Azasteroids: Structure-activity relationships for inhibition of 5α-reductase and of androgen receptor binding

Article abstract of DOI:10.1021/jm00161a028

A series of steroids, primarily 4-azasteroids, were prepared and tested in vitro as inhibitors of human and rat prostatic 5α-reductase and of binding of dihydrotestosterone to the rat androgen receptor. The primary structural modifications were changes of the A ring and of moieties attached at the C-17 position of the steroid nucleus. New A-ring modifications included 4-cyano-3-oxoΔ⁴ system in the carbocyclic series and 1α-CN, 1α-CH₃, 1α,2α-CH₂, 2β-F, 2-aza, 2-oxa, and A-homo changes in the 3-oxo-4-aza series. In addition, 4-azasteroids with a D-homo ring or methyl substitution at C-7 (α and β) or C-16 (α and β) were prepared. The majority of the C-17 substituents were prepared from reactive intermediates derived from the 17β-COOH. Enhanced 5α-reductase inhibition in both the human and rat enzyme assays is seen with 4-CN substitution on 3-oxo-Δ⁴ steroids and with a C-17 side chain incorporating a lipophilically substituted semipolar group on the 4-aza-3-oxo-5α-androstane nucleus. Fewer highly active compounds were found in the human enzyme assay than in the rat assay. Structural requirements for inhibition of the rat androgen receptor are much different from those for inhibition of the enzyme. The 17β-OH moiety enhances potency more than any other feature while introduction of double bonds at C-1 or C-5 in the azasteroid gives a small improvement. Azasteroids unsubstituted at the 4-position show greatly diminished receptor activity.