RAD 140, also known as Testolone, is one of several selective androgen receptor modulators (SARMs) that was initially developed as a potential alternative to testosterone replacement therapy. It should not be confused with it’s esterified form, RAD 150, also known as TLB 150.

RAD140 binds to the androgen receptors (AR) in a selective manner and does not produce the full range of androgenic effects as similar substances like testosterone, DHT, or anabolic steroids.