Nonclinical Evaluation of the Immunotoxic Potential of Pharmaceuticals

Administrative guidance, not enacted legislation. This captured publisher edition preserves the listed document and attachments; later developments are not independently consolidated.

Nonclinical Evaluation of
the Immunotoxic Potential
of Pharmaceuticals
Guidance for Industry
U.S. Department of Health and Human Services
Food and Drug Administration
Center for Drug Evaluation and Research (CDER)
June 2023
Pharmacology/Toxicology

Nonclinical Evaluation of
the Immunotoxic Potential
of Pharmaceuticals
Guidance for Industry
Additional copies are available from:
Office of Communications, Division of Drug Information
Center for Drug Evaluation and Research
Food and Drug Administration
10001 New Hampshire Ave., Hillandale Bldg., 4th Floor
Silver Spring, MD 20993-0002
Phone: 855-543-3784 or 301-796-3400; Fax: 301-431-6353
Email: druginfo@fda.hhs.gov
https://www.fda.gov/drugs/guidance-compliance-regulatory-information/guidances-drugs
U.S. Department of Health and Human Services
Food and Drug Administration
Center for Drug Evaluation and Research (CDER)
June 2023
Pharmacology/Toxicology

Contains Nonbinding Recommendations
TABLE OF CONTENTS
I. 	INTRODUCTION ............................................................................................................. 1
II. 	BACKGROUND ................................................................................................................ 1
III. 	ASSESSING THE POTENTIAL TO SUPPRESS IMMUNE SYSTEM ACTIVITY 3
A. 	General Immunosuppression Assessment ................................................................................... 3
B. 	Immunosuppression and Carcinogenicity ................................................................................... 3
C. 	Immunosuppression and Opportunistic Infections .................................................................... 4
VI. 	ASSESSING THE POTENTIAL TO INCREASE IMMUNE SYSTEM ACTIVITY 5
A. 	Immunostimulation ....................................................................................................................... 5
B. 	Dermal Sensitization...................................................................................................................... 7
C. 	Systemic Hypersensitivity-Based Reactions ................................................................................ 8
V. 	ASSESSING ADVERSE EFFECTS ON IMPLANTATION AND PREGNANCY .... 8
VI. 	ASSESSING DEVELOPMENTAL IMMUNOTOXICITY .......................................... 9
VII. 	RISK ASSESSMENT ........................................................................................................ 9
VIII. 	ADMINISTRATIVE CONSIDERATIONS .................................................................. 10
REFERENCES ............................................................................................................................ 11

Contains Nonbinding Recommendations
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Nonclinical Evaluation of the Immunotoxic
Potential of Pharmaceuticals
Guidance for Industry1
This guidance represents the current thinking of the Food and Drug Administration (FDA or
Agency) on this topic. It does not establish any rights for any person and is not binding on FDA
or the public. You can use an alternative approach if it satisfies the requirements of the
applicable statutes and regulations. To discuss an alternative approach, contact the FDA office
responsible for this guidance as listed on the title page.
I. 	INTRODUCTION
The purpose of this guidance is to assist sponsors in the nonclinical evaluation of the
immunotoxic potential of pharmaceuticals. Immunotoxicity is, for the purposes of this guidance,
defined as unintended immunosuppression or stimulation (including hypersensitivity), which can
include adverse effects of exaggerated pharmacology of pharmaceuticals that are intended to act
as immunomodulators.2 This guidance applies to drug products, including small molecule drugs
and oligonucleotides, as well as certain biological products such as biotechnology-derived
therapeutic proteins (referred to herein as biopharmaceuticals). For the purposes of this
guidance, the term pharmaceutical will be used as a general term that encompasses all of these
product types. Cell and gene therapies, adjuvanted vaccines, and blood products are not within
the scope of this guidance.
In general, FDA’s guidance documents do not establish legally enforceable responsibilities.
Instead, guidances describe the Agency’s current thinking on a topic and should be viewed only
as recommendations, unless specific regulatory or statutory requirements are cited. The use of
the word should in Agency guidances means that something is suggested or recommended, but
not required.
II. 	BACKGROUND
The immune system is a complex and tightly regulated system that involves multiple biological
components (e.g., circulating peptides, proteins and cells, tissue-resident cells, as well as
1 This guidance has been prepared by the Office of New Drugs in the Center for Drug Evaluation and Research at
the Food and Drug Administration.
2 For the purposes of this guidance, an immunomodulator is a pharmaceutical that is intended to alter the
performance of a discrete component of the immune system to either stimulate or suppress specific immune system
activities.

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specific tissues and organs distributed throughout the body) and mediates complex
physiological responses, with the primary purpose of protecting the body from infections,
tumors, and foreign substances. Perturbations of the function of the immune system have the
potential to result in adverse consequences—immunotoxicity—which can in some cases be
severe. Therefore, an assessment of the ability of pharmaceuticals to adversely affect the
activity of the immune system is an essential component of evaluating the safety of
pharmaceuticals.
There are internationally harmonized guidances that provide recommendations related to the
assessment of immunotoxicity risk. The primary guidances concerning immunotoxicity
assessment of small molecule drugs and biopharmaceuticals are the ICH guidances for industry
S8 Immunotoxicity Studies for Human Pharmaceuticals (April 2006)3 and S6(R1) Preclinical
Safety Evaluation of Biotechnology-Derived Pharmaceuticals (May 2012). The guiding principle
of both guidances is that the assessment of immunotoxic potential relies primarily upon
integration of the findings of the general toxicity studies in combination with other data, such as
(1) pharmacological properties of the pharmaceutical, (2) intended patient population, (3)
structural similarities to compounds known to affect the immune system, (4) pharmaceutical
disposition, (5) and findings in clinical studies. For immunomodulators, the role of the intended
target in immune function should also be considered. When this first-tier assessment identifies a
potential immunotoxicity hazard, more specific assessments of immune function may be
warranted to further characterize the risk to human subjects and patients.
In addition to these aforementioned ICH guidances, FDA maintained guidance for
investigational new drugs that was published as final guidance in 2002.4 The guidance provided
immunotoxicity guidance that was outside of the scope of ICH S8 (e.g., hypersenstitivity,
adverse immunostimulation). This present guidance expands upon the previously withdrawn
2002 guidance by broadening the scope to also include pharmaceuticals intended to affect the
immune system, biopharmaceuticals, and oligonucleotides. Expanded guidance is also provided
for assessing the carcinogenicity risk of immunomodulators, methods to assess the risk for
adverse immunostimulation (e.g., cytokine release assays), nonanimal methods for assessing
dermal sensitization, approaches for assessing the effects of immunotoxicants on pregnancy, and
developmental immunotoxicity.
This guidance finalizes the draft guidance for industry Nonclinical Safety Evaluation of the
Immunotoxic Potential of Drugs and Biologics (February 2020).5
3 We update guidances periodically. For the most recent version of a guidance, check the FDA guidance web page at
https://www.fda.gov/regulatory-information/search-fda-guidance-documents.
4 See the guidance for industry Immunotoxicology Evaluation of Investigational New Drugs (October 2002)—
withdrawn.
5 When final, this guidance will represent the FDA’s current thinking on this topic. For the most recent version of a
guidance, check the FDA guidance web page at https://www.fda.gov/regulatory-information/search-fda-guidance-
documents.

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For product-specific recommendations related to this guidance, FDA recommends that sponsors
contact the appropriate review division.6
III. 	ASSESSING THE POTENTIAL TO SUPPRESS IMMUNE SYSTEM ACTIVITY
A. 	General Immunosuppression Assessment
As noted above, internationally harmonized guidance regarding nonclinical immunotoxicity
assessment of small molecule drugs and biopharmaceuticals is provided by ICH S8 and ICH
S6(R1), respectively. The following concepts for the assessment of immunosuppression risk
should be considered in conjunction with these guidances.
For pharmaceuticals (including biopharmaceuticals) that are intended to act via a suppressive
immunomodulatory mechanism of action (MoA), sponsors should fully assess the known
immunobiology of the intended mode of action as it relates to the potential for adverse
consequences of exaggerated pharmacology. For less well-characterized immune targets, this
assessment may warrant one or more dedicated nonclinical studies7 to better inform the risk of
exaggerated target engagement. In addition, dedicated assays may be warranted to characterize
the effects of the pharmaceutical on other related immune functions. The specifics of on- and off-
target assay selection should be dictated by the intended MoA of the pharmaceutical along with
scientific evaluation of how the intended immune suppression may affect related activities of the
immune system.
For biopharmaceuticals that are not intended to affect the immune system, sponsors may
consider performing an integrated evaluation of the potential for unintended immunosuppression.
This evaluation could be similar in principle to the weight-of-evidence (WoE) evaluation as
described in ICH S8. Whether any additional studies are warranted would be guided by the
findings of the integrated evaluation.
For small molecule drugs that act via an antiproliferative MoA, such as those used to treat
cancer, follow-up assays such as those discussed in ICH S8 are generally not warranted.
B. 	Immunosuppression and Carcinogenicity
Immunosuppression has the potential to increase the risk of certain tumor types in humans,
depending on which components of the immune system are suppressed and to what extent.
Tumors arising from immunosuppression are primarily associated with loss of control of
chronic/latent pathogen infections, although direct interference with tumor surveillance could
6 See the draft guidance for industry Formal Meetings Between the FDA and Sponsors or Applicants of PDUFA
Products (December 2017). When final, this guidance will represent the FDA’s current thinking on this topic.
7 FDA supports the principles of the 3Rs (replace/reduce/refine) for animal use in testing when feasible. FDA
encourages sponsors to consult with review divisions when considering a nonanimal testing method believed to be
suitable, adequate, and feasible. FDA will consider whether the alternative method is adequate to meet the
nonclinical regulatory need.

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also result in an increased risk for tumors. As such, sponsors should consider the effects of a
drug on the immune system when assessing its carcinogenic potential.
Sponsors should follow the recommendations in the ICH guidances for industry S1A The Need
for Long-term Rodent Carcinogenicity Studies of Pharmaceuticals (March 1996), ICH S6(R1),
S9 Nonclinical Evaluation for Anticancer Pharmaceuticals (March 2010), and S9 Nonclinical
Evaluation for Anticancer Pharmaceuticals—Questions and Answers (June 2018) regarding the
need for a carcinogenicity assessment as well as which experimental approaches may be
warranted. To date, animal models, including rodent carcinogenicity studies, have been shown
to be of limited help in identifying an increased cancer risk that may arise in patients as a
consequence of immunosuppression. This is particularly true when the increased tumor risk is
caused by recrudescence of latent viral oncogenes, infectious agents, or chronic inflammatory
states, for which significant species differences exist that make clinical translatability
challenging. For small molecule drugs for which an increased risk of carcinogenicity is
anticipated as a result of profound drug-induced immunosuppression (e.g., antirejection
pharmaceuticals), a written, WoE-based risk assessment may be adequate to assess
carcinogenicity risk. A WoE-based risk assessment is also particularly relevant for
pharmaceuticals that lack the intended pharmacological activity in rodents and/or when standard
carcinogenicity studies in rodents are not technically feasible. A WoE-based risk assessment
may also be adequate for most immunomodulatory biopharmaceuticals.
This WoE-based risk assessment should address relevant attributes of the drug and drug
target(s), including an evaluation of the impact on immune cell subpopulations and the potential
for a drug to increase tumor promotion, growth, and metastasis, with an emphasis on clinical
translatability. The effects of the pharmaceutical on key immune components thought to be
involved in tumor surveillance (e.g., natural killer cells, T cells, antigen-presenting cells), such
as downregulation or functional impairment of key immune cell populations, should be
considered. For small molecule drug products in particular, the WoE-based risk assessment
should also address the carcinogenic relevance of any compound-specific toxicology findings
not related to the product’s intended effect on the immune system (e.g., off-target activity).
For small molecule drugs that act through a more targeted modulation of the immune system,
such that profound immunosuppression is unlikely, the conduct of one or more rodent
carcinogenicity studies may be warranted.8
FDA recommends that sponsors discuss their proposed approach for assessing carcinogenic
potential of their product with the appropriate review division.
C. 	Immunosuppression and Opportunistic Infections
Profound immunosuppression is known to increase the risk of opportunistic infections, which
are typically associated with a wide range of bacteria, viruses, fungi, and parasites. The standard
general toxicology studies are not designed to be able to reliably predict the risk of these
8 See the ICH draft guidance for industry S1B(R1) Addendum to S1B Testing for Carcinogenicity of
Pharmaceuticals (November 2022). When final, this guidance will represent the FDA’s current thinking on this
topic.

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infections occurring in humans. If the WoE review suggests a cause for concern, then an
appropriately focused host resistance model, which may provide additional insight, could be
considered. The design of such a study, and whether it is warranted, should be discussed with
the appropriate review division. Regardless, the risk of opportunistic infections in humans as a
result of drug-induced immunosuppression should be evaluated clinically.
VI. 	ASSESSING THE POTENTIAL TO INCREASE IMMUNE SYSTEM ACTIVITY
A. 	Immunostimulation
Assessment of the risks associated with a heightened immune response normally requires a
safety evaluation paradigm that differs from that of immunosuppression, and may use specific
assays or alternative methodologies for translation to first-in-human trials.
Except where indicated, immunostimulatory pharmaceuticals are defined in this section as
products that are intended to either directly stimulate signaling in an immune cell subtype or
indirectly enhance the immune system response by blocking or activating an endogenous
regulator of the immune system response.
Toxicities of these products are often the result of exaggerated pharmacological activity but
may also be caused by expression of the target receptor in untargeted immune cell
subpopulations or tissues. It is therefore important to understand the MoA of the
pharmaceutical when determining which assays are most appropriate to evaluate the potential
hazards. For example, assays used when evaluating the immunotoxicity of T cell-engaging
(direct activation) molecules would be different from assays used when evaluating checkpoint
inhibitors or receptor agonists. The MoA, cellular distribution of the molecule, and potential to
induce direct immunostimulation in key cell types (e.g., T cells, dendritic cells) should guide
the approach to assay selection.
The following are examples of immunostimulatory effects:
• 	Excessive release of cytokines that can cause severe adverse reactions9 as shown by
the near-fatal clinical responses to the monoclonal antibody TGN1412 (Duff 2006). It
should be noted that the intended MoA of TGN1412 was immunosuppression through
activation of regulatory T cells, but its administration resulted in strong
immunostimulation of effector memory T cells. There are now commonly used in vitro
models available to evaluate the potential for this hazard (Bugelski et al. 2009; Finco et
al. 2014; Grimaldi et al. 2016).
• 	General immune activation of T cells, T regulatory cells, or antigen-presenting cells
caused by checkpoint inhibitor engagement resulting in immune-mediated tissue damage
in nontarget organs.
9 See guidance for industry Immunogenicity Assessment for Therapeutic Protein Products (August 2014).

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• 	Rapid, generalized depletion of target cells via immune clearance mechanisms resulting
in generalized immune activation (with or without cytokine release) as can be observed
with rapid Fc receptor–based clearance.
• 	Activation of pathogen-associated molecular pattern receptors (e.g., toll-like receptors)
and/or complement by oligonucleotides.
Below are examples of assays that may be considered for the evaluation of these types of
hazards. This list is not intended to be all-inclusive, as new assays and technologies are
constantly emerging and evolving. Sponsors should use the criteria defined above to determine
which assays will best identify the hazards associated with their molecule and what dosing and
monitoring will be most appropriate for the first-in-human clinical trial. All assays should
include appropriate positive and negative controls and have clear, measurable outcomes.
Information should be provided to support that the conducted assay(s) is fit-for-purpose (e.g.,
validation study results, literature citation).
• 	Cytokine release assay — Standard assays to date include use of soluble and immobilized
formats using peripheral blood mononuclear cells, whole blood, and other matrices. Other
formats that may be considered include endothelial cell/peripheral blood mononuclear
cell co-culture assay, tumor and endothelial cell co-cultures, and use of patient-derived
cells.
• 	Complement-dependent cytotoxicity/antibody-dependent cell-mediated cytotoxicity
assays — Complement-dependent cytotoxicity and antibody-dependent cell-mediated
cytotoxicity assays evaluate cytolytic processes using either complement or antibody-
dependent interactions for cell lysis to occur.
• 	Complement activation assays — Measurement of the levels in serum of activated
complement fragments (C3a, C5a) and/or the Bb split product.
• 	Proliferation/activation assays — Many assays exist to assess proliferation, including
carboxyfluorescein succinimidyl ester (CFSE) proliferation assay, 5-bromo-2’-
deoxyuridine incorporation assay, flow cytometric assessment of activation markers, and
the enzyme-linked immune absorbent spot (ELISpot) assay, among others. Such assays
will evaluate the ability of T cells to activate and proliferate and in some cases assess
innate immune activation of antigen-presenting cells.
• 	Other assays — Assays typically used to assess vaccine effectiveness or cellular
proliferation such as MIMIC (minimal methylation classifier) and other new technologies
can be considered depending on the molecule being evaluated. Novel methods, including
microphysiological systems or immune-humanized mice, may also be options depending
on the validation of these techniques.
If a product has already demonstrated a clear potential to directly cause cytokine release (e.g., a
CD3 bispecific T cell redirector) or induce other forms of immune activation, then additional

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assays may not be necessary, as the hazard has already been identified. Similarly, if one assay is
positive, then an assay in another format may not be warranted.
Although a positive response in a cytokine release assay may not preclude further development
of a drug, depending on the indication, magnitude/duration of the effect, and/or the number and
functions of cytokines affected, it may impact the selection of the appropriate starting dose and
inform clinical monitoring, the need for potential interventions, and dose escalation and
stopping criteria.
For biopharmaceuticals intended to stimulate an immune response either directly or indirectly, a
starting dose based on a minimal anticipated biologic effect level or a pharmacologically active
dose may be more appropriate than a starting dose based on toxicology endpoints, such as the
no-observed-adverse-effect level. The same approach may apply to drug products intended to
stimulate specific immune system outcomes, depending on the relevance of available animal
models.
The above approaches may also be suitable for assessing the immunotoxicity risk of products
whose intended pharmacology does not involve immune cell activation but nonetheless are
expected to activate components of the immune system (e.g., oligonucleotides).
B. 	Dermal Sensitization
Topical pharmaceuticals should be assessed for their dermal sensitization potential. Dermal
sensitization is an immune response to a previously encountered chemical or substance that
results in an inflammatory dermal reaction upon reexposure. As an assessment of skin
sensitization for individual chemicals, FDA will consider a battery of studies (e.g., in silico, in
chemico, in vitro) that have been shown to adequately predict human skin sensitization with an
accuracy similar to existing in vivo methods. Several in chemico and in vitro assays for skin
sensitization and defined approaches for combining data are described in the Organisation for
Economic Co-operation and Development (OECD) test guidelines.10 Additionally, FDA also
currently accepts the guinea pig maximization test using the clinical formulation to assess the
sensitization potential of a topical drug product. FDA will also accept the murine local lymph
node assay but no longer recommends this assay because of its technical limitations (Basketter
and Kimber 2011).
10 See OECD (2021), Test No. 442C: In Chemico Skin Sensitisation: Assays addressing the Adverse Outcome
Pathway key event on covalent binding to proteins, OECD Guidelines for the Testing of Chemicals, Section 4, OECD
Publishing, Paris, https://doi.org/10.1787/9789264229709-en; OECD (2018), Test No. 442D: In Vitro Skin
Sensitisation: ARE-Nrf2 Luciferase Test Method, OECD Guidelines for the Testing of Chemicals, Section 4, OECD
Publishing, Paris, https://doi.org/10.1787/9789264229822-en; OECD (2018), Test No. 442E: In Vitro Skin
Sensitisation: In Vitro Skin Sensitisation assays addressing the Key Event on activation of dendritic cells on the
Adverse Outcome Pathway for Skin Sensitisation, OECD Guidelines for the Testing of Chemicals, Section 4, OECD
Publishing, Paris, https://doi.org/10.1787/9789264264359-en; OECD (2021), Guideline No. 497: Defined
Approaches on Skin Sensitisation, OECD Guidelines for the Testing of Chemicals, Section 4, OECD Publishing,
Paris, https://doi.org/10.1787/b92879a4-en.

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For topical pharmaceuticals, data from the dermal sensitization assessment should be submitted
at the time of investigational new drug application submission.
C. 	Systemic Hypersensitivity-Based Reactions
Systemic hypersensitivity reactions are significant potential pharmaceutical-induced adverse
reactions. To date, however, there are no standard nonclinical assays to adequately evaluate the
potential risks. Fit-for-purpose assays and/or a WoE assessment may be considered as long as
they are appropriate and scientifically justified. For example, for drug-induced anaphylactoid
reactions, in vitro assays such as complement activation or mast cell/basophil activation assays
may have value in assessing risk. FDA recommends that sponsors discuss their proposed
approaches for assessing systemic hypersensitivity risk, and whether such studies are warranted,
with the appropriate review division.
V. 	ASSESSING ADVERSE EFFECTS ON IMPLANTATION AND PREGNANCY
Pharmaceuticals that affect the maternal immune system have the potential to adversely affect
implantation of the embryo, fetal development, and the ability to maintain the pregnancy.
For pharmaceuticals that are not intended to affect the immune system, the risk for adverse
effects on the maternal immune system that can affect implantation and gestation would typically
be identified in the fertility and early embryonic development and/or embryo-fetal development
studies conducted on most pharmaceuticals.11 These studies would generally be considered
adequate for assessing this risk.
Similarly, for pharmaceuticals that are intended to affect the immune system, fertility and early
embryonic development and embryo-fetal development studies may have utility in characterizing
the risk for adverse effects on the maternal immune system that can affect implantation and
gestation. However, if the MoA of a pharmaceutical is known to be incompatible with fertility or
maintenance of pregnancy, it may be appropriate to assess the risk based on a WoE
approach.12,13
Fertility and early embryonic development studies are not generally warranted for
pharmaceuticals intended to treat patients with advanced cancer.14
11 See the ICH guidance for industry S5(R3) Detection of Reproductive and Developmental Toxicity for Human
Pharmaceuticals (May 2021).
12 Ibid.
13 See the guidance for industry Oncology Pharmaceuticals: Reproductive Toxicity Testing and Labeling
Recommendations (May 2019).
14 See ICH S9.

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VI. 	ASSESSING DEVELOPMENTAL IMMUNOTOXICITY
Pharmaceuticals that have no appreciable adverse effect on the mature immune system
nonetheless have the potential to adversely affect the developing immune system. Given the
extended period over which the immune system develops, the immune system can be sensitive
to adverse effects of pharmaceuticals throughout the fetal, neonatal, and juvenile stages of
development.
As with the assessment of immunotoxicity of the mature immune system, an evaluation of the
potential of a pharmaceutical to adversely affect the developing immune system relies on a
WoE integration of multiple factors, as described in ICH S8.
If there is a concern that immune system development could be adversely affected by a
pharmaceutical, and the existing data do not adequately characterize the risk to the exposed
subject (pediatric patient or in utero or lactationally exposed infant), then sponsors should
provide additional data to characterize this risk. As recommended in the ICH guidance for
industry S11 Nonclinical Safety Testing in Support of Development of Pediatric
Pharmaceuticals (May 2021), this can include the evaluation of immunotoxicology endpoints
in the offspring of treated dams in otherwise warranted developmental toxicology studies (i.e.,
pre- and postnatal development (PPND) study or enhanced PPND (ePPND) study) if adequate
exposure to the pharmaceutical is demonstrated in the offspring. A juvenile animal study in
which juveniles are directly exposed to the pharmaceutical may be warranted if the
PPND/ePPND study is unable to adequately characterize the risk. Juvenile and PPND/ePPND
studies are generally not warranted for pharmaceuticals intended to treat patients with advanced
cancer.
Should a study be warranted to assess the risk of developmental immunotoxicity, the test
species should be appropriate for the endpoints being assessed. The endpoints to be included
should be scientifically justified and appropriate for assessing the concern, and could include
enumeration of specific immune cell populations (immunophenotyping), the function of the
immune system and its components, and/or the anatomical integrity of the immune system. As
there are differences in the timing of immune system developmental landmarks across species
(Skaggs et al. 2019), sponsors should ensure that the dosing interval covers the intended
developmental period.
To avoid the potentially unwarranted use of animals, sponsors should consult with the
appropriate review division before conducting ePPND or juvenile animal studies, particularly if
the studies are being conducted solely for assessing developmental immunotoxicity risk.
VII. 	RISK ASSESSMENT
There is limited understanding of the extent of reduced (or increased) immune function required
to have a significant biological effect in humans (e.g., increased risk of infection, tumor
development, or autoimmunity). A WoE approach where all immunotoxicity data are
considered as a whole (e.g., consideration of the MoA of the drug, the translatability of

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nonclinical findings, the predicted extent and duration of human exposure, the clinical
population, disease status, concomitant medication, etc.) is recommended when interpreting the
findings of immunotoxicity assays and when considering the risk of clinically significant
immunotoxicity occurring in humans.
VIII. 	ADMINISTRATIVE CONSIDERATIONS
Sponsors should, to the extent practicable, follow existing guidance on placing
immunotoxicology studies in the electronic common technical document (eCTD) format.15
Stand-alone immunotoxicology studies should be included in the eCTD in section 4.2.3.7.2,
with the exception of stand-alone assessments of antigenicity (allergenicity), which should be
included in section 4.2.3.7.1. WoE assessments of immunotoxicology should be submitted to
eCTD section 4.2.3.7.2. Data evaluating the immune system, which are part of a general repeat-
dose toxicity study, including immunogenicity (antidrug antibody formation) data, should be
included with the repeat-dose toxicity study in section 4.2.3.2. Please refer to the FDA eCTD
technical specification The Comprehensive Table of Contents Headings and Hierarchy16 for
further details.
15 See the ICH guidance for industry M2 eCTD: Electronic Common Technical Document Specification (April
2003).
16 Accessible at https://www.fda.gov/downloads/drugs/ucm163175.pdf.

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REFERENCES	1
2
Basketter, DA and I Kimber, 2011, Skin Irritation, False Positives and the Local Lymph Node	3
Assay: A Guideline Issue? Regul Toxicol Pharmacol, 61(1):137–140.	4
5
Bugelski, PJ, R Achuthanandam, RJ Capocasale, G Treacy, and E Bouman-Thio, 2009,	6
Monoclonal Antibody-Induced Cytokine-Release Syndrome, Expert Rev Clin Immunol, 5(5):	7
499–521.	8
9
Duff, GW, Expert Scientific Group on Phase One Clinical Trials, 2006, available at	10
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13
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Schneider, A Ibraghimov, S Scesney, D Serna, R Prell, R Stebbings, and PK Narayanan, 2014,	15
Cytokine Release Assays: Current Practices and Future Directions, Cytokine, 6(2):143–155.	16
17
Grimaldi, C, D Finco, MM Fort, D Gliddon, K Harper, WS Helms, JA Mitchell, R O’Lone, ST	18
Parish, M-S Piche, DM Reed, G Reichmann, PC Ryan, R Stebbings, and M Walker, Cytokine	19
Release: A Workshop Proceedings on the State-of-the-Science, Current Challenges and Future	20
Directions, 2016, Cytokine, 85, 101–108.	21
22
Skaggs, H, GJ Chellman, M Collinge, B Enright, CL Fuller, J Krayer, L Sivaraman, and GF	23
Weinbauer, 2019, Comparison of Immune System Development in Nonclinical Species and	24
Humans: Closing Information Gaps for Immunotoxicity Testing and Human Translatability,	25
Reproductive Toxicology, 89:178–188.	26
27