PT-141
PT-141 (international nonproprietary name Bremelanotide) is a synthetic cyclic heptapeptide that acts as an agonist at melanocortin receptors. Its sequence is Ac-Nle-cyclo[Asp-His-D-Phe-Arg-Trp-Lys]-OH, a cyclic lactam analogue of alpha-melanocyte-stimulating hormone (α-MSH) incorporating the non-standard residues norleucine and D-phenylalanine. The compound is catalogued under CAS number 189691-06-3, with a molecular formula of C₅₀H₆₈N₁₄O₁₀ and a molecular weight of approximately 1025.18 g/mol (PubChem CID 9941379). Structurally, PT-141 is a metabolite of Melanotan II that lacks the C-terminal amide group, and it emerged from the melanocortin structure-activity research program associated with Victor Hruby’s group at the University of Arizona.
PT-141 has been characterized extensively in receptor-pharmacology, animal, and clinical research. It is supplied here strictly as a research-use chemical for in vitro and laboratory investigation, and the research-grade material is distinct from any approved pharmaceutical product. PT-141 has an approved pharmaceutical form in some jurisdictions and its regulatory status is evolving; in some territories it may be treated as a controlled or restricted substance, and local regulations should be checked before acquisition or use. It is not supplied for, and no claims are made regarding, any therapeutic use.
Important note on the evidence base: PT-141 has one of the most thoroughly documented structure-activity and receptor-binding profiles of any research peptide, in part because its development as a pharmaceutical generated an extensive public pharmacology dataset. That clinical and regulatory record pertains to the compound as an investigational or approved medicine under controlled conditions; it does not transfer to, or constitute claims about, the research-use chemical supplied here. Researchers should treat the clinical record as scientific background and consult the primary literature in the References section.
Available Products
Mechanism of Action
The research literature on PT-141 centers on its agonism at the melanocortin receptor family. The pathways below are drawn from receptor-pharmacology and preclinical work and are presented as mechanistic characterization, not as functional or therapeutic claims.
Melanocortin receptor agonism
PT-141 is a brain-penetrant agonist at melanocortin receptors, with documented binding and activation across the MC1R, MC3R, MC4R, and MC5R subtypes; the MC3R and MC4R subtypes are the focus of most central-nervous-system research interest. In cell assays, PT-141 binds the human MC4R with nanomolar affinity and induces cAMP accumulation in MC4R-expressing cells, identifying it as a functional agonist at this G-protein-coupled receptor [1]. The melanocortin system comprises five receptor subtypes with distinct tissue distributions, and PT-141’s activity profile across them is a primary reason it is used as a reference tool compound in melanocortin pharmacology.
Relationship to alpha-MSH and Melanotan II
As a cyclic lactam analogue of α-MSH, PT-141 retains the core melanocortin-active sequence while gaining metabolic stability from cyclization and the non-standard residues. Its structural relationship to Melanotan II — from which it differs by the absence of the C-terminal amide — is significant in the literature because the two compounds share the melanocortin scaffold but differ in their receptor-activity emphasis, making PT-141 a useful point of comparison in structure-activity studies of the melanocortin family [2].
Central versus peripheral activity
The melanocortin-4 receptor is expressed in the central nervous system and is implicated in the regulation of energy balance and appetite (MC4R defects are a recognized cause of monogenic early-onset obesity), as well as in other centrally mediated processes studied via MC4R agonists. PT-141’s brain penetrance and MC4R agonism make it a tool for investigating these central melanocortin pathways in research models [1]. Because the melanocortin receptor subtypes are distributed across both central and peripheral tissues — MC1R in skin and immune cells, MC2R in the adrenal cortex, MC3R and MC4R in the brain, and MC5R in exocrine tissue — a non-selective agonist such as PT-141 engages multiple pathways, and distinguishing central from peripheral contributions is a recurring methodological consideration in melanocortin research.
None of the mechanisms summarized here are presented as functional or therapeutic claims for the research-use material supplied here.
Forms and Use in the Research Literature
The information below reflects how PT-141 appears in the published literature. It is reported strictly for research-reference purposes and does not constitute administration recommendations of any kind.
Receptor and structural pharmacology. In vitro work has characterized PT-141’s binding affinity and cAMP signalling across the melanocortin receptor subtypes in receptor-expressing cell systems, and the compound features prominently in the structure-activity literature of cyclic melanocortin analogues [2].
Preclinical models. Animal work has used PT-141 to probe centrally mediated melanocortin pathways, taking advantage of its brain penetrance and MC3R/MC4R activity, with administration by parenteral and central routes in research models [1].
Clinical research record. PT-141 was administered to several thousand human subjects across dozens of completed clinical studies during its pharmaceutical development, using intranasal, intravenous, and subcutaneous formulations. As noted above, this record describes the compound under controlled medical-trial conditions and as an approved medicine, not the research-use material.
Capsule format. This product is supplied by Captide Labs in capsule form, consistent with the brand’s capsule-first catalog. Researchers should note that the published PT-141 literature predominantly used parenteral and intranasal administration, so oral or encapsulated delivery represents a distinct research variable, and oral bioavailability of this cyclic peptide is not well characterized.
Stability and storage. PT-141 is supplied as a lyophilized powder, typically stored frozen, protected from heat, light, and moisture, with reconstituted solutions kept cold and used promptly. Its cyclic lactam architecture confers greater stability than linear α-MSH analogues. Each lot supplied by Captide Labs is accompanied by a batch-specific Certificate of Analysis documenting identity and purity by HPLC.
Adverse-event profile. The pharmaceutical development of PT-141 generated a substantial clinical safety dataset, but that information describes the compound under controlled medical conditions and as an approved medicine, and does not establish a safety profile for the research-use chemical or for any use outside those settings. The evolving regulatory status of the compound is relevant context for any research use.
References
- Molinoff PB, Shadiack AM, Earle D, Diamond LE, Quon CY. PT-141: a melanocortin agonist for the treatment of sexual dysfunction. Ann N Y Acad Sci. 2003;994:96–102. doi:10.1111/j.1749-6632.2003.tb03167.x · PubMed: 12851303
- Hruby VJ, Cai M, Cain JP, Mayorov AV, Dedek MM, Trivedi D. Design and synthesis of cyclic melanotropin peptide analogues with selective agonist or antagonist activity at melanocortin receptors. Curr Med Chem. 2007;14(7):729–743. doi:10.2174/092986707780059715 · PubMed: 17346160
- Adan RA, Tiesjema B, Hillebrand JJ, la Fleur SE, Kas MJ, de Krom M. The MC4 receptor and control of appetite. Br J Pharmacol. 2006;149(7):815–827. doi:10.1038/sj.bjp.0706929 · PubMed: 17043670