Guidance for Industry

S6 Preclinical Safety Evaluation of

Biotechnology-Derived

Pharmaceuticals

July 1997

ICH
Guidance for Industry

S6 Preclinical Safety Evaluation of

Biotechnology-Derived

Pharmaceuticals

Additional copies are available from:

 the Drug Information Branch (HFD-210),

Center for Drug Evaluation and Research (CDER),

5600 Fishers Lane, Rockville, MD 20857 (Tel) 301-827-4573

http://www.fda.gov/cder/guidance/index.htm

or

Office of Communication,

Training, and Manufacturers Assistance (HFM-40)

Center for Biologics Evaluation and Research (CBER)

1401 Rockville Pike, Rockville, MD 20852-1448,

http://www.fda.gov/cber/guidelines.htm

(Fax) 888-CBERFAX or 301-827-3844

(Voice Information) 800-835-4709 or 301-827-1800

U.S. Department of Health and Human Services

Food and Drug Administration

Center for Drug Evaluation and Research (CDER)

Center for Biologics Evaluation and Research (CBER)

July 1997

ICH
i

Table of Contents

I. INTRODUCTION (1) .................................................. 1

A. Background (1.1) ................................................ 1

B. Objectives (1.2) ................................................. 1

C. Scope (1.3) ..................................................... 2

II. SPECIFICATION OF THE TEST MATERIAL (2) ............................ 2

III. PRECLINICAL SAFETY TESTING (3) .................................... 3

A. General Principles (3.1) ........................................... 3

B. Biological Activity/Pharmacodynamics (3.2) ............................ 3

C. Animal Species/Model Selection (3.3) ................................ 4

D. Number/Gender of Animals (3.4) .................................... 5

E. Administration/Dose Selection (3.5) .................................. 5

F. Immunogenicity (3.6) ............................................. 6

IV. SPECIFIC CONSIDERATIONS (4) ....................................... 7

A. Safety Pharmacology (4.1) ......................................... 7

B. Exposure Assessment (4.2) ......................................... 7

C. Single Dose Toxicity Studies (4.3) ................................... 8

D. Repeated Dose Toxicity Studies (4.4) ................................. 8

E. Immunotoxicity Studies (4.5) ....................................... 9

F. Reproductive Performance and Developmental Toxicity Studies (4.6) ......... 9

G. Genotoxicity Studies (4.7) ......................................... 9

H. Carcinogenicity Studies (4.8) ...................................... 10

I. Local Tolerance Studies (4.9) ...................................... 10

NOTES .................................................................. 11
 This guidance was developed within the Expert Working Group (Safety) of the International Conference on 1

Harmonisation of Technical Requirements for Registration of Pharmaceuticals for Human Use (ICH) and has been

subject to consultation by the regulatory parties, in accordance with the ICH process. This document has been endorsed

by the ICH Steering Committee at Step 4 of the ICH process, July 1997. At Step 4 of the process, the final draft is

recommended for adoption to the regulatory bodies of the European Union, Japan and the United States. This guidance

was published in the Federal Register on November 18, 1997 (62 FR 61515), and is applicable to drug and biological

products. This guidance represents the Agency’s current thinking on preclinical safety evaulation of biotechnologyderived pharmaceuticals. It does not create or confer any rights for or on any person and does not operate to bind FDA

or the public. An alternative approach may be used if such approach satisfies the requirements of the applicable statute,

regulations, or both.

GUIDANCE FOR INDUSTRY1

S6 Preclinical Safety Evaluation of

Biotechnology-Derived Pharmaceuticals

I. INTRODUCTION (1)

A. Background (1.1)

Biotechnology-derived pharmaceuticals (biopharmaceuticals) were initially developed in the early

1980's. The first marketing authorizations were granted later in the decade. Several guidelines

and points-to-consider documents have been issued by various regulatory agencies regarding

safety assessment of these products. Review of such documents, which are available from

regulatory authorities, may provide useful background in developing new biopharmaceuticals.

Considerable experience has now been gathered with submission of applications for

biopharmaceuticals. Critical review of this experience has been the basis for development of this

guidance, which is intended to provide general principles for designing scientifically acceptable

preclinical safety evaluation programs. 

B. Objectives (1.2)

Regulatory standards for biotechnology-derived pharmaceuticals have generally been comparable

among the European Union, Japan, and the United States. All three regions have adopted a

flexible, case-by-case, science-based approach to preclinical safety evaluation needed to support

clinical development and marketing authorization. In this rapidly evolving scientific area, there is a

need for common understanding and continuing dialogue among the regions. 

The primary goals of preclinical safety evaluation are: (1) To identify an initial safe dose and

subsequent dose escalation schemes in humans; (2) to identify potential target organs for toxicity

and for the study of whether such toxicity is reversible; and (3) to identify safety parameters for

clinical monitoring. Adherence to the principles presented in this document should improve the
2

quality and consistency of the preclinical safety data supporting the development of

biopharmaceuticals.

C. Scope (1.3)

This guidance is intended primarily to recommend a basic framework for the preclinical safety

evaluation of biotechnology-derived pharmaceuticals. It applies to products derived from

characterized cells through the use of a variety of expression systems including bacteria, yeast,

insect, plant, and mammalian cells. The intended indications may include in vivo diagnostic,

therapeutic, or prophylactic uses. The active substances include proteins and peptides, their

derivatives, and products of which they are components; they could be derived from cell cultures

or produced using recombinant deoxyribonucleic acid (DNA) technology, including production by

transgenic plants and animals. Examples include but are not limited to: Cytokines, plasminogen

activators, recombinant plasma factors, growth factors, fusion proteins, enzymes, receptors,

hormones, and monoclonal antibodies.

The principles outlined in this guidance may also be applicable to recombinant DNA protein

vaccines, chemically synthesized peptides, plasma derived products, endogenous proteins

extracted from human tissue, and oligonucleotide drugs. 

This document does not cover antibiotics, allergenic extracts, heparin, vitamins, cellular blood

components, conventional bacterial or viral vaccines, DNA vaccines, or cellular and gene

therapies.

II. SPECIFICATION OF THE TEST MATERIAL (2)

Safety concerns may arise from the presence of impurities or contaminants. It is preferable to rely

on purification processes to remove impurities and contaminants rather than to establish a

preclinical testing program for their qualification. In all cases, the product should be sufficiently

characterized to allow an appropriate design of preclinical safety studies. 

There are potential risks associated with host cell contaminants derived from bacteria, yeast,

insect, plants, and mammalian cells. The presence of cellular host contaminants can result in

allergic reactions and other immunopathological effects. The adverse effects associated with

nucleic acid contaminants are theoretical but include potential integration into the host genome. 

For products derived from insect, plant, and mammalian cells, or transgenic plants and animals,

there may be an additional risk of viral infections. 

In general, the product that is used in the definitive pharmacology and toxicology studies should

be comparable to the product proposed for the initial clinical studies. However, it is appreciated

that during the course of development programs, changes normally occur in the manufacturing
3

process in order to improve product quality and yields. The potential impact of such changes for

extrapolation of the animal findings to humans should be considered.

The comparability of the test material during a development program should be demonstrated

when a new or modified manufacturing process is developed or other significant changes in the

product or formulation are made in an ongoing development program. Comparability can be

evaluated on the basis of biochemical and biological characterization (i.e., identity, purity,

stability, and potency). In some cases, additional studies may be needed (i.e., pharmacokinetics,

pharmacodynamics and/or safety). The scientific rationale for the approach taken should be

provided. 

III. PRECLINICAL SAFETY TESTING (3)

A. General Principles (3.1)

The objectives of the preclinical safety studies are to define pharmacological and toxicological

effects not only prior to initiation of human studies but throughout clinical development. Both in

vitro and in vivo studies can contribute to this characterization. Biopharmaceuticals that are

structurally and pharmacologically comparable to a product for which there is wide experience in

clinical practice may need less extensive toxicity testing.

Preclinical safety testing should consider: (1) Selection of the relevant animal species; (2) age; (3)

physiological state; (4) the manner of delivery, including dose, route of administration, and

treatment regimen; and (5) stability of the test material under the conditions of use. 

Toxicity studies are expected to be performed in compliance with Good Laboratory Practice

(GLP); however, it is recognized that some studies employing specialized test systems, which are

often needed for biopharmaceuticals, may not be able to comply fully with GLP. Areas of

noncompliance should be identified and their significance evaluated relative to the overall safety

assessment. In some cases, lack of full GLP compliance does not necessarily mean that the data

from these studies cannot be used to support clinical trials and marketing authorizations. 

Conventional approaches to toxicity testing of pharmaceuticals may not be appropriate for

biopharmaceuticals due to the unique and diverse structural and biological properties of the latter

that may include species specificity, immunogenicity, and unpredicted pleiotropic activities. 

B. Biological Activity/Pharmacodynamics (3.2)

Biological activity may be evaluated using in vitro assays to determine which effects of the

product may be related to clinical activity. The use of cell lines and/or primary cell cultures can be

useful to examine the direct effects on cellular phenotype and proliferation. Due to the species

specificity of many biotechnology-derived pharmaceuticals, it is important to select relevant
4

animal species for toxicity testing. In vitro cell lines derived from mammalian cells can be used to

predict specific aspects of in vivo activity and to assess quantitatively the relative sensitivity of

various species (including human) to the biopharmaceutical. Such studies may be designed to

determine, for example, receptor occupancy, receptor affinity, and/or pharmacological effects, and

to assist in the selection of an appropriate animal species for further in vivo pharmacology and

toxicology studies. The combined results from in vitro and in vivo studies assist in the

extrapolation of the findings to humans. In vivo studies to assess pharmacological activity,

including defining mechanism(s) of action, are often used to support the rationale of the proposed

use of the product in clinical studies. 

For monoclonal antibodies, the immunological properties of the antibody should be described in

detail, including its antigenic specificity, complement binding, and any unintentional reactivity

and/or cytotoxicity towards human tissues distinct from the intended target. Such cross-reactivity

studies should be carried out by appropriate immunohistochemical procedures using a range of

human tissues. 

C. Animal Species/Model Selection (3.3)

The biological activity together with species and/or tissue specificity of many biotechnologyderived pharmaceuticals often preclude standard toxicity testing designs in commonly used

species (e.g., rats and dogs). Safety evaluation programs should include the use of relevant

species. A relevant species is one in which the test material is pharmacologically active due to the

expression of the receptor or an epitope (in the case of monoclonal antibodies). A variety of

techniques (e.g., immunochemical or functional tests) can be used to identify a relevant species. 

Knowledge of receptor/epitope distribution can provide greater understanding of potential in vivo

toxicity.

Relevant animal species for testing of monoclonal antibodies are those that express the desired

epitope and demonstrate a similar tissue cross-reactivity profile as for human tissues. This would

optimize the ability to evaluate toxicity arising from the binding to the epitope and any

unintentional tissue cross-reactivity. An animal species that does not express the desired epitope

may still be of some relevance for assessing toxicity if comparable unintentional tissue crossreactivity to humans is demonstrated. 

Safety evaluation programs should normally include two relevant species. However, in certain

justified cases one relevant species may suffice (e.g., when only one relevant species can be

identified or where the biological activity of the biopharmaceutical is well understood). In

addition, even where two species may be necessary to characterize toxicity in short term studies,

it may be possible to justify the use of only one species for subsequent long-term toxicity studies

(e.g., if the toxicity profile in the two species is comparable in the short term). 

Toxicity studies in nonrelevant species may be misleading and are discouraged. When no relevant

species exists, the use of relevant transgenic animals expressing the human receptor or the use of
5

homologous proteins should be considered. The information gained from use of a transgenic

animal model expressing the human receptor is optimized when the interaction of the product and

the humanized receptor has similar physiological consequences to those expected in humans. 

While useful information may also be gained from the use of homologous proteins, it should be

noted that the production process, range of impurities/contaminants, pharmacokinetics, and exact

pharmacological mechanism(s) may differ between the homologous form and the product

intended for clinical use. Where it is not possible to use transgenic animal models or homologous

proteins, it may still be prudent to assess some aspects of potential toxicity in a limited toxicity

evaluation in a single species, e.g., a repeated dose toxicity study of < 14 days duration that

includes an evaluation of important functional endpoints (e.g., cardiovascular and respiratory). 

In recent years, there has been much progress in the development of animal models that are

thought to be similar to the human disease. These animal models include induced and

spontaneous models of disease, gene knockout(s), and transgenic animals. These models may

provide further insight, not only in determining the pharmacological action of the product,

pharmacokinetics, and dosimetry, but may also be useful in the determination of safety (e.g.,

evaluation of undesirable promotion of disease progression). In certain cases, studies performed

in animal models of disease may be used as an acceptable alternative to toxicity studies in normal

animals (Note 1). The scientific justification for the use of these animal models of disease to

support safety should be provided. 

D. Number/Gender of Animals (3.4)

The number of animals used per dose has a direct bearing on the ability to detect toxicity. A small

sample size may lead to failure to observe toxic events due to observed frequency alone regardless

of severity. The limitations that are imposed by sample size, as often is the case for nonhuman

primate studies, may be in part compensated by increasing the frequency and duration of

monitoring. Both genders should generally be used or justification given for specific omissions. 

E. Administration/Dose Selection (3.5)

The route and frequency of administration should be as close as possible to that proposed for

clinical use. Consideration should be given to pharmacokinetics and bioavailability of the product

in the species being used and to the volume which can be safely and humanely administered to the

test animals. For example, the frequency of administration in laboratory animals may be increased

compared to the proposed schedule for the human clinical studies in order to compensate for

faster clearance rates or low solubility of the active ingredient. In these cases, the level of

exposure of the test animal relative to the clinical exposure should be defined. Consideration

should also be given to the effects of volume, concentration, formulation, and site of

administration. The use of routes of administration other than those used clinically may be

acceptable if the route must be modified due to limited bioavailability, limitations due to the route

of administration, or to size/physiology of the animal species. 
6

Dosage levels should be selected to provide information on a dose-response relationship,

including a toxic dose and a no observed adverse effect level (NOAEL). For some classes of

products with little to no toxicity, it may not be possible to define a specific maximum dose. In

these cases, a scientific justification of the rationale for the dose selection and projected multiples

of human exposure should be provided. To justify high dose selection, consideration should be

given to the expected pharmacological/physiological effects, availability of suitable test material,

and the intended clinical use. Where a product has a lower affinity to or potency in the cells of the

selected species than in human cells, testing of higher doses may be important. The multiples of

the human dose that are needed to determine adequate safety margins may vary with each class of

biotechnology-derived pharmaceutical and its clinical indication(s). 

F. Immunogenicity (3.6)

Many biotechnology-derived pharmaceuticals intended for humans are immunogenic in animals. 

Therefore, measurement of antibodies associated with administration of these types of products

should be performed when conducting repeated dose toxicity studies in order to aid in the

interpretation of these studies. Antibody responses should be characterized (e.g., titer, number of

responding animals, neutralizing or non-neutralizing) and their appearance should be correlated

with any pharmacological and/or toxicological changes. Specifically, the effects of antibody

formation on pharmacokinetic/pharmacodynamic parameters, incidence and/or severity of adverse

effects, complement activation, or the emergence of new toxic effects should be considered when

interpreting the data. Attention should also be paid to the evaluation of possible pathological

changes related to immune complex formation and deposition.

The detection of antibodies should not be the sole criterion for the early termination of a

preclinical safety study or modification in the duration of the study design unless the immune

response neutralizes the pharmacological and/or toxicological effects of the biopharmaceutical in

a large proportion of the animals. In most cases, the immune response to biopharmaceuticals is

variable, like that observed in humans. If the interpretation of the data from the safety study is not

compromised by these issues, then no special significance should be ascribed to the antibody

response. 

The induction of antibody formation in animals is not predictive of a potential for antibody

formation in humans. Humans may develop serum antibodies against humanized proteins, and

frequently the therapeutic response persists in their presence. The occurrence of severe

anaphylactic responses to recombinant proteins is rare in humans. In this regard, the results of

guinea pig anaphylaxis tests, which are generally positive for protein products, are not predictive

for reactions in humans; therefore, such studies are considered of little value for the routine

evaluation of these types of products.
7

IV. SPECIFIC CONSIDERATIONS (4)

A. Safety Pharmacology (4.1)

It is important to investigate the potential for undesirable pharmacological activity in appropriate

animal models and, where necessary, to incorporate particular monitoring for these activities in

the toxicity studies and/or clinical studies. Safety pharmacology studies measure functional

indices of potential toxicity. These functional indices may be investigated in separate studies or

incorporated in the design of toxicity studies. The aim of the safety pharmacology studies should

be to reveal any functional effects on the major physiological systems (e.g., cardiovascular,

respiratory, renal, and central nervous systems). Investigations may also include the use of

isolated organs or other test systems not involving intact animals. All of these studies may allow

for a mechanistically-based explanation of specific organ toxicities, which should be considered

carefully with respect to human use and indication(s). 

B. Exposure Assessment (4.2)

1. Pharmacokinetics and Toxicokinetics (4.2.1)

It is difficult to establish uniform guidances for pharmacokinetic studies for biotechnologyderived pharmaceuticals. Single and multiple dose pharmacokinetics, toxicokinetics, and

tissue distribution studies in relevant species are useful; however, routine studies that

attempt to assess mass balance are not useful. Differences in pharmacokinetics among

animal species may have a significant impact on the predictiveness of animal studies or on

the assessment of dose-response relationships in toxicity studies. Alterations in the

pharmacokinetic profile due to immune-mediated clearance mechanisms may affect the

kinetic profiles and the interpretation of the toxicity data. For some products, there may

also be inherent, significant delays in the expression of pharmacodynamic effects relative

to the pharmacokinetic profile (e.g., cytokines) or there may be prolonged expression of

pharmacodynamic effects relative to plasma levels. 

Pharmacokinetic studies should, whenever possible, utilize preparations that are

representative of those intended for toxicity testing and clinical use and employ a route of

administration that is relevant to the anticipated clinical studies. Patterns of absorption

may be influenced by formulation, concentration, site, and/or volume. Whenever possible,

systemic exposure should be monitored during the toxicity studies. 

When using radiolabeled proteins, it is important to show that the radiolabeled test

material maintains activity and biological properties equivalent to that of the unlabeled

material. Tissue concentrations of radioactivity and/or autoradiography data using

radiolabeled proteins may be difficult to interpret due to rapid in vivo metabolism or

unstable radiolabeled linkage. Care should be taken in the interpretation of studies using
8

radioactive tracers incorporated into specific amino acids because of recycling of amino

acids into nondrug related proteins/peptides.

Some information on absorption, disposition, and clearance in relevant animal models

should be available prior to clinical studies in order to predict margins of safety based

upon exposure and dose. 

2. Assays (4.2.2)

The use of one or more assay methods should be addressed on a case-by-case basis and

the scientific rationale should be provided. One validated method is usually considered

sufficient. For example, quantitation of TCA-precipitable radioactivity following

administration of a radiolabeled protein may provide adequate information, but a specific

assay for the analyte is preferred. Ideally, the assay methods should be the same for

animals and humans. The possible influence of plasma binding proteins and/or antibodies

in plasma/serum on the assay performance should be determined.

3 Metabolism (4.2.3)

The expected consequence of metabolism of biotechnology-derived pharmaceuticals is the

degradation to small peptides and individual amino acids. Therefore, the metabolic

pathways are generally understood. Classical biotransformation studies as performed for

pharmaceuticals are not needed. 

Understanding the behavior of the biopharmaceutical in the biologic matrix (e.g., plasma,

serum, cerebral spinal fluid) and the possible influence of binding proteins is important for

understanding the pharmacodynamic effect. 

C. Single Dose Toxicity Studies (4.3)

Single dose studies may generate useful data to describe the relationship of dose to systemic

and/or local toxicity. These data can be used to select doses for repeated dose toxicity studies. 

Information on dose-response relationships may be gathered through the conduct of a single dose

toxicity study or as a component of pharmacology or animal model efficacy studies. The

incorporation of safety pharmacology parameters in the design of these studies should be

considered.

D. Repeated Dose Toxicity Studies (4.4)

For consideration of the selection of animal species for repeated dose studies, see section III.C

(3.3). The route and dosing regimen (e.g., daily versus intermittent dosing) should reflect the

intended clinical use or exposure. When feasible, these studies should include toxicokinetics.
9

A recovery period should generally be included in study designs to determine the reversal or

potential worsening of pharmacological/toxicological effects, and/or potential delayed toxic

effects. For biopharmaceuticals that induce prolonged pharmacological/toxicological effects,

recovery group animals should be monitored until reversibility is demonstrated. The duration of

repeated dose studies should be based on the intended duration of clinical exposure and disease

indication. This duration of animal dosing has generally been 1-3 months for most biotechnologyderived pharmaceuticals. For biopharmaceuticals intended for short-term use (e.g., < to 7 days)

and for acute life-threatening diseases, repeated dose studies up to 2 weeks duration have been

considered adequate to support clinical studies as well as marketing authorization. For those

biopharmaceuticals intended for chronic indications, studies of 6 months duration have generally

been appropriate, although in some cases shorter or longer durations have supported marketing

authorizations. For biopharmaceuticals intended for chronic use, the duration of long-term

toxicity studies should be scientifically justified.

E. Immunotoxicity Studies (4.5)

One aspect of immunotoxicological evaluation includes assessment of potential immunogenicity

(see section III.F (3.6)). Many biotechnology-derived pharmaceuticals are intended to stimulate

or suppress the immune system and, therefore, may affect not only humoral but also cell-mediated

immunity. Inflammatory reactions at the injection site may be indicative of a stimulatory

response. It is important, however, to recognize that simple injection trauma and/or specific toxic

effects caused by the formulation vehicle may also result in toxic changes at the injection site. In

addition, the expression of surface antigens on target cells may be altered, which has implications

for autoimmune potential. Immunotoxicological testing strategies may require screening studies

followed by mechanistic studies to clarify such issues. Routine tiered testing approaches or

standard testing batteries, however, are not recommended for biotechnology-derived

pharmaceuticals.

F. Reproductive Performance and Developmental Toxicity Studies (4.6)

The need for reproductive/developmental toxicity studies is dependent upon the product, clinical

indication and intended patient population (Note 2). The specific study design and dosing

schedule may be modified based on issues related to species specificity, immunogenicity,

biological activity, and/or a long elimination half-life. For example, concerns regarding potential

developmental immunotoxicity, which may apply particularly to certain monoclonal antibodies

with prolonged immunological effects, could be addressed in a study design modified to assess

immune function of the neonate. 

G. Genotoxicity Studies (4.7)

The range and type of genotoxicity studies routinely conducted for pharmaceuticals are not

applicable to biotechnology-derived pharmaceuticals and therefore are not needed. Moreover, the

administration of large quantities of peptides/proteins may yield uninterpretable results. It is not
10

expected that these substances would interact directly with DNA or other chromosomal material

(Note 3). 

Studies in available and relevant systems, including newly developed systems, should be

performed in those cases where there is cause for concern about the product (e.g., because of the

presence of an organic linker molecule in a conjugated protein product). The use of standard

genotoxicity studies for assessing the genotoxic potential of process contaminants is not

considered appropriate. If performed for this purpose, however, the rationale should be provided.

H. Carcinogenicity Studies (4.8)

Standard carcinogenicity bioassays are generally inappropriate for biotechnology-derived

pharmaceuticals. However, product-specific assessment of carcinogenic potential may still be

needed depending upon duration of clinical dosing, patient population, and/or biological activity

of the product (e.g., growth factors, immunosuppressive agents, etc.). When there is a concern

about carcinogenic potential, a variety of approaches may be considered to evaluate risk. 

Products that may have the potential to support or induce proliferation of transformed cells and

clonal expansion possibly leading to neoplasia should be evaluated with respect to receptor

expression in various malignant and normal human cells that are potentially relevant to the patient

population under study. The ability of the product to stimulate growth of normal or malignant

cells expressing the receptor should be determined. When in vitro data give cause for concern

about carcinogenic potential, further studies in relevant animal models may be needed. 

Incorporation of sensitive indices of cellular proliferation in long-term repeated dose toxicity

studies may provide useful information.

In those cases where the product is biologically active and nonimmunogenic in rodents and other

studies have not provided sufficient information to allow an assessment of carcinogenic potential,

then the utility of a single rodent species should be considered. Careful consideration should be

given to the selection of doses. The use of a combination of pharmacokinetic and

pharmacodynamic endpoints with consideration of comparative receptor characteristics and

intended human exposures represents the most scientifically based approach for defining the

appropriate doses. The rationale for the selection of doses should be provided. 

I. Local Tolerance Studies (4.9)

Local tolerance should be evaluated. The formulation intended for marketing should be tested;

however, in certain justified cases, the testing of representative formulations may be acceptable. 

In some cases, the potential adverse effects of the product can be evaluated in single or repeated

dose toxicity studies, thus obviating the need for separate local tolerance studies.
11

NOTES

Note 1. Animal models of disease may be useful in defining toxicity endpoints, selection of clinical

indications, and determination of appropriate formulations, route of administration, and treatment

regimen. It should be noted that with these models of disease there is often a paucity of historical

data for use as a reference when evaluating study results. Therefore, the collection of concurrent

control and baseline data is critical to optimize study design.

Note 2. There may be extensive public information available regarding potential reproductive

and/or developmental effects of a particular class of compounds (e.g., interferons) where the only

relevant species is the nonhuman primate. In such cases, mechanistic studies indicating that

similar effects are likely to be caused by a new but related molecule may obviate the need for

formal reproductive/developmental toxicity studies. In each case, the scientific basis for assessing

the potential for possible effects on reproduction/development should be provided.

Note 3. With some biopharmaceuticals, there is a potential concern about accumulation of

spontaneously mutated cells (e.g., via facilitating a selective advantage of proliferation) leading to

carcinogenicity. The standard battery of genotoxicity tests is not designed to detect these

conditions. Alternative in vitro or in vivo models to address such concerns may have to be

developed and evaluated.