Selective androgen receptor modulator
Selective Androgen Receptor Modulators or SARMs are a class of androgen receptor ligands that were developed with the intention of maintaining some of the desirable effects of androgens, such as preventing osteoporosis and muscle loss while reducing risks of undesirable conditions such as prostate cancer. In the late 1990s, the first nonsteroidal SARM, an analog of bicalutamide, was discovered at Imperial Chemical Industries. Although bicalutamide itself is an antiandrogen, its discovery encouraged a search for non-steroidal agonists of androgen receptors, as it was well-known, that small structural changes can transform a receptor antagonist into an agonist (see "Lock and key" model). It was expected, that non-steroidal androgens could provide similar positive effects as anabolic-androgenic steroids, but with fewer side effects. Although some work on SARMs was done as early as 1940s, it was not until the late 1990s, when researchers at Ligand Pharmaceuticals and the University of Tennessee discovered a new class of cyclic, nonsteroidal quinolinones, with a high anabolic activity in skeletal muscles, and variable selectivy in other tissues. At present, there are no SARMs which have been approved for therapeutic use by the U.S. Food and Drug Administration. The binding of ligands to the androgen receptor (AR) results in a conformational change, this consequentially alters surface topology which will lead to tissue-specific gene regulation. This tissue-specific regulation then allows for the selective stimulation or inhibition of the AR; this requires androgen response elements, co-regulators, and transcription factors. Although the exact mechanisms still remain unclear, tissue specificity and complexity of the pathway is known to dictate the transcriptional and cellular response. There have been experiments using a SARMs C-6 and S-23 on male mice as a contraceptive agent. Treatment of osteoporosis has been explored as SARMs have been found to have trophic effects on bone density and mineralization.
