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2. Nonclinical development of monovalent and polyvalent biopharmaceuticals56
I. Development of biopharmaceuticals
3
Regulatory guidelines and their
application in the nonclinical
evaluation of biological medicines
Claudette L. Fuller
1
, Maggie Dempster
2, a
and
Marque D. Todd
3
1
Non-Clinical Safety and Toxicology, Genmab, Plainsboro, NJ, United States;
2
GSK,
Collegeville, PA, United States;
3
Renaissance Consulting, Inc., Escondido, CA, United States
OUTLINE
Introduction 58
Species selection 61
Selecting a relevant species 62
Screening paradigms 62
Use of tissue cross-reactivity assays 64
When a relevant species cannot be
identified? 65
Study design considerations for repeat-
dose studi es 66
Safety pharmacology endpoints 68
Dose sel ection 68
Route of administration 69
Recovery periods for repeat-dose studies 70
Immunogenicity 71
Reproductive and developmental
toxicity 74
Species selec tion considerations 74
Studies for the assessment of
reproductive toxicity 76
Fertility and early emb ryonic
development (FEED): stages A
and B 77
Embryo-fetal development (EFD) and
enhanced pre- and post-natal
development (ePPND): stages C
and D and C through F 78
Genotoxicity and carcinogenicity 81
Genotoxicity 81
Carcinogenicity 81
CHAPTER
a
Retired.
57
Nonclinical Development of Biologics, Vaccines and
Specialty Biologics, Second Edition
https://doi.org/10.1016/B978-0-443-13344-2.00006-7
© 2025 Elsevier Inc. All rights are reserved, including those for text
and data mining, AI training, and similar technologies.
Special considerations for anticancer
drugs 84
First-in-human (FIH) clinical trial 86
Nonclinical safety program considerations 87
Dealing with the datadNOAEL
considerations 88
Translation of nonclinical data to
clinical trial dose selection 88
Summary 89
References 90
Further reading 93
Introduction
The development of recombinant DNA, large-scale cell culture technologies, and advances
in recombinant DNA and protein chemistry has resulted in the introduction of a wide range
of potential biopharmaceuticals, including cytokines, receptor agonists/antagonists, hor-
mones, growth factors, monoclonal antibodies, vaccines and gene therapy products for the
treatment of various diseases. A nonclinical safety program, whether it evaluates a conven-
tional new chemical entity (i.e., sm all molecular therapeutic) or a biopharmaceutical, should
provide relevant toxicological data that contributes to the overall safety assessment of that
new drug entity. The primary objectives of the nonclinical safety program are hazard identi-
fication and risk assessment. Hazard identification includes describing target organs and the
types of damage they may incur as a result of treatment in in vitro and in vivo models. Addi-
tionally, an understanding of possible reversibility and relationship of observed toxicities to
dose, route, and schedule of administration are important components of hazard character-
ization. Biomarkers that may correlate with the onset and/or severity of adverse effects
are also informative for describing hazards. The data from in silico, in vitro, and in vivo
studies, along with a deep understanding of target biology (e.g., downstream signaling,
expression profile, kinetics) and literature review to put the described hazards into context
(i.e., for a given dose, duration of treatment, indication, and patient population) form the ba-
sis of the risk assessment for any molecule. However, the complex structural and biological
characteristics of biotechnologically derived pharmaceuticals require different approaches to
their safety evaluation than for small molecules.
The goal of this chapter is to review the global regulatory guidelines and discuss imple-
mentation strategies for biological medicines; the focus is on ICH S6(R1) (ICH S6(R1)
2011), and includes growth factors, cytokines, protein hormones, and monoclonal antibodies
(i.e., those products that are currently regulated by the Center for Drug Evaluation and
Research (CDER)). Other products, such as gene therapy, stem cell therapies, vaccines
(DNA and viral), blood products, vitamins, antibiotics, and synthetic amino acids (<40 amino
acids), are outside the scope of this chapter.
Nonclinical safety assessment programs for biologics continue to embrace new technologies
and refine study design paradigms in order to reduce the use of animals (nonhuman primates
(NHP) in particular) (Sewell et al., 2016; Ackley et al., 2023; Hunter, 2023). The COVID
pandemic of the early 2020s highlighted an already limited NHP supply causing the sourcing
3. Regulatory guidelines and their application in the nonclinical evaluation of biological medicines58
I. Development of biopharmaceuticals
(especially of sexually mature animals) of the most often used species for biologics develop-
ment to become a global issue. Just as importantly, ethical concerns around the use of NHP
renewed calls for reduction and elimination of in vivo studies (Hunter, 2023). The FDA
Modernization Act of 2022, removed the requirement for all pharmaceuticals to be tested in
animals prior to first in human trials (United States, 2022). This change in law in the United
States reinforces the need for continual innovation in the nonclinical toxicology space by
embracing the potential for in vitro cell-based assays, microphysiological systems (commonly
called organ-on-a-chip), and computer modeling to replace animal studies (see also Chapter 4
on Early De-Risking). Throughout this chapter, the means by which a continued 3Rs (replace,
reduce, refine) focus is implemented into the regulatory strategy for biologics will be discussed.
In 1989 the World Health Organization (WHO) International Conference of Drug Regula-
tory Authorities (ICDRA) agreed that harmonized guidelines for pharmaceuticals were
needed. At the time it was considered that specific guidelines for biotherapeutics were pre-
mature and although there was support for a case-by-case approach for their development,
there was also concern that this approach could lead to different expectations between regu-
latory agencies and industry. Not long after the early ICH guidelines were agreed upon, the
rapid advances in science and technology, and accumulated experience (both from nonclin-
ical and clinical data) highlighted the different attributes of biotherapeutics and a proposal for
a separate guideline, Preclinical Safety Evaluation of Biotechnology-Derived Pharmaceuti-
cals, was approve d, and ICH S6 was adopted by the European, Japanese, and US health au-
thorities in 1997 (ICH, 2011; Terrell, 1994; Dayan, 1995; Zbinden, 1990a; Zbinden, 1990b;
Cavagnaro, 2008a; ICH Website).
Most of the early biopharmaceuticals upon which the first ICH S6 guidance was based
were recombinant proteins or hormones developed for replacement therapy (e.g., insulin,
growth hormone, and erythropoietin) or for life-threatening diseases such as leukemia
(e.g., interferons, interleukins). Because these recombinant proteins were analogs to their
endogenous counterparts, it was assumed that these “natural” protei ns would be relatively
nontoxic (Zbinden, 1990a; Zbinden, 1990b). The potential contaminants (degraded proteins,
residual DNA, pyrogens, microorganisms) related to the cell culture-based manufacturing
process caused greater concern among scientists than the potential toxicity of the therapeutic
protein itself (Rosenberg, 2004; Bailey-Kellog et al., 2014; Jawa et al., 2016; Gutierrez et al.,
2020; Jones et al., 2021). For proteins normally available systemically, which exhibited a nar-
row range of expected pharmacology, it was generally true. However, for proteins (e.g., cy-
tokines) which exhibited a broader range of biological effects, impacted multiple pathways,
and/or were not normally available systemically, the toxicity of the therapeutic protein itself
became central (Cavagnaro, 2008a; Dempster, 2000). In retrospect, it should not have been
surprising that these “natural” proteins produced unexpected activity when administered
parenterally. Early safety concerns regarding potential contaminants related to the
manufacturing process were largely alleviated by improvements in analytical techniques
(Dempster, 2000; Cosenza, 2008; Gutierrez et al., 2020; Jones et al., 2021).
These and other examples continued to emphasize the importance of understanding the
biology of therapeutic proteins. A review of the regulatory submissions (summary basis of
approval documents) for the early biopharmaceuticals (i.e., those registered in the 1980s)
showed that for a number of these, the nonclinical safety development strategy often
mirrored small molecular weight therapeutic development (i.e., included toxicity studies in
Introduction 59
I. Development of biopharmaceuticals
“traditional” rodent and nonrodent species). At the time, nonpharmacologically relevant an-
imal species were thought to aid evaluation of the potential for off-target toxicity or toxicity of
potential contaminants related to the manufacturing process. The relatively minor toxicity
observed in these studies was in sharp contrast to the high frequency of adverse related ef-
fects observed in subsequent human trials (Trown et al., 1986; Steinmann et al., 1993).
Although these programs included studies that would not be considered scientifically rele-
vant today, the data were helpful in that they emphasized that the primary toxicity for bio-
pharmaceuticals is exaggerated pharmacology and highlighted the importance of species
selection and of the case-by-case principles advocated by ICH S6.
All ICH guidelines are periodically reviewed, and with respect to ICH S6 a proposal to clarify
several topics was approved by the ICH Steering Committee. Nonclinical and clinical experience
that continued to accumulate, albeit with a slightly different set of products (i.e., monoclonal an-
tibodies), highlighted what appeared to be disharmony across various regulatory regions,
resulting in differences in the interpretation of the ICH S6 guideline. Because there was no major
philosophical change with respect to the case-by-case scientific approach to the nonclinical
development of biopharmaceuticals, it was decided that an addendum to the guideline was suf-
ficient. The revised guideline (ICH S6(R1)) was finalized in 2011 (ICH, 2011; Cosenza, 2008).
Although ICH S6(R1) is the primary international guideline for biopharmaceutical s, a
number of other guidelines refer to biopharmaceuticals in some aspect (Table 3.1). The orig-
inal ICH M3, which provided guidance for nonclinical safety studies needed to support hu-
man clinical trials, recognized that the established paradigms may not always be appropriate
or relevant to biopharmaceuticals and that their safety evaluation should follow ICH S6. In
practice, because ICH S6 was generally not as prescriptive, there was a tendency to default
to ICH M3. ICH M3(R2) has been clarified and now provides guidance rega rding the timing
of nonclinical studies relative to clinical development, not to the study designs (ICH, 2009).
There are, however, still a few areas of overlap between the two guidelines. For example,
combination toxicity testing is discussed in ICH M3(R2) but not in ICH S6(R1) and is most
likely due to greater experience with combination toxicity studies with small molecular
weight therapeutics. Both ICH M3(R2) and ICH S6(R1) (and ICH S9 and S9 Q&Afor
oncology biologics) will need to be consulted for a combination toxicity study with a
small-molecule therapeutic and a biopharmaceutical (ICH, 2009; ICH, 2011; ICH, 2010;
ICH, 2018). Given their different attributes, selection of the most appropriate species may
be complicated and needs to be carefully considered. In addition, ICH S6(R1) refers to ICH
M3(R2) for approaches to exploratory clinical trials.
Most of the safety guidelines mention biotherapeutics briefly, but ICH S9 and ICH S9 Q&A
(Nonclinical Evaluation of Anticancer Pharmaceuticals) cover both small molecules and bio-
logics (ICH, 2010; ICH, 2018). Other safety guidelines such as ICH S5(R2) (Development and
Reproductive Toxicity), ICH S7A (Safety Pharmacology), ICH S3A (Guidance for Toxicoki-
netics), and ICH S1A (Need for Carcinogenicity Studies) mention biopharmaceuticals as be-
ing within their scope but recognize that study designs or strategies may differ and/or may
need to be altered (ICH, 2020; ICH, 1994; ICH, 2000; ICH, 1995). In addition to the safety
guidelines, there are a number of quality guidelines that are either specific for bio-
pharmaceuticals (ICH 5A-Q5E) or refer to them ( Table 3.1). ICH Q11 (Development and
Manufacture of Drug Substances) refers to both small molecular weight therapeutics as
well as biopharmaceuticals.
3. Regulatory guidelines and their application in the nonclinical evaluation of biological medicines60
I. Development of biopharmaceuticals
Species selection
Species selection is a key activity initiated early in the drug development process for a bio-
pharmaceutical candidate. Selection of the relevant species forms the foundation for the
nonclinical toxicology program and associated regulatory strategy (Bussiere, 2008; Brennan
et al., 2015; Prior et al., 2020a; Prior et al., 2020b; Ackley et al., 2023). Because of its impor-
tance, the ICH S6(R1) guideline outlines in some detail regulatory expectations around
species selection. The most important principle is that any spe cies used in the in vivo nonclin-
ical toxicology studies should be pharmacologically relevant. A pharmacologically relevant
species is one that expresses the relevant binding epitope (target) of the drug and in which
biological (functio nal) activity of the biopharmaceutical can be demonstrated. Typically,
TABLE 3.1 Regulatory guidelines for nonclinical studies of biopharmaceutical candidates.
International guidelines
Safety (see current safety
guidelines at ICH official website:
ICH)
ICH S1AdNeed for carcinogenicity studies of pharmaceuticals
ICH S3AdNote for guidance on toxicokinetics: The assessment of systemic
exposure in toxicity studies
ICH S6(R1)dPreclinical safety evaluation of biotechnology-derived
pharmaceuticals
ICH S5(R3)dRevision of S5 guideline on detection of toxicity to reproduction
for human pharmaceuticals
ICH S7AdSafety pharmacology studies for human pharmaceuticals
ICH S9dNonclinical evaluation for anticancer pharmaceuticals
ICH S9 and S9 Q&A nonclinical evaluation for anticancer pharmaceuticals
ICH M3(R2)dGuidance on nonclinical safety studies for the conduct of human
clinical trials and marketing authorization for pharm
Aceuticals
Quality (see current quality
guidelines at ICH official web site:
ICH)
ICH Q1CdStability testing for new dosage formsdannex to the ICH
harmonised tripartite guideline on stability testing for new drugs and products
(November 1996)ICH Q5A(R1)dViral safety evaluation of biotechnology
products derived from cell lines of human or animal origin (september 1999)ICH
Q5BdQuality of biotechnological products: Analysis of the expression construct
in cells used for production of r-DNA derived protein products (November
1995)ICH Q5CdStability testing of biotechnology/Biological products
(November 1995)ICH Q5DdQuality of biotechnological products: Derivation
and characterization of cell substrates used for production of biotechnological/
Biological products (July 1997)ICH Q5EdComparability of biotechnological/
Biological products subject to changes in their manufacturing process
(November 2004)ICH Q6BdSpecifications: Test procedures and acceptance
criteria for biotechnological/Biological products (March 1999)ICH Q7dGood
manufacturing practice guide for active pharmaceutical ingredients (November
2000)ICH Q8dPharmaceutical development (august 2009)ICH Q9dQuality
risk management (November 2005)ICH Q10dPharmaceutical quality system
(June 2008)ICHQ11dDevelopment and manufacture of drug substances
(chemical entities and biotechnological/Biological entities) (step 4, May 2012)
ICH M4Q(R1)dCommon technical document (september 2002)
Species selection 61
I. Development of biopharmaceuticals
biological activity will be demonstrated in species-specific in vitro or ex vivo cell-based assays
and/or in vivo pharmacology or toxicology studies. ICH S6(R1) states that “Modulation of a
known biologic response or of a pharmacodynamic (PD) marker can provide evidence for
functional activity to support species relevance.” Hence, demonstration of pharmacological
relevance of the species utilized in the toxicology studies will be a regulatory expectation
for any biopharmaceutical.
Selecting a relevant species
Any animal species that can be used in nonclinical toxicology studies can be considered as
a possible relevant species. Species that are most frequently used include rodents such as
mice and rats, and nonrodents such as rabbits and nonhuman primates, typically the cyno-
molgus or less commonly rhesus monkey ( Sewell et al., 2016; Burm et al., 2014; Prior et al.,
2020a; Ackley et al., 2023). Other species that have been used successfully and are acceptable
to regulatory authorities include the hamster, woodchuck, dog, mini-pig, and other
nonhuman primates, including the common marmoset.
It is sometimes thought that the dog cannot be considered as the nonrodent species for bio-
pharmaceutical testing and that the default nonrodent species is the nonhuman primate. This
position is usually based on anecdotal evidence that hypersensitivity and/or immunogenicity
in the dog precludes its use as a relevant species. As with other species, including rodents and
nonhuman primates, immunogenicity can be successfully managed and this observation
alone does not preclude the use of the dog in toxicity studies. The dog has been successfully
used for toxicology programs supporting the registrat ion of small bioactive peptides,
including Cetrotide for fertility, and recombinant proteins including growth hormone and
the erythropoietins (FDA, 2018; Bader et al., 1992; Prahalada et al., 1998; Schwahn et al.,
2000). However, the dog has only rarely been used to support monoclonal antibody pro-
grams (Prior et al., 2020a, Prior et al., 2020b, Ackley et al., 2023). Anecdotal information sug-
gests that dogs are more prone to serious hyperse nsitivity reactions, including severe acute
anaphylactic-like reactions and/or immune complex-associated vasculitis when administered
monoclonal antibodies. These effect s can compromise the conduct of a toxicity study and/or
interpretation of toxicity data. Other considerations include the lack of reagents available for
endpoints like immunophenotyping, and difficulty of conducting developmental and repro-
ductive toxicity studies in the dog, because the immune system and FcRn receptor biology are
less well-characterized in the dog than in other nonclinical species such as the rodent and
nonhuman primate (Skaggs et al., 2019; Ackley et al., 2023).
Screening paradigms
In accordance with ICH S6(R1) a number of factors should be taken into consideration
when screening for relevant species. Several basic biology/pharmacology questions can be
asked at the start of the screening process to help guide species selection (Table 3.2) and Prior
et al. (Prior et al., 2020a, Prior et al., 2020b).
Practically, the approach taken to screen for relevant species can be tiered and usually
starts with cross-species comparisons of target amino acid sequence homology and relative
binding affinity and binding specificity of the biopharmaceutical to the target. Additional
3. Regulatory guidelines and their application in the nonclinical evaluation of biological medicines62
I. Development of biopharmaceuticals
data from mRNA expression databases and immunohistochemical data on target distribution
can also be gathered and may come from the literature, commercially available databases, or
in-house studies. Early analysis of these data sets helps to identify potentially relevant species
based on sequence (the genomic sequences for all the major nonclinical toxicology species are
available-for information see Krause et al.) and binding similarity (i.e., 90% identity is better
than 60%) and target tissue distribution in the nonclinical species versus human (Krause
et al., 2023; Ackley et al., 2023).
This work alone is not sufficient to demonstrate that a nonclinical species is pharmacolog-
ically relevant; additio nal in vitro and/or in vivo data will be necessary to demonstrate phar-
macological relevance. ICH S6(R1) highlights that functional activity can be demonstrated in
species-specific cell-based systems and/or in vivo pharmacology or toxicology studies. Phar-
macological activity can also be confirmed using PD markers, if they are available. The PD
marker may or may not be an endpoint that is translatable to the clinical setting or even a
desired effect. A toxicity finding such as microscopic morphologic changes in a tissue that
can be linked to the mechanism of action could serve as a relevant biomarker. In some cases,
in vivo biomarkers of pharmacologic activity cannot be identified and species-specific
cell-based assays measuring some aspect of functional activity related to binding of the bio-
pharmaceutical to the target may be the only available measure of pharmacology. It is also
important to assess the relative binding affinity and/or pharmacologic activity in potential
nonclinical species versus human. Pharmacologic activity, if diminished, must be robust
enough in the selected species to ensure that potential toxicities can be identified during
the conduct of the toxicity studies.
The screening process is also important to help justify when a species is not relevant. It is
the expectation of health authorities that the appropriate scientific justification be provided if
a single-species program (i.e., nonhuman primate only) is being proposed or if rodents and/
or rabbits are being excluded from developmental and reproductive toxicity testing. At a
minimum, lack of binding of the biopharmaceutical to the species target should be demon-
strated and if some binding does occur, but with lower affinity, additional work may be
required to show that there is minimal or no pharmacologic activity. Determining how
much relative pharmacologic activity is enough to proceed with a species can be difficult.
If the pharmacologic activity can be increased by higher dose levels or more frequent dosing
so that potential toxicity could be assessed , then it may be an expectation to use this species in
the nonclinical testing program. Immunogenicity (formation of antidrug antibodies to the
TABLE 3.2 Species selection for toxicology studies with biopharmaceuticals.
Questions to consider when selecting a pharmacologically relevant species
1. How novel is the target? Are there other programs and what species did they use?
2. How well is the target conserved across species?
3. Is the target expressed in animal species?
(a) Does the target have a similar role as the human target?
(b) Are the downstream pharmacological effects after target engagement similar to human?
(c) Is the target expressed on similar tissues/cells in animals and humans?
4. Is the potency of any pharmacological effects similar in animals and humans?
Species selection 63
I. Development of biopharmaceuticals
biopharmaceutical) is sometimes used as a rationale to not use a species, usually the rodent,
in the nonclinical program. Immunogenicity can be managed in a variety of ways (e.g.,
increasing the frequency of dosing, using higher dose levels and/or increasing the number
of animals per dosing group). It will be expected that when immunogenicity can be managed
so that adequate numbers of animals maintain some level of exposure throughout the dura-
tion of testing that these species still be considered relevant.
In some cases, the target epitope may not be expressed excep t under disease conditions or
expressed at very low levels in normal healthy animals (e.g., cancer cell antigens). If the target
is expressed at low levels in the nonclinical species there is still an expectation that nonclinical
toxicity studies will be conducted. The biopharmaceutical can be tested in normal animals
expressing low levels of the target and this is acceptable to most health authorities. Al terna-
tive models, such as disease models, can also be considered to either supplement or replace
the use of normal animals, if scientifically justified. In addition, other in vitro models may
provide useful data with respect to expected pharmacology and potential safet y issues which
could influence whether a biopharmaceutical should be progressed into in vivo studies (see
also Chapter 4 on Early De-Risking).
The results from toxicity studies in nonrelevant animal species may be misleading and are
strongly discouraged in the ICH S6(R1) guideline. There is no requirement by health author-
ities to conduct toxicity studies in two species in this case. For example, if the rat was not a
pharmacologically relevant species and the nonhuman primate was, the nonclinical program
would be conducted in nonhuman primate only.
Use of tissue cross-reactivity assays
One assay that has sometimes been used to justify species selection is the tissue cross-
reactivity (TCR) assay. TCR assay results are required by health authorities to be submitted
for monoclonal antibodies or other molecules that contain a complementarity determining re-
gion (CDR) and, with some exceptions for low target knowledge, are not intended for the
treatment of advanced cancer (see Chapter 13 Biological Therapies for Cancer and ICH S9
Q&A Section 2.6) as part of the initial IND (Investigational New Drug) application. TCR as-
says are primarily used to determine if there is any unexpected or off-target binding of the
biopharmaceutical when screened against an extensive panel of human and/or animal
tissues (Leach et al., 2010; MacLachlan et al., 2021). In the ICH S6(R1) addendum it is empha-
sized that this assay is of limited value for species selecti on and should not be used as a
primary selection criterion. TCR studies only determine binding to target antigen and do
not confirm that the biopharmaceutical is pharmacologically active in the species being
assessed. Tissue cross-reactivity studies can be used to support species selection by supple-
menting knowledge of tissue distribution and showing similarity of binding of the
biopharmaceutical in human and animal tissues.
There are other considerations when conducting tissue cross-reactivity assays beyond
those related to their potential utility for species selection. In general, tissue cross-reactivity
studies using a full panel of animal tissues are not recommended. When there is unexpected
binding in human tissues, supplemental information from selected animal tissues may be
helpful to understand correlations with any findings observed in the toxicity studies. In
some cases, the clinical candidate does not make a good immunohistochemistry reagent
3. Regulatory guidelines and their application in the nonclinical evaluation of biological medicines64
I. Development of biopharmaceuticals
and the assay may not be technically feasible; in these cases, a tissue cross-reactivity study
does not have to be conducted. Experiments showing that the clinical candidate does not
bind appropriate positive control frozen or formalin-fixed tissues and/or background stain-
ing issues make the studies uninterpretable will usually suffice as justification in the dossier.
When the biopharmaceutical is a bispecific molecule (i.e., binds to two targets) the entire
molecule can be tested in a tissue cross-reactivity study; each binding component does not
have to be tested individually. The testing of a homologous protein in a tissue cross-
reactivity study is not recommended and does not add value since the clinical candidate
will have been tested on a full panel of human tissues.
When a relevant species cannot be identified?
When a pharmacologically relevant species cannot be ide ntified, other options can be
considered including the use of alternative models, or in some specific cases, short-term
testing in a nonrelevant species. There is a st rong expectation by health authorities that
in vivo toxicity testing will be conducted and the sponsor will need to scientifically justify
alternative types and durations of studies in the nonclinical toxicology program. Alternative
models include the use of homologous proteins, transgenic animals, and disease models (Bus-
siere et al., 2009). All of these models can have utility; however, rigorous evaluation of the
potential caveats should be conducted and these models should only be considered if, after
thorough screening, a relevant standard test species cannot be identified (Table 3.3).
The most common alternative approach is to develop a species-specific homologous mole-
cule (e.g., monoclonal antibody or recombinant protein) that binds to the same pharmaco-
logic target as the clinical candidate in an animal model. There is much to consider when
developing a homologous protein for use in a nonclinical toxicology program; several of
the pros and cons are discussed by Bussiere et al. (Bussiere et al., 2009). Homologous proteins
can be used for hazard assessment and understanding the potential for adverse effects, but
cannot be used for quantitative risk assessment. There is still a preference by many companies
and some health authorities to use the clinical candidate rather than a homologous protein in
the nonclinical toxicity program whenever feasible. The use of homologous proteins in devel-
opmental and reproductive toxicity studies is also discouraged unless there is a strong scien-
tific rationale. There is no regulatory expectation (or precedent) for the use of homologous
proteins in short- or long-term carcinogenicity studies.
TABLE 3.3 Using alternative models to support a nonclinical safety package.
Before using an alternative approach consider the following:
1. Determine if anticipated benefits substantially outweigh the risks
2. Establish a clearly defined scientific rationale/justification for using the model
3. Determine if the model will substitute for or complement studies in normal animals
4. Understand impact of poorly understood safety findings on development of compound/target
5. Ensure that endpoints are clearly defined and that associated tests are validated in that species/model
6. Determine if data would be better collected from ef ficacy studies
Species selection 65
I. Development of biopharmaceuticals
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