Merck was maybe looking to repurpose Fin to treat Acne.
Questions have been raised as to whether finasteride, an inhibitor of type 2 5α-reductase, is beneficial in the treatment of acne. It is, however, the type 1 isozyme that clearly predominates within sebaceous glands. If sebum production is significantly regulated by locally produced dihydrotestosterone, it would be unlikely that finasteride would influence sebum production. In fact, it has been shown that there was no decrease in sebum production in men treated with 5 mg of finasteride daily.11 These data are further supported by the observation that although oral administration of 5 mg of finasteride daily for 2 weeks resulted in a substantial reduction in serum and semen dihydrotestosterone levels, only a modest reduction in sebum dihydrotestosterone levels was noted.10 Approximately 70% to 80% of serum dihydrotestosterone in men is produced by the type 2 isozyme, and 20% to 30% of circulating dihydrotestosterone is produced by the type 1 isozyme.10 Alternatively, if serum levels of dihydrotestosterone are more important than sebum dihydrotestosterone levels in regulating sebum production, dual inhibition of types 1 and 2 5α-reductase would be most effective in lowering serum dihydrotestosterone levels.