BMS-564929

BMS-564929 is a synthetic, nonsteroidal selective androgen receptor modulator (SARM), a class of compounds designed to switch on the androgen receptor in a tissue-selective way rather than acting as broad steroid hormones. Chemically it is built around a bicyclic hydantoin scaffold instead of a steroid nucleus, and it carries the alternative research code PS-178990 ^[2][3]. In receptor-binding assays it is a subnanomolar agonist of the androgen receptor and is highly selective for that receptor over other steroid hormone receptors, with no meaningful interaction with sex hormone binding globulin or the aromatase enzyme ^[1].

The compound was identified and characterized by researchers at Bristol-Myers Squibb, who reported its profile in the journal Endocrinology in 2007 ^[1]. In castrated male rats, BMS-564929 stimulated growth of the levator ani muscle more potently than testosterone itself, yet, unlike testosterone, it did so with comparatively little effect on the prostate; the authors used X-ray crystallography of the ligand-bound receptor to describe the binding contacts thought to underlie this muscle-versus-prostate selectivity ^[1]. On the strength of this preclinical profile the molecule was advanced into clinical trials aimed at age-related functional decline, sometimes framed in the context of andropause, the gradual fall in androgen levels that accompanies male aging ^[1].

As with the broader SARM class, the therapeutic rationale was to reproduce the benefits of androgens on muscle and bone while avoiding the prostate stimulation and inconvenient injectable delivery that limit conventional testosterone therapy ^[1]. BMS-564929 did not proceed to marketing approval and remains an investigational compound. Because SARMs are potent anabolic agents, the World Anti-Doping Agency added the class to its Prohibited List in 2008, and BMS-564929 has since featured in analytical-chemistry work that develops mass-spectrometry and chromatography methods to detect it and related SARMs in urine and blood for doping control ^[2][3][4][5]. Reflecting its unapproved status, it is met today mainly in research and anti-doping literature, and it also circulates as an unregulated research chemical sold outside legitimate medical channels ^[4][5].

Human safety data is thin to nonexistent, so nobody really knows the long-term risks. Expect strong suppression of natural testosterone, and like other oral androgens it may stress the liver and shift cholesterol in a bad direction. This is a research chemical, not an approved drug, so purity and dosing from gray-market sources are a real gamble.