PT-141 (Bremelanotide)

PT-141, the research designation for bremelanotide, is a synthetic cyclic heptapeptide (Ac-Nle-cyclo[Asp-His-D-Phe-Arg-Trp-Lys]-OH; C₅₀H₆₈N₁₄O₁₀; MW ≈ 1025.2 Da) derived by structural modification of Melanotan II (MT-II), itself a synthetic analog of alpha-melanocyte-stimulating hormone (α-MSH). Where MT-II retains strong agonism at MC1R and produces prominent skin-tanning effects, PT-141 was re-engineered for preferential activity at MC3R and MC4R while reducing MC1R tanning activity — giving it a CNS-mediated pro-sexual profile without significant melanogenesis. In June 2019 the FDA approved bremelanotide under the brand name Vyleesi (Palatin Technologies / AMAG Pharmaceuticals) for acquired, generalized hypoactive sexual desire disorder (HSDD) in premenopausal women, making it the first melanocortin receptor agonist approved for any indication in the United States. Approval was based on two identical Phase 3 randomized, double-blind, placebo-controlled trials (RECONNECT Studies 301 and 302), in which 1,247 premenopausal women received bremelanotide 1.75 mg SC as needed or placebo for 24 weeks. Both co-primary endpoints — change in FSFI desire domain score and change in FSDS-DAO item 13 (distress) — reached statistical significance. Outside its approved indication, PT-141 has been studied in early-phase trials for male erectile dysfunction, including patients with inadequate response to PDE5 inhibitors, and is used off-label by men in research and compounding contexts. These uses lack an approved indication and rely on smaller or earlier-phase evidence. Research-use material sold outside the pharmaceutical supply chain is not subject to FDA manufacturing oversight and may vary in identity, purity, and sterility. The approved Vyleesi autoinjector is the only form of bremelanotide with confirmed pharmaceutical-grade quality. This entry is for research reference only and does not constitute medical advice.