Spironolactone-related inhibitors of type II 17β-hydroxysteroid dehydrogenase: chemical synthesis, receptor binding affinities, and proliferative/antiproliferative activities

Abstract The family of 17β-hydroxysteroid dehydrogenases (17β-HSDs) catalyzes the formation and inactivation of testosterone (T), dihydrotestosterone (DHT), and estradiol (E 2 ), thus playing a crucial role in the regulation of active steroid hormones in target tissues. Among the five known 17β-HSD enzymes, type II catalyzes the oxidation of E 2 into estrone (E 1 ), T into androstenedione, DHT into androstanedione, and 20α-dihydroprogesterone into progesterone. Specific inhibitors are thus an interesting means to study the regulation and to probe the structure of type II 17β-HSD. In this context, we have efficiently synthesized a series of 7α-thioalkyl and 7α-thioaryl derivatives of spironolactone that inhibit type II 17β-HSD. These new C19-steroidal inhibitors possess two important pharmacophores, namely 17-spiro-γ-lactone and a bulky side-chain at the 7α-position. It was found that a para -substituted benzylthio group at the 7α-position enhances the inhibitory potency of spironolactone derivatives on type II 17β-HSD. In fact, the compound with a para -hydroxy-benzylthio group showed an IC 50 value of 0.5 μM against type II 17β-HSD, whereas the compound with a para -[2-(1-piperidinyl)-ethoxy]-benzylthio group inhibited this enzyme with an IC 50 value of 0.7 μM. The latter inhibitor is more selective than the former because it did not show any inhibitory potency against P450 aromatase as well as any affinity towards four steroid receptors (AR, PR, GR, ER). As a result, this inhibitor did not show any proliferative effect on androgen-sensitive Shionogi cells and estrogen-sensitive ZR-75-1 cells. These findings contribute to a better knowledge of the structure of type II 17β-HSD and offer an interesting tool to study the regulation of this enzyme in several biological systems.