The novel drug CS-891 inhibits 5 alpha-reductase activity in freshly isolated dermal papilla of human hair follicles

The local conversion of testosterone (T) to the more potent androgen dihydr otestosterone (DHT) by 5 alpha -reductase (5aR) is implicated in the pathog enesis of androgenetic alopecia (AGA). Recently, the clinical effectiveness of finasteride, a selective type II 5aR inhibitor, in treating AGA has bee n documented, and these clinical studies have shown that circulating DHT is lowered by 60-70% in men taking finasteride. The source of the residual ci rculating DHT is presumed to be due to type T 5aR activity which is not aff ected by finasteride. Several novel compounds with potent dual inhibitory a ctivity on both isoenzymes have been described and CS-891 is one of them. T his compound may be likewise effective in the prevention or treatment of AG A. As a prerequisite for such an action CS-891 should be able to inhibit 5a R activity in its target tissue: the hair follicles (HF). Here we report on the capability of CS-891 to inhibit 5aR activity in dermal papillae (DP) o f human HF.