A Multicenter Phase IIb Study of a Novel Combination of Intramuscular Androgen (Testosterone Decanoate) and Oral Progestogen (Etonogestrel) for Male Hormonal Contraception

The effect of a novel combination of oral etonogestrel (ENG) and im testosterone decanoate (TD) on suppression of gonadotropins and spermatogenesis as a potential lead for male contraception was investigated. Healthy male volunteers were randomized into two groups receiving 300 microg ENG daily and 400 mg TD every 4 (n = 55) or 6 (n = 57) wk for 48 wk. At wk 48, all men except one in the 6-wk group suppressed sperm concentration to less than 1 million/ml. Faster suppression occurred in the 4-wk group. Gonadotropins were suppressed in both groups and most consistently in the 4-wk group. During treatment, trough testosterone levels increased into the normal range in the 4-wk group but remained just below normal in the 6-wk group. All peak levels were within the normal range. After treatment cessation, recovery of sperm counts and gonadotropins to normal levels occurred in both groups. Minor effects on weight and cholesterol were noted. Fourteen subjects withdrew because of an adverse event with those possibly related to the study medication reported more frequently in the 6-wk group (nine vs. one). In conclusion, the combination of 300 microg ENG with 400 mg TD every 4 wk was superior in terms of efficacy, hormone profiles, and safety. This represents a promising approach to male hormonal contraception.