Sensitivity of male reproductive endpoints in nonhuman primate toxicity studies: A statistical power analysis

To determine the sensitivity of male reproductive toxicity endpoints in NHPs we performed a power analysis of routine and triggered endpoints using control data from sexually mature Asian and Mauritian NHPs. The power to detect a 50% change from control was 13–30% for male reproductive organ weights, ∼30% for testicular volume, 6–66% for seminal analyses and 10–78% for male hormones. Overall, male reproductive endpoints have poor power (less than 80%) to detect a 50% change from control with a group size of 3 monkeys. Confidently identifying adverse male reproductive effects with these endpoints would likely require specialized study designs with larger group sizes. Triggering of non-routine endpoints in cases where there is special concern for male reproductive toxicity is unlikely to increase sensitivity to detect adverse effects.