Compound monograph
PT-141 (Bremelanotide)
PT-141, canonically bremelanotide, is a synthetic cyclic heptapeptide melanocortin receptor agonist, structurally the C-terminal free acid of the Melanotan II lactam scaffold.
01
Identity & nomenclature
PT-141, canonically bremelanotide, is a synthetic cyclic heptapeptide melanocortin receptor agonist, structurally the C-terminal free acid of the Melanotan II lactam scaffold.
Bremelanotide is the canonical substance name; PT-141 is the development code and the name under which the compound is most often supplied. Both denote the same molecule. The compound is structurally the C-terminal free acid of the Melanotan II scaffold — the two share a carbon count and differ by one oxygen for one nitrogen and one hydrogen.
Declared aliases and development codes: Bremelanotide, PT 141, PT-141 free base, PT-141.
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Molecular properties
| Molecular formula | C50H68N14O10 |
|---|---|
| Molecular mass | 1025.17 Da |
| CAS Registry Number | 189691-06-3 |
| PubChem CID | 9941379 |
| UNII | 6Y24O4F92S |
| Three-letter sequence | Ac–Nle–Asp–His–D-Phe–Arg–Trp–Lys–OH |
As with Melanotan II, no linear one-letter string is published here: the peptide is closed by a lactam bridge between the aspartate side-chain carboxyl and the lysine side-chain amine. The single structural difference from Melanotan II is at the C-terminus, which is a free acid rather than an amide.
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Structural characteristics
A cryo-electron microscopy structure of bremelanotide bound to the melanocortin-4 receptor in complex with heterotrimeric Gs protein has been determined, making this one of the few compounds in this library for which an exact-compound receptor-bound structure exists rather than an analog structure. The same work reports structures of the receptor bound to alpha-MSH, to afamelanotide and to a small-molecule ligand, and describes a conserved binding mode across the peptide agonists. Separate work on the activation mechanism of the same receptor used NDP-alpha-MSH and setmelanotide rather than bremelanotide; findings from that work describe the receptor, not this compound.
- Side-chain to side-chain lactam bridge, Asp to Lys
- Norleucine substitution
- D-phenylalanine substitution
Terminal features: N-terminal acetylation, C-terminal free acid.
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Molecular targets & mechanisms
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Analytical considerations
See the Melanotan II entry for the full statement of the mass problem; it applies symmetrically. The monoisotopic mass of PT-141 is 1024.52428 and that of Melanotan II is 1023.54027, and the carbon-13 isotope peak of Melanotan II sits 0.0194 Da from the PT-141 monoisotopic ion. Distinguishing them requires resolving power near 53,000. In the direction that matters commercially, a sample sold as PT-141 cannot be shown to be PT-141 rather than Melanotan II by nominal mass, by HPLC retention alone, or by a purity figure. The distinguishing measurement is either high-resolution mass spectrometry at sufficient resolving power or a separation method that resolves the amide from the acid.
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Verified bibliography
- Structural insights into ligand recognition and activation of the melanocortin-4 receptor.current
Zhang H, Chen LN, Yang D, Mao C, Shen Q, Feng W, Shen DD, Dai A, Xie S, Zhou Y, Qin J, Sun JP, Scharf DH, Hou T, Zhou T, Wang MW, Zhang Y
Cell research · 2021-08-25 · Journal Article
- Structures of active melanocortin-4 receptor-Gs-protein complexes with NDP-α-MSH and setmelanotide.current
Heyder NA, Kleinau G, Speck D, Schmidt A, Zschunke S, Szczepek M, Bauer B, Koch A, Gallandi M, Kwiatkowski D, Bürger J, Mielke T, Beck-Sickinger AG, Hildebrand PW, Spahn CMT, Hilger D, Schacherl M, Biebermann H, Hilal T, Kühnen P, Kobilka BK, Scheerer P
Cell research · 2021-09-24 · Journal Article
- Goldilocks-Inspired Design of Mid-Size Macrocycles for Selective Targeting of Human Melanocortin Receptors.current
Merlino F, Jia L, Boccino I, Carotenuto A, Tammaro F, Santoro F, Thompson PE, Grieco P
Journal of medicinal chemistry · 2026-08-13 · Journal Article
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Methodology & citation verification
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