(E)-4-{2-[[3-(Indol-5-yl)-1-oxo-2-butenyl]amino]phenoxy}butyric Acid Derivatives: A New Class of Steroid 5.alpha.-Reductase Inhibitors in the Rat Prostate. 1
A series of (E)-4-2-[[3-(indol-5-yl)-1-oxo-2-butenyl]amino]phenoxy}butyric acid derivatives was prepared, and the derivatives were demonstrated to be potent inhibitors of steroid 5 alpha-reductase in the rat prostate. The structure-activity relationships were as follows. An alpha-branched alkyI or benzyl substituent of proper size at position I of the indole is crucial for optimal enzyme inhibitory activity. N-Methylation of the amide NH resulted in complete loss of activity. Thus, coplanarity of the benzene ring and amide moiety is essential for such activity. Among the compounds prepared, (E)-4-(2-[[3-[1-[bis(4-fluorophenyl)methyl]indol-5-yl]-1-oxo-2-butenyl]amino]phenoxy)butyric acid (57, KF18678) was one of the most potent compounds (rat prostate 5 alpha-reductase IC50 = 3.3 nM).
Indole Derivatives as a New Class of Steroid 5α-Reductase Inhibitors
KF20405) showed the maximum potency with an IC50 value of 0.48 +/- 0.086 nM, which was 20-fold higher potency than 1 (MK-906). Compound 16 effectively inhibited DHT production 4 h after a 3 mg/kg oral administration. Several potent indole derivatives, 1 and 2 ((+/-)-ONO-3805), were tested versus rat and human isozymes. Nonsteroidal inhibitors such as indole derivatives and 2 were 2-3 orders of magnitude