Evaluation of STS-557 as an oral contraceptive in male rat

Twenty-one day administration of dienogest reversibly suppresses gonadotropins and testosterone in normal men

Androgen-progestin combinations are promising male contraceptive regimens. Optimization of these regimens includes the development of new progestins with more favorable biological properties. In this context we tested the effects of the progestin dienogest (DNG) on reproductive hormones and metabolic parameters in men. After a 3-wk control period, 25 men were randomly assigned to receive daily doses of 2, 5, or 10 mg DNG or placebo and 10 mg cyproterone acetate for 21 d (n = 5 subjects/group). Subjects were followed for 2 wk after cessation of hormone administration. Weekly blood samples, physical examinations, hormone and chemistry measurements, semen analysis, and sexual/behavioral assessments were performed. These parameters were compared among study groups and within each group at different time points throughout the study periods. DNG and cyproterone acetate administration resulted in profound suppression of gonadotropins and T with no change in SHBG levels. No adverse effects were detected in any subject. Hormone levels returned to baseline after stopping hormone intake. DNG is a potent suppressor of gonadotropins and T in men and does not induce adverse effects over a 21-d administration. DNG is a promising progestin to be used in clinical trials for male contraception.

Contraceptive potentiality of STS-557--a feasibility study in male bonnet monkey (Macaca radiata)

STS-557 (17 alpha-cyanomethyl-17 beta-hydroxy-estra-4, 9(10)-diene-3-one) was administered (i.m.) to two groups (4 in each group) of adult male bonnet monkeys at a daily dose of 10 mg/monkey for 12 weeks (first group) and 5 mg/monkey for 14 weeks (second group). Treatment with the 10 mg dose resulted in a significant decline in the count, motility, acrosin and hyaluronidase activities and the fertilizing ability (zona-free hamster egg penetration assay) of spermatozoa by the 6th week of initiation of treatment. The circulating level of STS-557 was low after one week and increased from the 2nd week of treatment when the serum level of testosterone was significantly reduced. Complete recovery was observed by the 11th week after withdrawal of treatment. The treatment with the 5 mg dose had minor and inconsistent effect on the motility, hyaluronidase and acrosin activity, and the fertilizing ability of spermatozoa in addition to the blood level of testosterone. STS-557 may have the potentiality to be used as a chemical contraceptive in the male but compensation for the reduced level of blood testosterone may be necessary.