What is the minimum duration of continuous use that requires carcinogenicity testing for pharmaceuticals?

The requirement for carcinogenicity testing in pharmaceuticals is primarily based on the duration of exposure necessary to evaluate the potential for carcinogenesis effectively. A minimum duration of continuous use of 6 months is considered the threshold for initiating carcinogenicity studies because it is typically sufficient to allow for the identification of long-term exposure effects, including tumor development. This timeframe aligns with guidelines issued by regulatory authorities, which underscore that testing should be appropriate to capture the relevant biological effects over a period that reflects possible long-term use in humans.

Choosing 6 months as the minimum duration considers the balance between ensuring that sufficient data can be gathered while also recognizing that prolonged exposure may not always be feasible in the early clinical phases. Shorter timeframes, such as 3 months, would not generally provide a comprehensive understanding of the potential risks, while durations such as 12 or 18 months might extend beyond what is necessary for initial assessments of safety regarding carcinogenic risks in preclinical stages.