicians.
Education,
physician education, I think is going to be integral, going to be key to that
mechanism. The label is really going to
be the only tool or one of the best tools that you have for educating
physicians to appropriately alert us as to these potential interactions.
And
so with respect to the specific wording in the label, I did want to bring the
discussion to a precautionary section that was in Dr. Della'Zanna's slides, in
which it says, "EMEND should be used with caution in patients receiving
concomitant medicinal products that are metabolized through CYP3A4. Some chemotherapy agents are metabolized by
CYP3A4."
I
am not so certain that physicians will know in the walking inventory what those
chemotherapeutic agents are that are metabolized via that pathway. And if reporting in the post‑marketing
experience is going to be important and improve the analysis of this product, I
also then would think it would be important to specifically state in the label
in that precautionary statement what those chemotherapeutic agents metabolized
through that pathway might be.
CHAIRPERSON
CAMILLERI: Thank you, Dr. Cryer.
Dr.
Metz?
DR.
METZ: Yes. I think we are all grappling with the same
problem and taking it around and round in circles. To put it into perspective, I think there is
a certain defined 20 percent benefit that we are all very, very comfortable
with here and was not an issue for any of us.
We
now are getting concerned about a theoretical concern that actually cannot be
asked before release. And I think the
point is you need to see lots of patients with lots of experience.
Therefore,
I would second what has just been said by Dr. Cryer. The label has to say that the testing was
done with this particular agent and have had so many patients in and wasn't
done with this particular agent and it was done with this particular agent, but
it was so few patients. That is the
database, which is growing as time goes on.
So
you are absolutely correct to raise the concern. I would hate to see the patients who are
clearly going to benefit from an important advance limited because of theoretic
worries we have about where we want to come down on our votes.
CHAIRPERSON
CAMILLERI: And I think, Dr. McLeod, you
actually specified at the very end the same philosophy ‑‑
DR.
McLEOD: That is correct.
CHAIRPERSON
CAMILLERI: ‑‑ that this
medication should move ahead.
DR.
McLEOD: I totally agree. That is not the point I wanted to make with
this, but I will reiterate that. I mean,
I would love to see those PK studies but not at the expense of slowing down
this drug out there.
There
may be some patients that end up having some adverse events that weren't
predicted. We know that there are going
to be patients, a lot of patients, benefitting from this.
The
point I wanted to make was if you look at this list of drugs that we were just
voting on, only one of them is an oral agent.
And that oral agent is not highly emetogenic and also has quite a lot of
variability already in its blood levels.
That's the imatinib.
So
of those agents we are voting on, it is not a big issue. Now, worrying about the future, certainly
that is something that has been raised.
But I just wanted to point out for those of you who are not familiar
with these agents that only one of them is currently oral. And it is not likely to be a big issue in
terms of interaction here.
CHAIRPERSON
CAMILLERI: Thank you.
Dr.
Brawley?
DR.
BRAWLEY: First, I agree with what Dr.
Cryer and Dr. Metz said wholeheartedly.
And that was part of my comment.
I want to speak partially to the consumer community. I see a lot of patients who vomit an awful
lot. Even with the drugs that we
currently have, they vomit an awful lot.
And they need something better. I
see here something that sounds like it's better.
Now,
we may not have 100 percent assurance that it is absolutely safe at this point,
but scientifically to find out that it is 100 percent safe with all of these
drug combinations is actually probably impossible.
If
you went to the old Soviet Union and dictated that everybody go onto a clinical
trial and run a clinical trial of 100,000 cancer patients for 5 years, you are
not going to find all the ins and outs, all of the nuances of this drug in
combination with other drugs.
I think we have to realize that every drug
that is approved has some risk associated with it. I think all of us have seen people die from
aspirin.
Thank
you.
CHAIRPERSON
CAMILLERI: Thank you.
Ms.
Hoffman?
MS.
HOFFMAN: Yes. As a parent whose child went through BMT pre‑5‑HT3
therapy, et al., in 1987, it was
hell. I do want to say, too, that I
don't want to see this drug stopped. I
think there is great value to it. It was
horrendous. We are talking vomiting
every five minutes day in, day out 24 hours a day.
That
said, I do want to see some post‑marketing studies done. And I would like to know what steps are being
taken? Now that you have done a Phase
III trial in adults, what is happening in terms of pediatrics? Are there tests and studies planned? Where are you in that process?
You
talked about patient population. We have
got COG. And kids are pretty much in‑hospital
and a cooperative group. So there is a
patient population there.
CHAIRPERSON
CAMILLERI: Thanks.
Can
we have a very brief comment on what other studies are being done in
particularly children with cancer?
DR.
HORGAN: As we mentioned, this is
something that has been actively concerning us.
That is why we enrolled a few patients at a specific site in our Phase
III program where they had access to a pediatric population. They were very eager to see how the drug
would benefit their patients.
We
are actively considering pediatric studies with a view to doing a study in
adolescent patients initially to assess the efficacy in an adolescent
**population getting highly emetogenic chemotherapy.
CHAIRPERSON
CAMILLERI: Thank you.
Dr.
Fogel?
DR.
FOGEL: I agree with Dr. Brawley's
comments regarding the importance of this new drug and the fact that we cannot
know with absolute certainly about its safety.
I also agree with what he said, that the drug should be released in
these post‑marketing studies, can be obtained obviously after the drug
has been released.
There
is just one concern I have. When a new
drub comes to market, particularly one that has been shown to be effective,
doctors will tend to generalize and expand the indications. You may find that there are doctors who will
use this for nausea and vomiting that is not chemotherapy‑related.
I
make a strong urge to the agency to make sure that this possibility is excluded
by specific wording that this drug is only approved for chemotherapy‑induced
nausea and vomiting.
DR.
HOUN: What is the GI experts' view on
the potential for off‑label use for nausea and vomiting for a variety of
GI conditions? Is there anticipation?
DR.
LEVINE: Yes. Levine.
I
would say definitely yes. And I would
say this is the time on the labeling to put it in bold. The only thing a general practitioner looks
at is the bold print usually. And if he
is lucky enough to look at that, it must be a small percentage.
I
would put something like this in bold print, exactly what we have
discussed. I would agree with the post‑approval
with kinetic studies, pharmacokinetic studies, also.
CHAIRPERSON
CAMILLERI: Dr. Metz?
DR.
METZ: Yes. I would like to actually support that. And I would agree entirely with Dr.
Fogel. Off‑label use might be the
dangerous situation here. Treating for
more than five days might be an issue because of this auto‑metabolism and
a few other things that were mentioned earlier.
Also,
I think we jumped to assume that rescue therapy is ‑‑ this drug
cannot be used for rescue therapy.
That's treating somebody for nausea.
I would make sure the label has that this is a prophylactic regimen that
is going to be used. It works, and it's
safe. There are a lot of problems in
terms of patients who are vomiting. It
should be restricted.
Now,
do I think that it is going to really be overused? You know, I don't know. I think that clearly if I do an endoscopy on
somebody and blow in too much air and they are in the recovery room vomiting,
my nurses will come to me and say, "You know, Zofran is good for
this." Are they then going to come
to me and say, "Hell, EMEND is potentially good for this"? They may.
But
I also think that what is out there and what is used for off‑label acute,
once, uses is probably good enough most of the time. It would be the chronic administration that I
think you are really worried about. And
I think you must put that in the label.
CHAIRPERSON
CAMILLERI: I think I have heard the same
message a few times. Any other comments
or questions pertaining to the additional information that we're providing to
the agency pertinent to question 4B? Do
you have any questions from the agency side?
Have we addressed this?
DR.
JUSTICE: No. I think you have been very helpful.
CHAIRPERSON
CAMILLERI: Okay. Question number 5, does the committee have
specific concerns regarding potential drug‑drug interactions with other
chemotherapeutic agents or other drug classes?
Do we think that we have already addressed this during the course of our
discussion? Yes, Dr. McLeod, please?
DR.
McLEOD: One thing that has been brought
up but hasn't been discussed ‑‑ and I don't think it needs to be
discussed, but it needs to be brought up again ‑‑ is the warfarin
interaction.
It
wasn't clear to me that the INR change that was seen was ‑‑ it
wasn't clear whether it was clinically relevant or not. And also because it was done in normal
volunteers, the dynamics of changes in warfarin metabolism are not always the
same as they are in patients, especially elderly patients, with a lot of co‑morbidity
and co‑medication.
So
I don't know what is required in that context, but certainly the applicant has
done a very nice job in showing that there is an issue there. It will always be flagged in the label, but I
think there may be some post‑marketing issues in the context of the age
groups in which cancer patients are seen.
So
there isn't a lot of warfarin use in childhood malignancy patients, at least
from my time at St. Jude, but in the adult side, where the average cancer
patient age is 65 to 70, in a general setting like that, there are a lot of
people on warfarin and not just for their afib and for their hip replacement,
not just for their cancer‑induced coagulopathy. And so it will be an issue that needs to be
better defined so that someone doesn't get in trouble, as Ms. Cohen mentioned.
CHAIRPERSON
CAMILLERI: Other recommendations or
comments?
(No
response.)
CHAIRPERSON
CAMILLERI: Okay. The final part of that question was, if yes,
please discuss them. I think we have
done that. Are there any other questions
or comments that need to be addressed?
Any questions, any final questions, from the agency side?
DR.
JUSTICE: No. Thanks.
We appreciate your work here.
CHAIRPERSON
CAMILLERI: On behalf of the agency side,
then I would like to thank all of the members, members of the public. I would like to thank the company for the
very thorough and clear presentations and our colleagues at the agency, who
provided a very good summary and important questions to make sure that if this
drug comes on the market and when it does, it is done in as safe a manner as
possible. Thank you very much.
We
are going to have a 15‑minute break.
And then we are going to come back for the closed session. Everybody else is excused.
(Whereupon, at 3:03 p.m., the
foregoing matter was adjourned and the meeting reconvened in closed session.)