In an October 5 Federal Register notice (86 FR 54982;, the U.S. Food and Drug Administration (FDA) announced draft guidance for industry, “S1B(R1) Addendum to S1B Testing for Carcinogenicity of Pharmaceuticals.” The draft guidance expands the testing scheme for assessing human carcinogenic risk of small molecule pharmaceuticals. It introduces an integrative approach that provides specific weight-of-evidence criteria that inform whether a 2-year rat study adds value in completing a human carcinogenicity risk assessment. The draft guidance also adds a plasma exposure ratio-based approach for setting the high dose in the rasH2-Tg mouse model.

FDA is accepting comments on the draft guidance through December 6. The draft guidance and a link to submit comments are available at