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# Guide on Drug Carcinogenicity Testing
- URL: https://www.fdaweb.com/guide-on-drug-carcinogenicity-testing/
- Published: 2021-10-05T12:00:00.000Z
- Updated: 2026-09-14T17:17:56.000Z
- Author: David McFarland
- Tags: FDA Policy/General, #legacy-id-D5150291

*Federal Register* notice: FDA has made available a draft guidance entitled *S1B(R1) Addendum to S1B Testing for Carcinogenicity of Pharmaceuticals*. The International Council for Harmonization document expands the testing scheme for assessing human carcinogenic risk of small molecule pharmaceuticals by introducing an additional approach that is not described in the original S1B Guideline. It is also intended to offer an integrative approach that provides specific weight of evidence criteria that inform whether or not a two-year rat study adds value in completing a human carcinogenicity risk assessment. Additionally, the addendum adds a plasma exposure ratio-based approach for setting the high dose in the rasH2-Tg mouse model. To view the notice, click [here](https://www.govinfo.gov/content/pkg/FR-2021-10-05/pdf/2021-21692.pdf?ref=fdaweb.com).