Vaccine Pre-clinical Toxicology Testing
Vaccine Designs/Concepts
Correlates of Immunity
Assay Development
Animal Models
Immunologic Adjuvants
Variation
International Studies
Behavior
Ethics
Vaccine Design and Methodologic
Issues
Assay Validation
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Vaccine Pre-clinical Toxicology Testing
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- Acknowledgements
Glossary
Adjuvant - an immune enhancer added
to the active ingredient (i.e., antigen) of the vaccine to improve
immune responses - e.g., aluminum hydroxide or phosphate, IFA, CpG
motifs, cytokines. Currently, the only adjuvants in U.S. FDA licensed
vaccines are aluminum-containing formulations.
Bioburden - this term is often used
to indicate the "microbial limits" test promulgated in the U.S.
Pharmacopeia [25 USP <61>]. This is a test to measure the
number of micro-organisms present and to determine that none that
are present are "objectionable." Generally parenteral products should
be sterile, but if there is a terminal sterilization step, then
they may contain controlled levels of bioburden upstream.
Bulk - the drug
substance or the drug product which
has not been filled into final containers for distribution. Final
formulated bulk generally refers to drug product which is formulated
and being stored or held prior to filling. Drug substance may be
stored or held as "bulk" or "concentrated bulk" prior to formulation
into drug product.
21 CFR - Title 21 of the Code of Federal
Regulations gives FDA the authority to regulate biologics (like
vaccines), drugs, devices, etc., and investigational new drugs (including
investigational vaccines).
CMC - The Chemistry, Manufacturing, and
Controls section of the IND is the section in
which the sponsor describes the product: including, but not limited
to, the cell bank(s) characterization, adventitious agent testing,
manufacturing procedures for the drug substance, manufacturing procedures
for the formulation and filling of the drug product, in-process
controls, bulk and final container lot release controls and specifications,
release test methods, product characterization, and any other relevant
product information (e.g., excipients, raw materials, adjuvants,
delivery devices). For guidance on the content and format of the
CMC section of a vaccine IND, please refer to http://www.fda.gov/cber/gdlns/cmcvacc.pdf.
While this guidance document is intended to provide applicants with
information about what to submit in a Biologics License Application,
the guidance may also be useful in preparing a vaccine IND. For
further guidance on CMC section contents for a Phase 1 IND, please
refer to http://www.fda.gov/cber/gdlns/qaind1.pdf.
However, this latter document is not specific to vaccines. Finally,
for guidance on the CMC and other aspects of an IND for DNA vaccines,
please refer to http://www.fda.gov/cber/gdlns/plasmid.pdf.
COA - A certificate of analysis is the
document which lists the tests, methods, specifications, and results
of the in-process, bulk, and final
lot release tests for each bulk
and/or lot of drug, chemical, or vaccine manufactured. The COA should
be accompanied by the raw data or data worksheets to constitute
the lot release documents.
Drug Product - final formulated
vaccine with all excipients and adjuvant
(if any) at concentration or dosage to be used.
Drug Substance - unformulated
or partially formulated active ingredient (i.e., antigen or immunogen),
usually concentrated compared to final dosage to be used. There
may be multiple drug substances in a final drug product, such as
multiple strains (like poliovirus types 1, 2, and 3) or multiple
different antigens (like tetanus and diphtheria toxoids). Often
referred to as bulk or (monovalent) concentrate.
GLP - Good Laboratory Practices are like
GMP for laboratory and pre-clinical (i.e., animal)
studies and are defined in 21 CFR 58.
These regulations are all about control and documentation. Most
basic research laboratories do not naturally meet GLP standards.
Highlights of the requirements include, but are not limited to the
following:
- Requirement for a study director
- Requirement for a quality assurance unit
- Responsible for maintaining a Master Schedule Sheet of all
studies conducted
- Responsible for inspecting the study during its conduct
- Determine no deviations
- Review final report for accuracy
- Maintain records
- Facilities designed to
- Permit segregation necessary to ensure study integrity including:
- Areas for preparation of test and control articles
- Routine and specialized analytical procedures
- Separation of animal species
- Animals in different studies
- Quarantine of new animals
- Equipment must be inspected, cleaned, and maintained, including
calibration
- Written SOPs for these procedures
- Written records kept on these activities
- SOPs for routine procedures (listed examples in 21
CFR 58.81)
- Reagents appropriately labeled
- Animals healthy and specifically identified
- Test and control articles characterized for identity, strength
(potency), purity, and composition
- Manufacturing of test article documented
- Stability determined before or during study according to written
SOPs
- Uniformity of mixtures ensured, stability determined
- Study protocol prospectively written detailing specific study
(as opposed to SOPs which apply generically)
- Results recorded and raw data documented
- Records (including raw data) maintained for specified time periods
- Final report written documenting procedures, results, statistical
analyses
If this list seems extreme, you will understand why we might recommend
that you contract GLP studies with an experienced GLP facility.
GMP - Good Manufacturing Practices or
current GMP (cGMP) are defined by FDA in 21 CFR
210 and 211
and consist of regulations governing the procedures and practices
under which manufacturing is controlled (SOPs, training, lot release,
etc.) and quality of the manufacturing is assured (documentation,
batch records, certificates of analysis, records keeping, etc.)
GMPs are all about consistency, control, and documentation. GMPs
"...assure that such drug13 meets the
requirements of the [FD&C] act as to safety, and has the identity
and strength [potency] and meets the quality
and purity characteristics that it purports or is represented to
possess" (21 CFR 210.1).
GMPs ensure product reproducibility so the FDA and the public will
know that the vaccine delivered in clinical practice is the same
as that tested for licensure. Both the FDA (http://www.fda.gov/cber/gdlns/active.pdf)
and the ICH (http://www.ich.org)
have guidance documents on how to comply with cGMP. Highlights of
the requirements that constitute GMP include, but are not limited
to the following:
- requirement for a QC unit responsible for releasing or rejecting
lots, procedures, specifications
- personnel should be trained (including in cGMP) and that training
documented
- facilities should be suitably designed, cleaned, maintained
- design allows segregation and flow that prevents mix-ups and
cross-contaminations
- floors, walls, ceilings must be smooth, hard, and easily cleanable
- HEPA-filtered air handling under positive pressure
- systems in place for cleaning, disinfecting, aseptic handling,
including written procedures
- environmental controls
- freedom from vermin, including written procedures for use
of suitable methods for this control
- equipment
- designed so surfaces contacting the drug are not reactive,
additive, nor absorptive, nor alter the drug's specifications
- cleaned, maintained, and sanitized regularly, including written
procedures for doing so and records (logs) kept
- calibrated and inspected, incl. written procedures and records
kept (see the trend here!)
- computerized systems must be controlled so that records cannot
be altered and must be validated for accuracy
- filters don't release fibers into the product
- containers and closures
- stored to prevent contamination
- clean, sterilized (if appropriate), and pyrogen-free
- not reactive, additive, nor adsorptive
- raw materials quarantined until tested and released or rejected,
based on prospectively defined specifications
- segregation of components of different status (quarantined,
released, rejected)
- rotation of stocks of components
- production and process controls
- written procedures (SOPs)
- deviations recorded and justified
- yield calculated and calculations verified
- equipment used per batch identified and documented
- in-process controls and tests done on representative samples
- time limits for steps established and deviations documented
and justified
- environmental controls in place (microbiological contamination,
dust, etc.)
- prospective SOPs for re-processing
- SOPs for labeling and packaging controls
- records kept for labels accepted or rejected
- controls to reconcile quantities
- segregation to prevent mix-ups and cross-contamination during
labeling
- inspection to ensure accuracy
- expiration dating determined by stability testing and must appear
on labels
- written stability plan, results determine expiration dating
- written SOPs for warehousing and distribution
- lab procedures, sampling plans, specifications
- written procedures
- deviations recorded and justified
- controls on
- components
- containers/closures
- labeling
- in-process testing
- sampling
- calibrating instruments
- batches must meet prospective specifications before being released
- test methods validated for accuracy,
sensitivity, specificity, and reproducibility
- reserve samples must be retained for specific time-frames
- lab animal use is controlled and documented
- records maintained for specific time-frames, including raw data
- complaints, recalls, returns, investigations documented and
reviewed according to written procedures
- Master production records to ensure uniformity batch to batch
- Batch records
- Prepared for each batch documenting
- Dates
- Equipment used
- Batches of components used
- Personnel
- Control results
- Yield
- Samples taken
- Deviations and investigations
- Records must be reviewed
- Lab records documenting methods, personnel, etc.
- Records maintained on
- deviations and reasons,
- standardization of reference standards,
- calibration of equipment
- stability
- Distribution records maintained
If this list seems extreme, you will understand why we might recommend
that you contract GMP manufacturing with an experienced GMP facility.
GST - the general safety test. The methods
of the GST are promulgated in 21 CFR 610.11.
This final container test does not constitute nor substitute for
toxicology studies or adventitious agent tests. It is a test for
extraneous toxic contaminants which may have inadvertently been
introduced during formulation, filling, or storage.
ICFs - Informed Consent Forms
ICH - International Conference on Harmonisation
- a tripartite committee (EU, US, Japan) which has established harmonized
guidances that the participating regulatory control authorities
have agreed to follow. While the guidances do cover biotechnology
products, they do not uniformly cover vaccines; however, OVRR staff
do look to these guidances and follow them, if applicable. http://www.ich.org
IND - Investigational New Drug Application
- an IND is required to be filed with the FDA for investigational
products to be exempted from premarketing approval requirements
needed for interstate commerce. As of the 1997 Food and Drug Modernization
Act (FDAMA), there is a presumption of interstate commerce
for virtually everything because almost nothing can be made completely
intra-state. One gets one's culture media, flasks, pipettes, or
other components used in the manufacture of a vaccine candidate
through interstate commerce, therefore the investigational product
is considered to be in interstate commerce and must be exempted
by the filing of an IND in order to be studied in clinical trials.
If not exempt, unlicensed products can be seized and legal penalties
can be imposed on the investigators. For exact rules, reference
21 CFR 312
or contact FDA.
Investigators' Brochure (IB) - This document
and its contents are specified in 21 CFR 312.23(a)(5).
Essentially, all INDs require an IB except those conducted at a
single site by a single investigator who is the sponsor of the IND
(and who generally is also the manufacturer and responsible for
the performance of all pre-clinical studies). The IB is an important
tool for communicating information about the product, the pre-clinical
studies, and the proposed clinical protocol to the clinical investigator(s).
Lot Release - Each lot of product
must be controlled and only released for its intended use if it
meets prospectively defined quality control criteria (specifications).
Lots should be controlled at the levels of in-process tests, bulk(s),
and final container. Final containers must be controlled for identity,
purity, potency, sterility
(parenteral products) or bioburden (non-parenterals),
and the general safety test. Lot release documentation
should include the COA and the raw data or data
worksheets for all in-process, bulk, and final
container testing.
MSDS - Material Safety Data Sheet - an
OSHA requirement
NOAEL or NOEL - no observed adverse
effects level or no observed effects level - highest dose at which
no effect or adverse effect is seen in the animal studies - i.e.,
an "unquestionably" "safe" dose in that animal model. Generally
FDA considers risk/benefit when reviewing safety issues. But, when
no benefit has been shown (i.e., before any clinical studies have
been performed), balancing risk and unproven benefit is difficult.
Consequently, FDA may require starting studies at an unquestionably
safe dose level and escalation from there. Often, for vaccines,
the highest dose level tested turns out to be a NOAEL anyway (which
is why this term is not usually used in describing vaccines), but
in the event it's not, it's helpful to know what dosage is a NOAEL.
Pharmacology - for a vaccine,
pharmacology essentially means immunogenicity. However, this term
may also extend to actual drug pharmacology of an adjuvant, such
as a cytokine. The pharmacology/toxicology section of an IND
application should contain the results of all animal studies, including
formal toxicology, biodistribution (if applicable), attenuation
(if applicable), neurovirulence (if applicable), immunogenicity,
other specialized product-specific safety assessments, and challenge/protection
(if applicable). This section provides the justification for the
clinical dose selection and the safety of the product to go into
clinical trial(s).
Potency - Potency of a vaccine is
a little bit like the strength of a drug, but more complex. It's
not a factor proportional to the concentration of the active ingredient
(antigen) but rather to the immunogenicity of the drug
product (formulated antigen). So, just saying there's 300 mg
of gp120 or 1 mg of DNA there in the vial isn't sufficient, the
question is "is it immunogenic"? For FDA guidance on potency testing
of vaccines, you may wish to read Habig, Veterinary Microbiology,
37:343-51:1993. It concludes that a potency test should be reasonably
predicative of efficacy in humans, i.e., measure a parameter that
correlates with efficacy. Another important aspect to remember is
that it should be sufficiently quantitative, so that you can tell
if your vaccine has lost 30%, 50%, or 70% potency, for example.
Pre-IND - One of the perks of PDUFA2
and PDUFA3 (the Prescription Drug User Fee Act Reenactments) is
the assurance that FDA will hold a pre-IND meeting with you, if
you meet your end of the bargain (i.e., by following the rules and
by supplying them with sufficient information to evaluate your vaccine)
and it is not too premature or there is not some other significant
reason to deny it. The rules you need to follow (as well as the
rules FDA must follow) can be obtained at this link: http://www.fda.gov/cber/genadmin/pdufago111297.pdf
and scroll to section III on page 6 et seq. Section III.D. outlines
what you, as a sponsor, must do to properly request a pre-IND meeting.
The rest of Section III outlines what former DHHS Secretary Shalala
committed FDA to do. A guidance document on these procedures can
be obtained at http://www.fda.gov/cber/gdlns/mtpdufa.pdf.
[Please note that some of the timelines have changed slightly with
PDUFA3 - see http://www.fda.gov/oc/pdufa/PDUFAIIIGoals.html
for the latest.] Pre-IND meetings are an excellent opportunity to
find out what the FDA will require in order to permit a Phase 1
study to proceed with your specific product. If you do not hold
the pre-IND meeting with them, if you do not provide them with sufficient
information in the meeting materials to evaluate, and if you do
not ask them specific questions in order to permit them to give
you specific answers, you will miss this excellent opportunity and
may waste considerable effort and resources (including time, if
you are placed on clinical hold for not meeting their requirements).
SOP - Standard Operating Procedure - a
written document detailing all steps of a procedure and which you
actually follow without modification. Any deviations from the SOP
should be thoroughly investigated and outcomes of the investigation
documented (e.g., implementation of a new procedure).
Stability - For phase 1, stability
data should be provided in the IND to support
product quality through the length of the trial - what this means
is that some (generally 3 months' worth) real-time stability data
is provided in the Original Submission of the IND,
along with a plan to be testing on a frequent basis through the
conduct of the trial, so that if quality is lost, subjects can be
spared from receipt of a substandard, impotent product. Aspects
of stability that should be assessed are described in a guidance
document (intended for data to support licensure, but useful to
consider) which can be obtained at http://www.ich.org.
Briefly, a stability plan or protocol should include assessments
of critical parameters such as potency, purity,
sterility or bioburden,
pH, appearance, general safety, etc. Additionally,
for phase 1, stability data under actual clinical use conditions
should be provided to the IND to support the
proposed clinical protocol practice. In other words, if you are
going to reconstitute a lyophilized vaccine, thaw a frozen vaccine,
or remove from refrigerated temperatures a refrigerated vaccine;
draw up into a syringe or place into another vial or delivery device;
and deliver to the clinic for use within 2 hours, you should provide
FDA with data supporting that the quality and safety of the vaccine
is not lost during this process.
Sterility - FDA expects a particular
kind of sterility test to be performed and the methods are published
in 21 CFR 610.12.
Just any old sterility test will not do. Parenteral products generally
are required to be sterile.
Validation - the term "validation"
means very specific things to FDA and the ICH. For guidance on assay
validation (including what the term and related terms mean), please
try the following links: http://www.ich.org/
and http://www.ich.org/. Even
if your specific PCR assay is not validated, FDA will expect that
you have a handle on many of its performance characteristics (e.g.,
analytical "sensitivity" or limits of detection/quantitation - depending
on whether it's quantitative or not) and that you have "verified"
its suitability "under actual conditions of use," even if it is
not (yet) fully validated per the regulations as explained in the
above guidances. Assay parameter optimization is a separate process
that precedes assay validation and/or may be iterative with it (i.e.,
assay validation may identify parameters for which the assay should
have been optimized - after further optimization, the assay would
need to be re-validated.)
Vehicle - the excipients or matrix
in which the active ingredient (i.e., antigen) is prepared - e.g.,
PBS, sucrose-phosphate-glutamate (SPG), normal saline
13 FDA
applies the term "drug" to include biological products, including
vaccines. So, to FDA, a prophylactic vaccine is a drug (a prescription
drug).
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