MK – 2866 (CAS 841205 – 47 – 8) is a high – purity SARM API with a stable molecular formula of C19H14F3N3O3 and a molecular weight of 389.33. It binds selectively to androgen receptors, exerting targeted anabolic effects on skeletal muscle without causing adverse effects on the prostate or secondary sexual characteristics like traditional androgens. Even at low doses of 3mg, it can effectively promote protein synthesis and inhibit muscle loss.