Carcinogenicity testing in drug development: Getting it right

For a pharmaceutical drug, carcinogenicity testing occurs in rodents to identify its tumorigenic potential to allow assessment of the risk from its use in humans. Testing takes the form of 2-year studies in mice and rats and/or more recently, a 6-month study in transgenic mice. This paper examines the process of regulatory interaction regarding carcinogenicity testing, notably through the United States (US) Food and Drug Administration (FDA) Special Protocol Assessment (SPA) process to seek Executive Carcinogenicity Assessment Committee (ECAC) approval. The content of 37 submissions to CAC were examined. The paper also examines the outcome from such agency engagement, notably around study dose level selection as well as looking at the design of proposed carcinogenicity study protocols used in submissions (including numbers of animals, control group aspects and toxicokinetic [TK] evaluation). Overall, it was shown that the current process of regulatory interaction allows for studies acceptable to support eventual drug approval and marketing. However, it was established that areas exist to improve the content of submission documents and study design aspects.