The National Cancer Institute (NCI) has played an active
role in the development of drugs for cancer treatment for
over 40 years. This is reflected in the fact that approximately
one half of the chemotherapeutic drugs currently used by oncologists
for cancer treatment were discovered and/or developed at NCI.
The Developmental Therapeutics Program (DTP) promotes all
aspects of drug discovery and development before testing in
humans (preclinical development), and is a part of the Division
of Cancer Treatment and Diagnosis (DCTD). NCI also funds an
extensive clinical (human) trials network to ensure that promising
agents are tested in humans. NCI's Cancer Therapy Evaluation
Program (CTEP), also a part of DCTD, administers clinical
drug development. This fact sheet focuses primarily on preclinical
development within DTP. (http://dtp.nci.nih.gov/)
-
What role does the DTP play in drug development at
NCI?
DTP participates in all stages of pre-clinical drug discovery
and development. At the initial stage, DTP actively solicits
scientists for candidate drugs. A drug is first screened
in a variety of human tumor cell lines growing in tissue
culture dishes to test for its ability to prevent the
growth of specific kinds of tumor cells. If the drug shows
promise, extensive testing in animals will determine whether
it is effective and safe enough for testing in humans.
-
How long has NCI had a drug development program?
NCI has had some form of screening program to test experimental
cancer drugs since 1937, but it was not until 1955 that
a formal organization (called the Cancer Chemotherapy
National Service Center) was formed to integrate laboratory
resources with clinical facilities. Compounds in the early
decades were screened in leukemic mice, and in l975 a
program to screen mice bearing transplanted human tumors
was introduced. Over time, the system has evolved into
one that combines both in vitro (cancer cells grown in
a dish in the laboratory) with in vivo (animal) testing.
The current system, described in detail in question 5,
has been operational since l990.
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How many drugs has NCI tested?
DTP has over 400,000 drugs in its repository that have
gone through some kind of screening process at NCI. About
80,000 compounds have been screened since 1990, using
the current screening system.
-
Where do these drugs come from? How can they be characterized?
NCI actively solicits drugs from government laboratories,
research institutes, academic institutions, and companies
throughout the world. DTP scientists systematically scan
the latest literature for novel compounds and request
samples of promising drugs.
Another source of novel compounds comes from the Natural
Products Branch, a part of DTP, which collaborates with
agencies throughout the world to collect thousands of
plant and marine organisms for the tumor screen.
Although many drugs are voluntarily submitted, a substantial
fraction screened are solicited by NCI. Of all the drugs
screened by NCI, about 40 percent come from industry.
The remainder comes primarily from academic collaborators.
-
What are the specific stages of testing in DTP once
a drug has been chosen to be evaluated?
-
Preliminary in vitro screening: New drugs are first
evaluated in a pre-screen consisting of three human
tumor cell lines. Cells are exposed to each drug at
a single concentration for 48 hours. If growth of
one or more cell lines is inhibited, the drug is automatically
evaluated against the full panel of 60 human tumors.
-
In vitro screen in human tumors: Each drug is exposed
to 60 human tumor cell lines, including lung, colon,
melanoma, prostate, ovarian, breast and kidney cancers
at five different doses for 48 hours. Approximately
2,500 compounds are ested on a yearly basis. If the
drug is unique in some way - kills preferentially
one or more of the tumor cell lines, has a unique
mechanism of action, or can kill tumors at a very
small concentration - testing will proceed to the
next stage. About 2 percent of those screened will
be recommended for the next stage of testing in mice.
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In vivo testing using hollow-fiber technique: Small
hollow fibers (tubes 1 millimeter in diameter and
2 centimeters long made of a plastic, polyvinylidene
fluoride), containing cells from human tumors are
inserted underneath the skin and in the body cavity
of the mouse. Each candidate drug is administered
at two dosages and is tested against 12 target tumor
cells in different hollow fibers. A total of about
150-200 compounds/year is screened by this method.
Compounds that retard the growth of the cells are
recommended for the next level of testing. The average
length of this test is about four days.
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In vivo testing using xenografts: Human tumors are
injected directly below the skin of mice. Candidate
drugs which have shown evidence of activity in the
hollow fibers may be selected for testing in xenografts.
The drugs are administered to the mice at various
dosages, and those compounds that kill or slow down
the growth of specific tumors with minimal toxicity
to the animal will proceed to the next stage of testing.
The average length of this test is about 30 days.
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Pharmacology, formulation and toxicology studies:
Drugs that reach this stage of development are under
serious consideration for testing in humans so that
substantial resources may eventually be committed
to their development. There are two levels of development
at this stage.
-
At the first level of development, scientists
determine the basic pharmacology of the compound
in animals to see where the drug is metabolized.
The best chemical formulation for administering
the drug, how much of the drug to give, how often
and whether the drug should be taken orally or
by injection is also established.
-
If a drug progresses to the next level, NCI commits
substantial resources, approximately $250,000
to $500,000, to further development. A large-scale
production plan for the compound may be developed
if needed. In addition, toxicology evaluations
are done in two species of animals using the same
material under consideration for human trials.
If the drug has no serious problems, scientists
recommend the initial dose, route and schedule
for patients in early trials (phase I clinical
trials).
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What groups of people are responsible for decisions
at the various stages of development?
-
Access and Information Group, an interdisciplinary
group of scientists from DTP, makes recommendations
for the initial tumor screen. This committee makes
sure that each compound tested has a biological rationale
and novel chemical structure.
-
Screening Data and Review Committee, a group of biologists
and chemists from DTP, reviews the screening data
from the tumor cell lines and recommends which candidate
drugs should be tested in animals.
-
Biological Evaluation Committee (BEC), an interdisciplinary
group of 15 to 25 extramural scientists, meets monthly
to evaluate tumor screening and hollow fiber data.
The BEC makes recommendations to halt or proceed with
testing.
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Drug Development Group (DDG), an interdisciplinary
group of 15 to 25 NCI clinicians and scientists, meets
monthly to evaluate all the in vivo data from compounds
that are under serious consideration for testing in
humans. This group decides whether or not to recommend
a drug for human trials.
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What is the usual procedure for a company or academic
laboratory to enter into the process of NCI's drug development
program?
Compounds can enter at any stage of the development process
- with either very little or extensive prior testing.
A laboratory may only want its compound screened in tumor
lines. Alternatively, a compound may have been already
tested outside the NCI in tumor cell lines, requiring
only animal evaluation. Some compounds have been tested
in animals outside the NCI and are brought before the
DDG for approval to test in humans.
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What happens after the final testing in animals?
Once a drug is approved by the DDG, the next step is to
file an Investigational New Drug Application (IND) with
the Food and Drug Administration (FDA) to allow testing
in people. The IND describes the chemical structure of
the compound, how it is thought to work in the body, any
toxic effects found in the animals studies, how the compound
is produced and where and how the human trials will be
conducted. The IND may be submitted by NCI, a company
or an academic lab.
CTEP is responsible for submitting INDs for NCI as well
as drugs in which NCI is involved in a CRADA (Cooperative
Research and Development Agreement) or CTA (Clinical Trials
Agreement) with a company or supplier. NCI currently holds
nearly 200 INDs; many of these represent cooperative drug
development efforts with industry.
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What happens after the drug is approved by the FDA
for testing in humans?
The sponsor of the IND prepares a plan, or protocol, outlining
the institutions and number of people that will take part
in the study, the eligibility requirements, the medical
tests and interventions they will receive, and how often.
The protocol must be approved by NCI (or the organization
sponsoring the study) and the Institutional Review Board
(IRB) at each hospital or study site. This board, which
includes consumers, clergy, and health professionals,
reviews the protocol to ensure that the research will
not expose patients to extreme or unethical risks.
Once the centers and institutions have been selected and
protocols approved, phase I and phase II trials are conducted
with a limited number of people to determine the safety,
dosage, effectiveness, and the side effects of a drug.
If these preliminary trials indicate that the drug is
well-tolerated and shows some efficacy, phase III trials
are initiated. In phase III trials, hundreds of people
around the country are assigned at random to receive either
the new treatment, the standard treatment, or if no standard
treatment is effective, a placebo.
-
What groups carry out NCI-supported clinical trials?
NCI supports about 1,200 clinical trials through a variety
of programs. Some are conducted by NCI researchers at
the National Institutes of Health in Bethesda, Md., while
others take place at cancer centers, hospitals, and community
practices around the country.
The Clinical Trials Cooperative Groups (http://ctep.cancer.gov/resources/coop2.html)
are composed of academic institutions and cancer treatment
centers throughout the United States, Canada, and Europe,
and are made up of more than 1,500 institutions and 8,000
physicians that contribute patients to clinical trials.
The NCI Cancer Centers Program (http://cancercenters.cancer.gov)
comprises more than 50 NCI-designated cancer centers throughout
the country. Many cancer centers conduct NCI-approved
protocols and have web sites that provide information
about ongoing trials at their facilities.
The Community Clinical Oncology Program (CCOP) (http://www3.cancer.gov/prevention/ccop/)
provides support to community physicians and local hospitals
which are not a part of the Cooperative Groups so they
can participate in NCI-supported clinical trials. By affiliating
with either an NCI-supported clinical cooperative group
or cancer center, the 330 participating hospitals and
2,300 participating physicians in CCOP, can enter patients
into NCI-sponsored trials.
-
How many cancer patients participate in NCI-sponsored
clinical trials?
Each year about 25,000 new patients enter into NCI-sponsored
clinical trials. About 20,000 participate in Cooperative
Groups, 5,000 in the CCOPs, and 2,500 in trials conducted
at NIH in Bethesda, Md. This represents about 3 percent
of adult cancer patients and about 60 percent of children
who are diagnosed with cancer each year. Children under
age 20 account for about 1 percent of all cancer cases.
(http://www.cancer.gov/clinical_trials/
)
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What happens after Phase III trials?
At the conclusion of the phase III trials, the results
are reported at meetings and in peer-reviewed journals.
If the treatment is proven safe and effective in phase
III trials, the drug company sponsor of the drug files
a New Drug Application (NDA) with FDA. The average time
for FDA approval is six months to a year. Once approved
by FDA, the drug becomes available for physicians to prescribe
for patients.
-
About how long does the entire drug approval process
take?
It takes about 15 years on average for an experimental
cancer drug to travel from the lab to patients. Preclinical
testing takes about six and a half years and phase I,
II, and III clinical trials about seven years to complete.
The time between filing the results of the completed clinical
trials with FDA (NDA) and the drug's approval by FDA is
about six months to two years. At this point, doctors
can prescribe the drug.
-
Does NCI have mechanisms for ensuring privacy of the
test results when working with private industry?
Yes, in order to encourage collaborations with private
industry, procedures were developed for confidential handling
of proprietary chemicals, called the Discreet Screening
Agreement. All screening data are returned to the supplier.
-
What is the success ratio for drug development?
From 1990 through October 1998:
-
70,702 compounds were selected for screening by Access
and Information Group;
-
6,452 of those showed potential activity 1,546 of
those were chosen by the Biological Evaluation Committee
for testing in mice;
-
79 of those were effective in killing or slowing
the growth of human tumor cells, and
-
10 were approved by the DDG for human testing after
further toxicity studies in animals.
So about one to two out of every 10,000 drugs screened
in human tumor lines is tested in human trials. Typically,
only 20 percent of those tested in early human trials
(phase I) are finally approved by FDA for commercial use.
-
What is unique about the screening program at NCI?
The NCI focuses on scientific merit and uniqueness. In
particular, NCI scientists are looking for drugs with
novel mechanisms of action.
-
What are some success stories? What drugs developed
by DTP at NCI are now in commercial use?
Half of the FDA-approved anticancer drugs were sponsored
by NCI. For example, cisplatin for treating testicular,
ovarian, and lung cancer, and paclitaxel (Taxol®) and
fludarabine phosphate for treating several cancers and
lymphoma, respectively are examples where NCI involvement
in early stage of development resulted in products which
eventually were licensed to commercial organizations and
reached the market.
Other examples include:
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Alkylating Agents: BCNU, Carboplatin, DTIC
-
Anti-metabolite: Ara-C, Pentostatin
-
Synthetics: Hydroxyurea, Mitoxantrone, Topotecan
-
What are some of the new directions for NCI's drug
development program?
-
This year sees the initiation of the Molecular Targets
Drug Discovery Program which provides support to take
advantage of new knowledge in cancer-related molecular
targets and pathways. Forty research groups are currently
supported by this program. (http://dtp.nci.nih.gov/branches/gcob/gcob_web9.html)
-
NCI's drug portfolio has expanded to included a variety
of new molecular and cellular therapeutic targets
and approaches, including: angiogenesis inhibitors,
tumor vaccines, antibodies, immunotoxins, and antisense
oligonucleotides.
-
Rather than testing only to see whether drugs are
effective against particular tumors, the screening
program is testing whether drugs are effective against
specific gene mutations in tumors. For example, researchers
are screening yeast mutant cell lines (which have
been engineered to have only single gene mutations)
with the vast NCI drug repository to see if certain
drugs are effective against specific mutations.
-
RAID (Rapid Access to Intervention Development) is
a new program (8/98) designed to speed up the pre-clinical
testing for promising drugs. The RAID program is intended
to target academic laboratories that have novel candidate
compounds, but lack specific resources or expertise.
By applying for aid on specific drug development tasks,
academic researchers across the country can have access
to NCI's resources. Some tasks that are supported
by RAID include: developing a formulation of a drug
that is suitable for humans, scaling up the production
of a drug to the level needed for human trials, and
conducting stability and toxicology tests on a candidate
drug. (http://dtp.nci.nih.gov/docs/raid/raid%5Fpp%5Fold.html)
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What are some promising drugs under consideration
now?
NCI is supporting the development of drugs that target
many biochemical pathways in the cell - genes involved
in apoptosis, cell cycle control and cell signaling, angiogenesis,
tumor invasion and metastasis, DNA synthesis and immune
functions. Some of the promising agents and their biochemical
pathways that are in early clinical development at NCI
include:
Antibodies to VEGF integrins
|
O6 Benzylguanine: alters DNA repair
|
OSI-774 (OSI Pharmaceuticals) and Iressa (Astra
Zeneca): inhibitors of growth factor signaling
|
Flavopiridol (Aventis) and UCN-01 (Kyowa Hakko
Kogyo): cell cycle
|
CAI: anti-metastasis and anti-angiogenesis
|
Rapamycin analogs (Wyeth-Ayerst): cell cycle function
|
Rebeccamycin: topoisomerase inhibitor
|
Halichondrin analogs (Eisai Co.): inhibits tubulin
formation
|
Pyrrolobenzodiazepine: alters DNA function
|
KRN5500: mechanism uncertain
|
FR901228: binds to multi-drug resistance gene product
|
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What are other sources of information about drug development
at NCI?
-
Chapter 11,"New Targets for Cancer Chemotherapy"
by Susan G. Arbuck, Janet Dancey, James M. Pluda,
Louise Grochow, Anthony J. Murgo, Percy Ivy, John
Wright, Barbara Blaylock, Laura E. Via and Edward
A. Sausville, M.D., Ph.D., from Cancer Chemotherapy
and Biological Response Modifiers Annual 19, edited
by G. Giaccone, R. Schilsky and P. Sondel. Elsevier
Science B.V., 2001.
-
"Evolving Approaches to Cancer Drug Discovery and
Development at the National Cancer Institute" by E.
A. Sausville and E. Feigal in Annals of Oncology,
No.10, September, 1999, 1287-1291.
-
"Molecules for the Millennium: How Will They Look?
New Drug Discovery Year 2000" by E. A. Sausville and
J.I. Johnson in British Journal of Cancer, Vol. 83,
No.11, August, 2000, 1401-1404.
Web sites:
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