Win 32,729, a new, potent interceptive agent in rats and rhesus monkeys.

Win 32,729 [(2 alpha, 4 alpha, 5 alpha, 17 beta)-4,5-epoxy-17-hydroxy-4,17-dimethyl-3-oxoandrostane-2-carbonitrile] is an orally active interceptive agent in rats and rhesus monkeys (M mulatta). A single oral dose of 48 mg/kg terminated gestation when given on Day 10 of pregnancy. When given orally for up to 5 days to pregnant monkeys, it terminated pregnancy in 26 of 34 animals at a dose of 50 mg/monkey (ca 7 mg/kg), in 18 of 24 at a dose of 100 mg/monkey (ca 14 mg/kg) and in all 6 at 250 mg/monkey (ca 35 mg/kg). It did not inhibit ACTH-stimulated glucocorticoid production at 50 mg/monkey but did at a dose of 250 mg/monkey. This preferential gonadal inhibition was not evident in rodents. While in most cases five oral medications of 50-100 mg were required to terminate gestation in 50-day pregnant monkeys, a single subcutaneous medication with 250 mg was also effective, terminating pregnancy in 7 of 7 monkeys.