What is RU58841?
It is also known as RU, RU-58841, PSK-3841 or HMR-3841, and is a nonsteroidal anti-androgen (NSAA). It is also one a common SARMs (Selective Androgen Receptor Modulators). Its structure is shown below. It is nonsteroidal because it does not have the steroidal skeleton structure. It was investigated and developed by ProStrakan (a Scottish based specialty pharmaceutical company) for its potential therapeutic applications in conditions that were driven by androgens. Conditions, such as acne, hirsutism (excessive hair growth), and androgenetic alopecia (male-pattern hair loss). ProStrakan conducted two clinical studies, phase I and II, and the results of 5% RU-58841, when applied twice daily, were reported to be similar to finasteride.
How does it work?
As a non-steroidal anti-androgen, RU binds itself to androgen receptors and directly inhibits the effects of endogenous (from our own body) androgens such as testosterone and dihydrotestosterone (DHT). As a first generation non-steroidal anti-androgen, it selectively competes for the androgen receptors. This competition effectively attenuates the activity of testosterone and DHT, leading to an overall anti-androgen effect.
The way it works is similar to that of spironolactone, and ketoconazole, a key ingredient used in hair loss shampoo.
It differs from finasteride or dutasteride, which inhibits the activity of 5α-Reductase, an enzyme that converts testosterone into dihydrotestosterone (DHT). DHT is the primary hormone that causes hair loss in men. See the figure below.
Based on the mechanism, it is apparent that finasteride and dutasteride may lead to a decreased DHT level, while RU58841 does not. DHT is pivotal to a male’s sexual functionality, that is reason why some people choose RU instead of finasteride. This is also why more people are using topical finasteride instead of oral form to avoid its systemic effect (lowering DHT on the scalp instead of the whole body).
Topical RU-58841 solution has a relatively short half-life (1 hour) in comparison to Finasteride (6 hrs) and minoxidil (4 hrs).
