Effects of a new non-steroidal 5 alpha-reductase inhibitor, FK143, on the prostate gland in beagle dogs

4-(Benzoylindolizinyl)butyric acids; novel nonsteroidal inhibitors of steroid 5alpha-reductase. III

A novel series of indolizinebutyric acids with various benzoyl substituents was synthesized to develop nonsteroidal inhibitors of steroid 5alpha-reductase, and the structure-activity relationships in this series were studied. We previously reported the structure-activity relationships in a series of indolebutyric acids as well as the discovery of the novel nonsteroidal 5alpha-reductase inhibitor, FK143. We have now made other modifications to this compound to improve in vivo inhibitory activity. By altering the heterocyclic nucleus and changing the benzoyl substituent we have succeeded in identifying the strongly active compound, FK687, (S)-4-[1-[4-[[1-(4-isobutylphenyl)butyl]oxy]benzoyl]indolizin-3-yl]butyric acid, which displays strong in vitro inhibitory activity against the human enzyme and in vivo inhibitory activity against the castrated young rat model. This compound should be a useful agent for the treatment of benign prostatic hyperplasia.

Hormonal effects of Z-350, possessing steroid 5alpha-reductase inhibitory and alpha1-adrenoceptor antagonistic actions, in the rat

We examined the hormonal effects of Z-350, (S)-4-[3-(4-[1-(4-methylphenyl)-3-[4-(2-methoxyphenyl)piperazine-1-yl]propoxy]benzoyl)indole-1-yl]butyric acid hydrochloride, which has both alpha1-adrenoceptor blocking activity and steroid 5alpha-reductase inhibitory activity, in male and female rats. Z-350 administered orally for 14 days at a dose of 30 mg/kg to normal male rats significantly reduced the weight of the prostate and seminal vesicles without affecting the weight of the testis, epididymis, adrenals, kidney or liver. Prostatic levels of dihydrotestosterone decreased dose-dependently, with a slight increase in the level of testosterone at a Z-350 dose of 100 mg/kg. We observed no effects on the weight of the prostate in castrated rats or on the weight of the uterus in normal or 17beta-estradiol-treated female rats. These results suggest that Z-350 inhibits prostatic growth via inhibition of steroid 5-reductase without other hormonal effects.