Novel 17 substituted pregnadiene derivatives as 5 alpha-reductase inhibitors and their binding affinity for the androgen receptor.

The in vitro antiandrogenic activity of four new progesterone derivatives: 4, 5, 6 and 7 (8 is a known compound) was determined. These compounds were evaluated as 5alpha-reductase inhibitors as well as by their capacity to bind to the androgen receptor in gonadectomized hamster prostate. The IC(50) value was determined using increasing concentrations of 4, 5, 6, 7 and 8 in the presence of [(3)H]T and the microsomal fraction of the hamster prostate containing the 5alpha-reductase enzyme. In this paper we also demonstrated the effect of increasing concentrations of the novel steroids upon [(3)H]DHT binding to the androgen receptors from hamster prostate which produces competition for the androgen receptor sites. The in vitro studies showed that steroids 4, 5, 6, 7 and 8 had an inhibitory activity for the 5alpha-reductase with IC(50) of: 4 (0.17 microM), 5 (0.19 microM), 6 (1 microM), 7 (4.2 microM), and 8 (2.7 microM). On the other hand, the IC(50) value for compounds 4, 5, 6, 7, 8 and DHT showed the following order of affinity for the androgen receptor: 6>7>5>DHT. Surprisingly compounds 4 and 8 did not bind to the androgen receptor. The overall data indicate that all synthesized compounds are inhibitors for the enzyme 5alpha-reductase present in the hamster prostate. In contrast, compounds 5, 6 and 7, which have a cyclohexyl group in the side chain showed a high affinity for the androgen receptor.