PT-141

PT-141 is a synthetic cyclic heptapeptide analogue of alpha-MSH, sequence Ac-Nle-cyclo[Asp-His-D-Phe-Arg-Trp-Lys]-OH. Its international non-proprietary name is bremelanotide. It is a melanocortin receptor agonist with a marked preference for MC4R. It is sold here as a 10mg lyophilised powder for in-vitro research only.

By one terminal group. Melanotan II ends in a primary amide (C₅₀H₆₉N₁₅O₉, CAS 121062-08-6). PT-141 ends in a free carboxylic acid (C₅₀H₆₈N₁₄O₁₀, CAS 189691-06-3), so it is the free-acid form of Melanotan II. The ring, the Asp5 to Lys10 lactam bridge, Nle4 and D-Phe7 are identical. The two still differ across receptor subtypes and are separate compounds.

MC4R, by a wide margin. One ¹²⁵I-NDP-alpha-MSH displacement series used BHK570 cell membranes expressing each human subtype. Bremelanotide gave Ki 0.25 nM at MC4R, 6.4 nM at MC1R, 17 nM at MC5R and 53 nM at MC3R. That is roughly 26-fold, 68-fold and 210-fold preference for MC4R. No value is reported at MC2R.

It is an open structure-activity question. The two molecules differ only at the C-terminus, so the shift must come from the change in charge and hydrogen bonding at that position. Zhang et al. (Cell Res, 2021) resolved bremelanotide bound to MC4R with Gs and described a conserved binding mode for peptide agonists. That gives a structural framework for testing the difference.

Molecular formula C₅₀H₆₈N₁₄O₁₀, molecular weight 1025.2 g/mol, CAS 189691-06-3. The sequence is Ac-Nle-cyclo[Asp-His-D-Phe-Arg-Trp-Lys]-OH, a lactam ring with an N-terminal acetyl group and a free C-terminal acid. Each vial holds 10mg of lyophilised powder, batch UKPL-5217.

Yes, they are the same compound. PT-141, PT141 and PT 141 are forms of the original development code, and bremelanotide is the non-proprietary name, CAS 189691-06-3. The hyphen has no chemical meaning. The C-terminal group does: Melanotan II differs by one amide, so check that a certificate states the free-acid sequence and a mass of 1025.2 g/mol.

No. Bremelanotide is an FDA-approved medicine in the United States, but the vial sold here is not a medicine. It holds no marketing authorisation from the MHRA and is not approved for human or veterinary use. It is supplied only as a reference material for in-vitro laboratory research.

Batch UKPL-5217 tested at 99.939% purity by RP-HPLC at Janoshik Analytical, against a ≥98.0% specification. Content quantification found 10.02mg against 10mg declared. The report, #229868, can be checked online with the lab. Oxidised tryptophan is the impurity to watch, so re-check the chromatogram after extended storage.

You can purchase PT-141 in the UK only as an analytical reference material for in-vitro laboratory research. The vial sold here is not a licensed medicine and is not approved for human or veterinary use. Buyers must be 18 or over and confirm research-only use at checkout.

UK Peptide Lab has PT-141 10mg for sale online, dispatched from the UK as a lyophilised powder. The current batch, UKPL-5217, has a published third-party certificate. Orders placed before 3pm on a working day are dispatched the same day, with free UK delivery over £69.

They are the same molecule, CAS 189691-06-3. Bremelanotide is the non-proprietary name and PT-141 the original development code. In research it serves as an MC4R-preferring reference agonist, a probe of the C-terminal group against Melanotan II, and a test analyte for cyclic-peptide analytical methods.

Batch UKPL-5217 tested at 99.939% purity by RP-HPLC. Receptor selectivity is reported as Ki values from one radioligand displacement series across MC1R, MC3R, MC4R and MC5R. Because one lab measured all four under one assay format, the ratios between subtypes are directly comparable.