Guidance for Industry

S7A Safety Pharmacology

Studies for Human

Pharmaceuticals

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)

ICH

July 2001
Guidance for Industry

S7A Safety Pharmacology

Studies for Human

Pharmaceuticals

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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)

ICH

July 2001
TABLE OF CONTENTS

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

A. OBJECTIVES OF THE GUIDANCE (1.1)....................................................................................................................1

B. BACKGROUND (1.2)................................................................................................................................................1

C. SCOPE OF THE GUIDANCE (1.3)..............................................................................................................................2

D. GENERAL PRINCIPLE (1.4)......................................................................................................................................2

E. DEFINITION OF SAFETY PHARMACOLOGY (1.5)....................................................................................................2

II. GUIDANCE (2) ........................................................................................................................................................2

A. OBJECTIVES OF STUDIES (2.1)................................................................................................................................2

B. GENERAL CONSIDERATIONS IN SELECTION AND DESIGN OF SAFETY PHARMACOLOGY STUDIES (2.2).............3

C. TEST SYSTEMS (2.3) ...............................................................................................................................................3

D. DOSE LEVELS OR CONCENTRATIONS OF TEST SUBSTANCE (2.4)........................................................................5

E. DURATION OF STUDIES (2.5) .................................................................................................................................5

F. STUDIES ON METABOLITES, ISOMERS AND FINISHED PRODUCTS (2.6)................................................................5

G. SAFETY PHARMACOLOGY CORE BATTERY (2.7)..................................................................................................6

H. FOLLOW-UP AND SUPPLEMENTAL SAFETY PHARMACOLOGY STUDIES (2.8) ......................................................7

I. CONDITIONS UNDER WHICH STUDIES ARE NOT NECESSARY (2.9).....................................................................8

J. TIMING OF SAFETY PHARMACOLOGY STUDIES IN RELATION TO CLINICAL DEVELOPMENT (2.10)..................9

K. APPLICATION OF GOOD LABORATORY PRACTICE (GLP) (2.11)..........................................................................9

III. NOTES (3)............................................................................................................................................................... 10

IV. REFERENCES (4)................................................................................................................................................. 11
1

Guidance for Industry1

S7A Safety Pharmacology Studies for Human Pharmaceuticals

I. INTRODUCTION (1)2

A. Objectives of the Guidance (1.1)

This guidance was developed to help protect clinical trial participants and patients receiving

marketed products from potential adverse effects of pharmaceuticals, while avoiding

unnecessary use of animals and other resources.

This guidance provides a definition, general principles, and recommendations for safety

pharmacology studies.

B. Background (1.2)

Pharmacology studies have been performed worldwide for many years as part of the nonclinical

evaluation of pharmaceuticals for human use. There have been, however, no internationally

accepted definitions, objectives or recommendations on the design and conduct of safety

pharmacology studies. (Note 1)

The term safety pharmacology studies first appeared in ICH M3 Timing of Nonclinical Safety

Studies for the Conduct of Human Clinical Trials for Pharmaceuticals and S6 Preclinical Safety

Evaluation of Biotechnology-Derived Pharmaceuticals as studies that should be conducted to

support use of therapeutics in humans (1, 2). Details of the safety pharmacology studies,

including their definition and objectives, were left for future discussion.

 

1

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

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, November 8, 2000. 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.

2

 Arabic numbers reflect the organizational breakdown in the document endorsed by the ICH Steering Committee

at Step 4 of the ICH process, November 8, 2000.

This guidance represents the Food and Drug Administration=s current thinking on this topic. 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 statutes

and regulations.
2

C. Scope of the Guidance (1.3)

This guidance generally applies to new chemical entities and biotechnology-derived products for

human use. This guidance can be applied to marketed pharmaceuticals when appropriate (e.g.,

when adverse clinical events, a new patient population, or a new route of administration raises

concerns not previously addressed).

D. General Principle (1.4)

It is important to adopt a rational approach when selecting and conducting safety pharmacology

studies. The specific studies that should be conducted and their design will vary based on the

individual properties and intended uses of the pharmaceuticals. Scientifically valid methods

should be used, and when there are internationally recognized methods that are applicable to

pharmaceuticals, these methods are preferable. Moreover, the use of new technologies and

methodologies in accordance with sound scientific principles is encouraged.

Some safety pharmacology endpoints can be incorporated in the design of toxicology, kinetic,

and clinical studies, while in other cases these endpoints should be evaluated in specific safety

pharmacology studies. Although adverse effects of a substance may be detectable at exposures

that fall within the therapeutic range in appropriately designed safety pharmacology studies, such

effects may not be evident from observations and measurements used to detect toxicity in

conventional animal toxicity studies.

E. Definition of Safety Pharmacology (1.5)

Pharmacology studies can be divided into three categories: primary pharmacodynamic,

secondary pharmacodynamic, and safety pharmacology studies.

For the purpose of this document, safety pharmacology studies are defined as those studies that

investigate the potential undesirable pharmacodynamic effects of a substance on physiological

functions in relation to exposure in the therapeutic range and above. (See Note 2 for definitions

of primary pharmacodynamic and secondary pharmacodynamic studies.)

In some cases, information on the primary and secondary pharmacodynamic properties of the

substance contributes to the safety evaluation for potential adverse effects in humans and should

be considered along with the findings of safety pharmacology studies.

II. GUIDANCE (2)

A. Objectives of Studies (2.1)

The objectives of safety pharmacology studies are (1) to identify undesirable pharmacodynamic

properties of a substance that may have relevance to its human safety, (2) to evaluate adverse

pharmacodynamic and/or pathophysiological effects of a substance observed in toxicology

and/or clinical studies, and (3) to investigate the mechanism of the adverse pharmacodynamic

effects observed and/or suspected. The investigational plan to meet these objectives should be

clearly identified and delineated.
3

B. General Considerations in Selection and Design of Safety Pharmacology

Studies (2.2)

Since pharmacological effects vary depending on the specific properties of each test substance,

the studies should be selected and designed accordingly. The following factors should be

considered (the list is not comprehensive).

1. Effects related to the therapeutic class of the test substance, since the mechanism of action

may suggest specific adverse effects (e.g., proarrhythmia is a common feature of

antiarrhythmic agents)

2. Adverse effects associated with members of the chemical or therapeutic class, but

independent of the primary pharmacodynamic effects (e.g., antipsychotics and QT

prolongation)

3. Ligand binding or enzyme assay data suggesting a potential for adverse effects

4. Results from previous safety pharmacology studies, from secondary pharmacodynamic

studies, from toxicology studies, or from human use that warrant further investigation to

establish and characterize the relevance of these findings to potential adverse effects in

humans

During early development, sufficient information (e.g., comparative metabolism) may not always

be available to rationally select or design the studies in accordance with the points stated above;

in such circumstances, a more general approach in safety pharmacology investigations can be

applied.

A hierarchy of organ systems can be developed according to their importance with respect to

life-supporting functions. Vital organs or systems, the functions of which are acutely critical for

life (e.g., the cardiovascular, respiratory, and central nervous systems), are considered to be the

most important ones to assess in safety pharmacology studies. Other organ systems (e.g., the

renal or gastrointestinal system), the functions of which can be transiently disrupted by adverse

pharmacodynamic effects without causing irreversible harm, are of less immediate investigative

concern. Safety pharmacology evaluation of effects on these other systems may be of particular

importance when considering factors such as the likely clinical trial or patient population (e.g.,

gastrointestinal tract in Crohn’s disease, renal function in primary renal hypertension, immune

system in immunocompromised patients.).

C. Test Systems (2.3)

1. General Considerations on Test Systems (2.3.1)

Consideration should be given to the selection of relevant animal models or other test

systems so that scientifically valid information can be derived. Selection factors can

include the pharmacodynamic responsiveness of the model, pharmacokinetic profile,

species, strain, gender and age of the experimental animals, the susceptibility, sensitivity,

and reproducibility of the test system and available background data on the substance.
4

Data from humans (e.g., in vitro metabolism), when available, should also be considered

in the test system selection. The time points for the measurements should be based on

pharmacodynamic and pharmacokinetic considerations. Justification should be provided

for the selection of the particular animal model or test system. 

2. Use of In Vivo and In Vitro Studies (2.3.2)

Animal models as well as ex vivo and in vitro preparations can be used as test systems.

Ex vivo and in vitro systems can include, but are not limited to: isolated organs and

tissues, cell cultures, cellular fragments, subcellular organelles, receptors, ion channels,

transporters and enzymes. In vitro systems can be used in supportive studies (e.g., to

obtain a profile of the activity of the substance or to investigate the mechanism of effects

observed in vivo).

In conducting in vivo studies, it is preferable to use unanesthetized animals. Data from

unrestrained animals that are chronically instrumented for telemetry, data gathered using

other suitable instrumentation methods for conscious animals, or data from animals

conditioned to the laboratory environment are preferable to data from restrained or

unconditioned animals. In the use of unanesthetized animals, the avoidance of

discomfort or pain is a foremost consideration.

3. Experimental Design (2.3.3)

a. Sample Size and Use of Controls (2.3.3.1)

The size of the groups should be sufficient to allow meaningful scientific

interpretation of the data generated. Thus, the number of animals or isolated

preparations should be adequate to demonstrate or rule out the presence of a

biologically significant effect of the test substance. The sample size should take

into consideration the size of the biological effect that is of concern for humans.

Appropriate negative and positive control groups should be included in the

experimental design. In well-characterized in vivo test systems, positive controls

may not be necessary. The exclusion of controls from studies should be justified.

b. Route of Administration (2.3.3.2)

In general, the expected clinical route of administration should be used when

feasible. Regardless of the route of administration, exposure to the parent

substance and its major metabolites should be similar to or greater than that

achieved in humans when such information is available. Assessment of effects by

more than one route may be appropriate if the test substance is intended for

clinical use by more than one route of administration (e.g., oral and parenteral) or

where there are observed or anticipated significant qualitative and quantitative

differences in systemic or local exposure.
5

D. Dose Levels or Concentrations of Test Substance (2.4)

1. In Vivo Studies (2.4.1)

In vivo safety pharmacology studies should be designed to define the dose-response

relationship of the adverse effect observed. The time course (e.g., onset and duration of

response) of the adverse effect should be investigated, when feasible. Generally, the

doses eliciting the adverse effect should be compared to the doses eliciting the primary

pharmacodynamic effect in the test species or the proposed therapeutic effect in humans,

if feasible. It is recognized that there are species differences in pharmacodynamic

sensitivity. Therefore, doses should include and exceed the primary pharmacodynamic or

therapeutic range. In the absence of an adverse effect on the safety pharmacology

parameters evaluated in the study, the highest tested dose should be a dose that produces

moderate adverse effects in this or in other studies of similar route and duration. These

adverse effects can include dose-limiting pharmacodynamic effects or other toxicity. In

practice, some effects in the toxic range (e.g., tremors or fasciculation during ECG

recording) may confound the interpretation of the results and may also limit dose levels.

Testing of a single group at the limiting dose as described above may be sufficient in the

absence of an adverse effect on safety pharmacology endpoints in the test species.

2. In Vitro Studies (2.4.2)

In vitro studies should be designed to establish a concentration-effect relationship. The

range of concentrations used should be selected to increase the likelihood of detecting an

effect on the test system. The upper limit of this range may be influenced by physicochemical properties of the test substance and other assay specific factors. In the absence

of an effect, the range of concentrations selected should be justified.

E. Duration of Studies (2.5)

Safety pharmacology studies are generally performed by single-dose administration. When

pharmacodynamic effects occur only after a certain duration of treatment, or when results from

repeat dose nonclinical studies or results from use in humans give rise to concerns about safety

pharmacological effects, the duration of the safety pharmacology studies to address these effects

should be rationally based.

F. Studies on Metabolites, Isomers, and Finished Products (2.6)

Generally, any parent compound and its major metabolites that achieve, or are expected to

achieve, systemic exposure in humans should be evaluated in safety pharmacology studies.

Evaluation of major metabolites is often accomplished through studies of the parent compound

in animals. If the major human metabolites are found to be absent or present only at relatively

low concentrations in animals, assessment of the effects of such metabolites on safety

pharmacology endpoints should be considered. Additionally, if metabolites from humans are

known to substantially contribute to the pharmacological actions of the therapeutic agent, it

could be important to test such active metabolites. When the in vivo studies on the parent
6

compound have not adequately assessed metabolites, as discussed above, the tests of metabolites

can use in vitro systems based on practical considerations.

In vitro or in vivo testing of the individual isomers should also be considered when the product

contains an isomeric mixture.

Safety pharmacology studies with the finished product formulations should be conducted only

for formulations that substantially alter the pharmacokinetics and/or pharmacodynamics of the

active substance in comparison to formulations previously tested (i.e., through active excipients

such as penetration enhancers, liposomes, and other changes such as polymorphism).

G. Safety Pharmacology Core Battery (2.7)

The purpose of the safety pharmacology core battery is to investigate the effects of the test

substance on vital functions. In this regard, the cardiovascular, respiratory, and central nervous

systems are usually considered the vital organ systems that should be studied in the core battery.

In some instances, based on scientific rationale, the core battery should be supplemented (see

section H (2.8)) or need not be implemented (see also section I (2.9)).

The exclusion of certain tests or explorations of certain organs, systems or functions should be

scientifically justified.

1. Central Nervous System (2.7.1)

Effects of the test substance on the central nervous system should be assessed

appropriately. Motor activity, behavioral changes, coordination, sensory/motor reflex

responses and body temperature should be evaluated. For example, a functional

observation battery (FOB) (3), modified Irwin’s (4), or other appropriate test (5) can be

used.

2. Cardiovascular System (2.7.2)

Effects of the test substance on the cardiovascular system should be assessed

appropriately. Blood pressure, heart rate, and the electrocardiogram should be evaluated.

In vivo, in vitro and/or ex vivo evaluations, including methods for repolarization and

conductance abnormalities, should also be considered. (Note 3)

3. Respiratory System (2.7.3)

Effects of the test substance on the respiratory system should be assessed appropriately.

Respiratory rate and other measures of respiratory function (e.g., tidal volume (6) or

hemoglobin oxygen saturation) should be evaluated. Clinical observation of animals is

generally not adequate to assess respiratory function, and thus these parameters should be

quantified by using appropriate methodologies.
7

H. Follow-up and Supplemental Safety Pharmacology Studies (2.8)

Adverse effects may be suspected based on the pharmacological properties or chemical class of

the test substance. Additionally, concerns may arise from the safety pharmacology core battery,

clinical trials, pharmacovigilance, experimental in vitro or in vivo studies, or from literature

reports. When such potential adverse effects raise concern for human safety, these should be

explored in follow-up or supplemental safety pharmacology studies, as appropriate.

1. Follow-up Studies For Safety Pharmacology Core Battery (2.8.1)

Follow-up studies are meant to provide a greater depth of understanding than, or

additional knowledge to, that provided by the core battery on vital functions. The

following subsections provide lists of studies to further evaluate these organ systems for

potential adverse pharmacodynamic effects. These lists are not meant to be

comprehensive or prescriptive, and the studies should be selected on a case-by-case basis

after considering factors such as existing nonclinical or human data. In some cases, it

may be more appropriate to address these effects during the conduct of other nonclinical

and/or clinical studies.

a. Central Nervous System (2.8.1.1)

Behavioral pharmacology, learning and memory, ligand-specific binding,

neurochemistry, visual, auditory, and/or electrophysiology examinations

b. Cardiovascular System (2.8.1.2)

Cardiac output, ventricular contractility, vascular resistance, the effects of

endogenous and/or exogenous substances on the cardiovascular responses

c. Respiratory System (2.8.1.3)

Airway resistance, compliance, pulmonary arterial pressure, blood gases, blood

pH

2. Supplemental Safety Pharmacology Studies (2.8.2)

Supplemental studies are meant to evaluate potential adverse pharmacodynamic effects

on organ system functions not addressed by the core battery or repeated dose toxicity

studies when there is a cause for concern.

a. Renal/Urinary System (2.8.2.1)

Effects of the test substance on renal parameters should be assessed. For

example, urinary volume, specific gravity, osmolality, pH, fluid/electrolyte

balance, proteins, cytology, and blood chemistry determinations such as blood

urea nitrogen, creatinine, and plasma proteins can be used.
8

b. Autonomic Nervous System (2.8.2.2)

Effects of the test substance on the autonomic nervous systemshould be assessed.

For example, binding to receptors relevant for the autonomic nervous system,

functional responses to agonists or antagonists in vivo or in vitro, direct

stimulation of autonomic nerves and measurement of cardiovascular responses,

baroreflex testing, and heart rate variability can be used.

c. Gastrointestinal System (2.8.2.3)

Effects of the test substance on the gastrointestinal system should be assessed.

For example, gastric secretion, gastrointestinal injury potential, bile secretion,

transit time in vivo, ileal contraction in vitro, gastric pH measurement, and

pooling can be used.

d. Other Organ Systems (2.8.2.4)

Effects of the test substance on organ systems not investigated elsewhere should

be assessed when there is a reason for concern. For example, dependency

potential or skeletal muscle, immune, and endocrine functions can be

investigated.

I. Conditions Under Which Studies Are Not Necessary (2.9)

Safety pharmacology studies may not be needed for locally applied agents (e.g., dermal or

ocular) where the pharmacology of the test substance is well characterized, and where systemic

exposure or distribution to other organs or tissues is demonstrated to be low.

Safety pharmacology studies prior to the first administration in humans may not be needed for

cytotoxic agents for treatment of end-stage cancer patients. However, for cytotoxic agents with

novel mechanisms of action, there may be value in conducting safety pharmacology studies.

For biotechnology-derived products that achieve highly specific receptor targeting, it is often

sufficient to evaluate safety pharmacology endpoints as a part of toxicology and/or

pharmacodynamic studies; therefore, safety pharmacology studies can be reduced or eliminated

for these products.

For biotechnology-derived products that represent a novel therapeutic class and/or those products

that do not achieve highly specific receptor targeting, a more extensive evaluation by safety

pharmacology studies should be considered.

There may be additional exceptions where safety pharmacology testing is not needed, for

example, in the case of a new salt having similar pharmacokinetics and pharmacodynamics.
9

J. Timing of Safety Pharmacology Studies in Relation to Clinical Development

(2.10)

When planning a safety pharmacology program, section I (2.9) should be reviewed to determine

whether or not specific studies are recommended.

1. Studies Prior to First Administration in Humans (2.10.1)

The effects of a test substance on the functions listed in the safety pharmacology core

battery should be investigated prior to first administration in humans. Any follow-up or

supplemental studies identified as appropriate, based on a cause for concern, should also

be conducted. Information from toxicology studies adequately designed and conducted

to address safety pharmacology endpoints can result in reduction or elimination of

separate safety pharmacology studies.

2. Studies During Clinical Development (2.10.2)

Additional studies may be warranted to clarify observed or suspected adverse effects in

animals and humans during clinical development.

3. Studies Before Approval (2.10.3)

Safety pharmacology effects on systems listed in section H (2.8) should be assessed prior

to product approval, unless not warranted, in which case this should be justified.

Available information from toxicology studies adequately designed and conducted to

address safety pharmacology endpoints, or information from clinical studies, can support

this assessment and replace safety pharmacology studies.

K. Application of Good Laboratory Practice (GLP) (2.11)

It is important to ensure the quality and reliability of nonclinical safety studies. This is normally

accomplished through the conduct of the studies in compliance with GLP. Due to the unique

design of, and practical considerations for, some safety pharmacology studies, it may not be

feasible to conduct these in compliance with GLP. It has to be emphasized that data quality and

integrity in safety pharmacology studies should be ensured even in the absence of formal

adherence to the principles of GLP. When studies are not conducted in compliance with GLP,

study reconstruction should be ensured through adequate documentation of study conduct and

archiving of data. Any study or study component not conducted in compliance with GLP should

be adequately justified, and the potential impact on evaluation of the safety pharmacology

endpoints should be explained.

The safety pharmacology core battery should ordinarily be conducted in compliance with GLP.

Follow-up and supplemental studies should be conducted in compliance with GLP to the greatest

extent feasible. Safety pharmacology investigations can be part of toxicology studies; in such

cases, these studies would be conducted in compliance with GLP.

Primary pharmacodynamic studies do not need to be conducted in compliance with GLP.
10

Generally, secondary pharmacodynamic studies do not need to be conducted in compliance with

GLP. Results from secondary pharmacodynamic studies conducted during the compound

selection process may contribute to the safety pharmacology evaluation. When there is no cause

for concern (e.g., there are no findings for the safety pharmacological endpoint or the chemical

or therapeutic class), these studies need not be repeated in compliance with GLP. In some

circumstances, results of secondary pharmacodynamic studies may make a pivotal contribution

to the safety evaluation for potential adverse effects in humans, and these are normally

conducted in compliance with GLP.

III. NOTES (3)

1. General pharmacology studies have been considered an important component in drug safety

assessment. General pharmacology studies were originally referred to as those designed to

examine effects other than the primary therapeutic effect of a drug candidate. Safety

pharmacology studies were focused on identifying adverse effects on physiological functions.

All three regions have accepted data from general pharmacology studies (Japan and EC) or

safety pharmacology studies (USA) in the assessment of a marketing application. The Japanese

Ministry of Health and Welfare (MHW) issued the Guideline for General Pharmacology in

1991. In this MHW guideline, general pharmacology studies include those designed to identify

unexpected effects on organ system function and to broaden pharmacological characterization

(pharmacological profiling). However, there has been no internationally accepted definition of

the terms primary pharmacodynamics, secondary pharmacodynamics and safety

pharmacology. The need for international harmonization of the nomenclature and the

development of an international guidance for safety pharmacology has been recognized.

2. Studies on the mode of action and/or effects of a substance in relation to its desired

therapeutic target are primary pharmacodynamic studies. Studies on the mode of action and/or

effects of a substance not related to its desired therapeutic target are secondary

pharmacodynamic studies (these have sometimes been referred to as part of general

pharmacology studies).

3. There is no scientific consensus on the preferred approach to, or internationally recognized

guidance on, addressing risks for repolarization-associated ventricular tachyarrhythmia (e.g.,

Torsade de Pointes). A guidance (S7B) will be prepared to present some currently available

methods and discuss their advantages and disadvantages. Submission of data to regulatory

authorities to support the use of these methods is encouraged.
11

IV. REFERENCES (4)

1. ICH M3 Timing of Nonclinical Safety Studies for the Conduct of Human Clinical Trials for

Pharmaceuticals (FDA, 1997).

2. ICH S6 Preclinical Safety Evaluation of Biotechnology-derived Pharmaceuticals (FDA,

1997).

3. Mattsson, J. L., P. J. Spencer, and R. R. Albee, “A Performance Standard for Clinical and

Functional Observational Battery Examinations of Rats,” Journal of the American College of

Toxicology, 15: 239 (1996).

4. Irwin, S., “Comprehensive Observational Assessment: 1a. A Systematic, Quantitative

Procedure for Assessing the Behavioural and Physiologic State of the Mouse,”

Psychopharmacologia (Berlin), 13:222-257 (1968).

5. Haggerty, G. C., “Strategies for and Experience with Neurotoxicity Testing of New

Pharmaceuticals,” Journal of the American College of Toxicology, 10:677-687 (1991).

6. Murphy, D. J., “Safety Pharmacology of the Respiratory System: Techniques and Study

Design,” Drug Development Research, 32: 237-246 (1994).