Topterone (Win 17,665) is a potent topical antiandrogen that inhibits the stimulation of lumbar organ development by testosterone and dihydrotestosterone in castrated immature male hamsters.

To determine its endocrine profile, Topterone is administered parenterally or topically to rats, rabbits, or hamsters. Systemic administration reveals that Topterone exhibits both antiandrogenic and progestational effects. However, topical application at a dose of 1 g/kg/day fails to induce a systemic antiandrogenic response, and only a minimal progestational response is observed at 32 mg/kg/day. No other endocrine activities are detected in these experiments[2].
Topterone demonstrates the inhibition of flank organ development in castrated immature male hamsters in response to both testosterone and dihydrotestosterone, whereas Progesterone inhibits stimulation by only testosterone. Furthermore, topical application of Topterone has been shown to cause regression in the development of the flank organ[1].