S1A: Need for Carcinogenicity Studies of Pharmaceuticals

December 23, 2002

Our file number: 02-122028-691

Notice - Withdrawal of Toxicological Evaluation Guidelines and Re-issuance of ICH Safety Guidances

The Health Canada Toxicological Evaluation guidances (revised 1996) are being withdrawn following an internal review by a Safety Expert Working Group which concluded that they no longer reflected current toxicological methodologies. Furthermore, the review revealed substantial areas of overlap and inconsistency between these guidances and their more recently adopted ICH counterparts.

The following Health Canada-adopted ICH Safety (Nonclinical) guidances, previously available as part of the Toxicological Evaluation guidances, are being re-issued as stand alone documents:

  1. S1A Need for Carcinogenicity Studies of Pharmaceuticals
  2. S2A Guidance on Specific Aspects of Regulatory Genotoxicity Tests For Pharmaceuticals
  3. S3A Note for Guidance on Toxicokinetics: The Assessment of Systemic Exposure in Toxicity Studies
  4. S3B Pharmacokinetics: Guidance for Repeated Dose Tissue Distribution Studies
  5. S5A Detection of Toxicity to Reproduction for Medicinal Products

These ICH guidances have been developed by the appropriate ICH Expert Working Group and have been subject to consultation by the regulatory parties, in accordance with the ICH Process. The ICH Steering Committee has endorsed the final draft and recommended its adoption by the regulatory bodies of the European Union, Japan and USA.

In adopting these ICH guidances, Health Canada as observer to ICH, endorses the principles and practices described therein. These documents should be read in conjunction with this covering notice and with the relevant sections of other applicable Health Canada guidance.

These and other guidance documents are currently available on the Therapeutic Products Directorate / Biologics and Genetic Therapies Directorate Website (s) (http://www.hc-sc.gc.ca/hpfb-dgpsa/tpd-dpt/). The availability of printed copies of guidance documents may be confirmed by consulting the Guidelines and Publications Order Forms (available on the TPD/BGTD Website) or by contacting the Publications Coordinator 2.

Should you have any questions regarding the content of the guidance, please contact

Colette F. Strnad, B. Sc., Ph.D.
Title: Senior Scientific Advisor Office of Science Therapeutic Products
Directorate Holland Cross,
Tower B, 2nd Floor,
A.L. 3102C3 1600 Scott Street
Ottawa, Ontario K1A 1B6
telephone: (613) 941-3693
fax: (613) 941-5035
email: colette_strnad@hc-sc.gc.ca

Guidance for Industry

Published by authority of the Minister of Health


Health Products and Food Branch Guidance Document

© Minister of Public Works and Government Services Canada 1996

Available in Canada through
Health Canada -
Publications Brooke Claxton Building,
A.L. #0913A Tunney's Pasture
Ottawa, Ontario K1A 0K9
Tel: (613) 954-5995
Fax: (613) 941-5366


This guidance has been developed by the appropriate ICH Expert Working Group and has been subject to consultation by the regulatory parties, in accordance with the ICH Process. The ICH Steering Committee has endorsed the final draft and recommended its adoption by the regulatory bodies of the European Union, Japan and USA.

In adopting this ICH guidance, Health Canada endorses the principles and practices described therein. This document should be read in conjunction with the accompanying notice and the relevant sections of other applicable guidances.

Guidance documents are meant to provide assistance to industry and health care professionals on how to comply with the policies and governing statutes and regulations. They also serve to provide review and compliance guidance to staff, thereby ensuring that mandates are implemented in a fair, consistent and effective manner.

Guidance documents are administrative instruments not having force of law and, as such, allow for flexibility in approach. Alternate approaches to the principles and practices described in this document may be acceptable provided they are supported by adequate scientific justification. Alternate approaches should be discussed in advance with the relevant program area to avoid the possible finding that applicable statutory or regulatory requirements have not been met.

As a corollary to the above, it is equally important to note that Health Canada reserves the right to request information or material, or define conditions not specifically described in this guidance, in order to allow the Department to adequately assess the safety, efficacy or quality of a therapeutic product. Health Canada is committed to ensuring that such requests are justifiable and that decisions are clearly documented.

Table of Contents

  1. Introduction
  2. Historical Background
  3. Objective of this Guidance Document
  4. Factors to Consider for Carcinogenicity Testing
    • 4.1 Duration and Exposure
    • 4.2 Cause for Concern
    • 4.3 Genotoxicity
    • 4.4 Indication and Patient Population
    • 4.5 Route of Exposure
    • 4.6 Extent of Systemic Exposure
    • 4.7 Endogenous Peptides and Protein Substances or their Analogs
  5. Need for Additional Testing

1. Introduction

The objectives of carcinogenicity studies are to identify a tumorigenic potential in animals and to assess the relevant risk in humans. Any cause for concern derived from laboratory investigations, animal toxicology studies, and data in humans may lead to a need for carcinogenicity studies. The practice of requiring carcinogenicity studies in rodents was instituted for pharmaceuticals that were expected to be administered regularly over a substantial part of a patient's lifetime. The design and interpretation of the results from these studies preceded much of the available current technology to test for genotoxic potential and the more recent advances in technologies to assess systemic exposure. These studies also preceded our current understanding of tumorigenesis with non-genotoxic agents. Results from genotoxicity studies, toxicokinetics, and mechanistic studies can now be routinely applied in preclinical safety assessment. These additional data are important not only in considering whether to perform carcinogenicity studies but for interpreting study outcomes with respect to relevance for human safety. Since carcinogenicity studies are time consuming and resource intensive they should only be performed when human exposure warrants the need for information from life-time studies in animals in order to assess carcinogenic potential.

2. Historical Background

In Japan, according to the 1990 "Guidelines for Toxicity Studies of Drugs Manual," carcinogenicity studies were needed if the clinical use was expected to be continuously for 6 months or longer. If there was cause for concern, pharmaceuticals generally used continuously for less than 6 months may have needed carcinogenicity studies. In the United States, most pharmaceuticals were tested in animals for their carcinogenic potential before widespread use in humans. According to the U.S. Food and Drug Administration, pharmaceuticals generally used for 3 months or more required carcinogenicity studies. In Europe, the Rules Governing Medicinal Products in the European Community defined the circumstances when carcinogenicity studies were required. These circumstances included administration over a substantial period of fife, ie., continuously during a minimum period of 6 months or frequently in an intermittent manner so that the total exposure was similar.

3. Objective of this Guidance Document

The objective of this guidance document is to define the conditions under which carcinogenicity studies should be conducted to avoid the unnecessary use of animals in testing, and to provide consistency in worldwide regulatory assessments of applications. It is expected that theft studies will be performed in a manner that reflects currently accepted scientific standards.

The fundamental considerations in assessing the need for carcinogenicity studies are the maximum duration of patient treatment and any perceived cause for concern arising from other investigations. Other factors may also be considered such as the intended patient population, prior assessment of carcinogenic potential the extent of systemic exposure, the (dis)similarity to endogenous substances, the appropriate study design, or the timing of study performance relative to clinical development.

4. Factors to Consider for Carcinogenicity Testing

4.1 Duration and Exposure

Carcinogenicity studies should be performed for any pharmaceutical whose expected clinical use is continuous for at least 6 months (see Note 1).

Certain classes of compounds may not be used continuously over a minimum of 6 months but may be expected to be used repeatedly in an intermittent manner. It is difficult to determine and to justify scientifically what time represents a clinically relevant treatment periods for frequent use with regard to carcinogenic potential, especially for discontinuous treatment periods. For pharmaceuticals used frequently in an intermittent manner in the treatment of chronic or recurrent conditions, carcinogenicity studies are generally needed. Examples of such conditions include allergic rhinitis, depression and anxiety. Carcinogenicity studies may also need to be considered for certain delivery systems which may result in prolonged exposures. Pharmaceuticals administered infrequently or for short duration of exposure (e.g., anesthetics and radiolabeled imaging agents) do not need carcinogenicity studies unless there is cause for concern.

4.2 Cause for Concern

Carcinogenicity studies may be recommended for some pharmaceuticals if there is concern about their carcinogenic potential. Criteria for defining these cases should be very carefully considered because this is the most important reason to conduct carcinogenicity studies for most categories of pharmaceuticals. Several factors which could be considered may include: (1) previous demonstration of carcinogenic potential in the product class that is considered relevant to humans, (2) structure-activity relationship suggesting carcinogenic risk; (3) evidence of preneoplastic lesions in repeated dose toxicity studies; and (4) long-term tissue retention of parent compound or metabolite(s) resulting in local tissue reactions or other pathophysiological responses.

4.3 Genotoxicity

Unequivocally genotoxic compounds, in the absence of other data, are presumed to be transspecies carcinogens, implying a hazard to humans. Such compounds need not be subjected to long-term carcinogenicity studies. However, if such a drug is intended to be administered chronically to humans a chronic toxicity study (up to one year) may be necessary to detect early tumorigenic effects.

Assessment of the genotoxic potential of a compound should take into account the totality of the findings and acknowledge the intrinsic value and limitations of both in vitro and in vivo tests. The test battery approach of in vitro and in vivo tests is designed to reduce the risk of false negative results for compounds with genotoxic potential. A single positive result in any assay for genotoxicity does not necessarily mean that the test compound poses a genotoxic hazard to humans (ICH Guidance on Specific Aspects of Regulatory Genotoxicity Tests).

4.4 Indication and Patient Population

When carcinogenicity studies are required they usually need to be completed before application for marketing approval. However, completed rodent carcinogenicity studies are not needed in advance of the conduct of large scale clinical trials, unless there is special concern for the patient population.

For pharmaceuticals developed to treat certain serious diseases, carcinogenicity testing need not be conducted before market approval although these studies should be conducted postapproval. This speeds the availability of pharmaceuticals for life-threatening or severely debilitating diseases, especially where no satisfactory alternative therapy exists.

In instances where the life-expectancy in the indicated population is short (i.e. less than 2-3 years) no long-term carcinogenicity studies may be required. For example, oncolytic agents intended for treatment of advanced systemic disease do not generally need carcinogenicity studies. In cases where the therapeutic agent for cancer is generally successful and life is significantly prolonged there may be later concerns regarding secondary cancers. When such pharmaceuticals are intended for adjuvant therapy in tumor free patients or for prolonged use in noncancer indications, carcinogenicity studies are usually needed.

4.5 Route of Exposure

The route of exposure in animals should be the same as the intended clinical route when feasible (ICH Dose Selection for Carcinogenicity Studies of Pharmaceuticals). If similar metabolism and systemic exposure can be demonstrated by differing routes of administration, then carcinogenicity studies should only be conducted by a single route, recognizing that it is important that relevant organs for the clinical route (e.g. lung for inhalational agents) be adequately exposed to the test material. Evidence of adequate exposure may be derived from pharmacokinetic data (ICH Guidance on Repeated Dose Tissue Distribution Studies).

4.6 Extent of Systemic Exposure

Pharmaceuticals applied topically (e.g., dermal and ocular routes of administration) may need carcinogenicity studies. Pharmaceuticals showing poor systemic exposure from topical routes in humans may not need studies by the oral route to assess the carcinogenic potential to internal organs. Where there is cause for concern for photocarcinogenic potential carcinogenicity studies by dermal application (generally in mice) may be needed. Pharmaceuticals administered by the ocular route may not require carcinogenicity studies unless there is cause for concern or unless there is significant systemic exposure.

For different salts, acids, or bases of the same therapeutic moiety, where prior carcinogenicity studies are available, evidence should be provided that there are no significant changes in pharmacokinetics, pharmacodynamics, or toxicity. When changes in exposure and consequent toxicity are noted, then additional bridging studies may be used to determine whether additional carcinogenicity studies are needed. For esters and complex derivatives, similar data would be valuable in assessing the need for an additional carcinogenicity study, but this should be considered on a case-by-case basis.

4.7 Endogenous Peptides and Protein Substances or their Analogs

Endogenous peptides or proteins and their analogs, produced by chemical synthesis, by extraction/purification from an animal/human source or by biotechnological methods such as recombinant DNA technology may require special considerations.

Carcinogenicity studies are not generally needed for endogenous substances given essentially as replacement therapy (i.e., physiological levels), particularly where there is previous clinical experience with similar products (for example, animal insulins, pituitary-derived growth hormone, and calcitonin).

Although not usually necessary, long-term carcinogenicity studies in rodent species should be considered for the other biotechnology products noted above, if indicated by the treatment duration, clinical indication or patient population (providing neutralizing antibodies are not elicited to such an extent in repeated dose studies as to invalidate the results). Conduct of carcinogenicity studies may be important in the following circumstances: (1) for products where there are significant differences in biological effects to the natural counterparts); (2) for products where modifications lead to significant changes in structure compared to the natural counterpart; and (3) for products resulting in humans in a significant increase over the existing local or systemic concentration (i.e., pharmacological levels)

5. Need for Additional Testing

The relevance of the results obtained from animal carcinogenicity studies for assessment of human safety are often cause for debate. Further research may be needed, investigating the mode of action, which may result in confirming the presence or the lack of carcinogenic potential for humans. Mechanistic studies are useful to evaluate the relevance of tumor findings in animals for human safely.

1 ICH - International Conference on Harmonization of Technical Requirements for the Registration of Pharmaceuticals for Human Use

2 Tel: (613) 954-6466; E-mail: publications_coordinator@hc-sc.gc.ca

Supplementary Note

Note 1: It is expected that most pharmaceuticals indicated for 3-months treatment would also likely be used for 6 months. In an inquiry to a number of pharmaceutical research and regulatory groups no cases were identified in which a pharmaceutical would be used only for 3 months.

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