Research Guide · 6 min read · Updated 2026-08-01
Melanotan II vs PT-141: Melanocortin Research Compared
Melanotan II and PT-141 (Bremelanotide) share the same cyclic heptapeptide core and differ by a single functional group — yet that difference reshapes their research profiles. This comparison explains the structural relationship, receptor coverage in the literature, and when laboratories choose one over the other.
One Functional Group Apart
Melanotan II is Ac-Nle-cyclo[Asp-His-D-Phe-Arg-Trp-Lys]-NH2 — a C-terminal amide. PT-141 is the same cyclic core with a free C-terminal carboxylic acid. That single change shifts receptor behaviour documented in the literature, with PT-141 showing a more CNS-focused profile via the MC4R subtype.
Receptor Coverage in the Literature
Melanotan II is used as a broad reference agonist with documented activity across melanocortin subtypes MC1R through MC5R — which is why pigmentation-pathway research (MC1R) and energy-homeostasis research (MC3R/MC4R) both cite it. PT-141's literature concentrates on MC4R-mediated central pathways, and it carries one of the deepest clinical documentation sets of any melanocortin peptide.
Handling Differences
Both are lyophilised and stored at -20°C; Melanotan II should additionally be protected from light. After reconstitution, refrigerate both at 2–8°C; PT-141 should be used within 21 days. Verify molecular weights on your COA: MT-2 at 1024.2 g/mol, PT-141 at 1025.2 g/mol — a one-dalton difference your mass spectrometry must resolve correctly.
