Antiandrogenic activity of a series of des-A-steroid derivatives

In the search for new antiandrogens, a number of des-A-steroids were prepared by condensation of Grignard reagents with lactone 3. From the resulting key intermediates 5, various structural modifications were performed such as the introduction of an additional unsaturation to afford dienones 8 and aromatic derivatives 10 or the introduction of an alkyl substituent mostly in position 10 (11-13) but also in some cases in position 16 (22). In addition, 13-ethyl analogues were also prepared from lactone 4. The relative binding affinities (RBAs) for the androgen receptor of these compounds were determined under various conditions. Some compounds exhibit a capacity to interact with the receptor comparable to that of testosterone. One of the most potent compounds is 17beta-hydroxy-des-A-androsta-9,11-dien-5-one (8b), RBA value 73% of that of testosterone. More interestingly, several compounds were found to have an antiandrogenic profile in vitro and in vivo. One of the most effective compounds is 10-ethyl-17beta-hydroxy-des-A-estra-9-en-5-one (5c), which exhibits a strong local antiandrogenic activity in hamsters, without any significant systemic antiandrogenic effects. The corresponding 17beta-acetyl derivative (RU 38882) has been selected for extended pharmacological studies.