PT-141

PT-141 is a synthetic cyclic lactam heptapeptide analogue of alpha-melanocyte-stimulating hormone, molecular formula C₅₀H₆₈N₁₄O₁₀, molecular weight 1025.2 g/mol, CAS 189691-06-3, 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, and it is supplied here as lyophilised powder for in-vitro laboratory research use only.

By one terminal group. Melanotan II terminates in a primary carboxamide (Ac-Nle-cyclo[Asp-His-D-Phe-Arg-Trp-Lys]-NH₂, C₅₀H₆₉N₁₅O₉, CAS 121062-08-6) and PT-141 terminates in a free carboxylic acid (Ac-Nle-cyclo[Asp-His-D-Phe-Arg-Trp-Lys]-OH, C₅₀H₆₈N₁₄O₁₀, CAS 189691-06-3), a difference of one nitrogen for one oxygen and about 1 Da. PT-141 is described in the analytical literature as the deamidation product of Melanotan II. The macrocycle, the Asp5 to Lys10 lactam bridge, the norleucine at position 4 and the D-phenylalanine at position 7 are identical. Despite that, the two behave very differently across receptor subtypes, and they are separate chemical entities with separate CAS numbers.

MC4R, by a wide margin. In a single radioligand displacement series against ¹²⁵I-NDP-alpha-MSH on membranes from BHK570 cells stably expressing each human subtype, bremelanotide returned Ki values of 0.25 nM at MC4R, 6.4 nM at MC1R, 17 nM at MC5R and 53 nM at MC3R (pKi 9.6, 8.2, 7.8 and 7.3). Because those numbers come from one laboratory using one assay format, the ratios are directly comparable: approximately 26-fold for MC4R over MC1R, 68-fold over MC5R and 210-fold over MC3R. No value is reported at MC2R, the adrenocorticotropin receptor, which alpha-MSH analogues of this class do not engage.

This is an active structure-activity question rather than a settled one. The two molecules are identical apart from the C-terminus, so the shift in subtype ratios has to arise from the change in charge and hydrogen-bonding capacity at that single position and from how the receptor pocket accommodates it. Cryo-EM structures of full-length MC4R in complex with heterotrimeric Gs, published in Cell Research in 2021, resolved bremelanotide alongside alpha-MSH and two other ligands in the orthosteric site and described a conserved binding mode for the peptidic agonists, which gives a structural framework for interrogating that difference. Researchers should treat the mechanism as characterised in transfected cell systems and recombinant complexes, not as evidence of any effect in humans.

Molecular formula C₅₀H₆₈N₁₄O₁₀, molecular weight 1025.2 g/mol, CAS number 189691-06-3. The sequence is Ac-Nle-cyclo[Asp-His-D-Phe-Arg-Trp-Lys]-OH, a 23-membered lactam macrocycle with an N-terminal acetyl group and a free C-terminal carboxylic acid. This vial contains 10mg of lyophilised powder, batch UKPL-5217, verified at 99.939% purity with the certificate of analysis published on this page.

They refer to the same compound. PT-141, PT141 and PT 141 are all forms of the original development code, and bremelanotide is the international non-proprietary name for the same molecule, CAS 189691-06-3. The hyphen carries no chemical meaning. What does matter when sourcing is the C-terminal group, because Melanotan II is only one deamidation step away and the two are routinely conflated in non-specialist listings. Check that the certificate of analysis states the free-acid sequence and a mass consistent with 1025.2 g/mol.

No. Bremelanotide is authorised as a medicine in the United States, but the material supplied here is not a medicine, holds no marketing authorisation from the MHRA, and is not approved for human or veterinary administration in the UK. It is supplied solely as an analytical reference material for in-vitro laboratory research. Purchasers must be aged 18 or over and must confirm research-only use at checkout. No claim is made or implied regarding any effect in humans.

The current PT-141 10mg batch, UKPL-5217, is verified at 99.939% purity by RP-HPLC at Janoshik Analytical, with 10.02mg quantified content and the certificate published on this product page. For a melanocortin analogue the impurity to watch is oxidised tryptophan, which resolves as a distinct RP-HPLC peak, so researchers repeating an assay after extended storage should re-check the chromatogram rather than assume the release figure still holds.

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.