S-23

What a SARM is, in mechanistic terms

The androgen receptor is a ligand-activated nuclear transcription factor. Steroidal androgens bind it, but so do a range of non-steroidal scaffolds, and the conformation that a given ligand induces determines which coactivator and corepressor proteins are recruited. Because that coregulator complement differs between tissues, different ligands can produce different transcriptional outputs in muscle versus prostate — the mechanistic basis on which the whole SARM concept rests.

• Competitive binding assays quantifying affinity at the androgen receptor relative to reference androgens and to other compounds in the aryl propionamide series.
• Rodent studies measuring anabolic and androgenic tissue endpoints, typically levator ani muscle weight against prostate and seminal vesicle weight.
• Male contraception models, in which suppression of spermatogenesis and its reversibility after withdrawal were the primary endpoints.

Limits of the evidence

Regulatory and analytical context

Store capsules sealed in a cool, dry place and keep the solution refrigerated at 2–8 °C, tightly capped and protected from light. The compound is poorly water-soluble, so cell-based work generally uses a concentrated DMSO or ethanol stock diluted into medium, with final solvent concentration kept low and matched across every condition including vehicle controls. Verify the concentration of the supplied solution against the lot certificate before calculating dilutions. Handle as a research chemical under your laboratory's chemical hygiene plan, wear gloves and eye protection, log the lot number with each experiment and dispose of residues as chemical waste.