An inhibitor of steroid 5α-reductase types I and II (Kis = 6 and 7 nM, respectively); a time-dependent inhibitor with apparent Ki values of 17 and 4.3 nM at 10- and 30-minute reaction times, respectively; decreases prostate weight in a rat model of benign prostatic hypertrophy induced by testosterone at 0.045 and 0.756 mg/kg administered as a solution or in subcutaneous microspheres, respectively, daily for 28 days; also decreases prostate weight in a transgenic model of prostate cancer