- Men who are sexually active with WOCBP must use any contraceptive method with a failure rate of less than 1 percent per year. Men that are sexually active with WOCBP must follow instructions for birth control when the half life of the investigational drug is greater than 24 hours, contraception should be continued for a period of 90 days plus the time required for the investigational drug to undergo five half lives. The half life of nivolumab and ipilimumab is up to 25 days and 18 days, respectively. Given the blinded nature of the study, men who are sexually active with WOCBP must continue contraception for 31 weeks (90 days plus the time required for nivolumab to undergo five half lives) after the last dose of investigational drug.