RU58841, also known as PSK3841 is a non-steroidal antiandrogen compound. This means that it can block the effects of androgens, or male hormones.

RU58841 has undergone trials for the treatment of androgenic alopecia (male pattern hair loss) and acne. It was found effective in treating androgenic alopecia when applied as a 5% solution to the scalp, at doses of 1-2mls per day.

RU58841 was well-tolerated in these trials when applied topically (on the skin) as it has a local effect, without circulating throughout the whole body. Unlike finasteride, RU58841 blocks both testosterone and dihydrotestosterone (DHT) from the hair follicle, while leaving DHT in the rest of the body intact.