Home Research library Melanotan II vs PT-141
Comparison
Melanotan II vs PT-141
Melanotan II and PT-141 are separate research compounds. This page sets what our catalogue and the laboratory certificates state about each one side by side: identifiers, formula, molecular weight, chain length, form and storage. It describes the materials, not what they do, and carries no use guidance.
Specification, side by side
| Melanotan II | PT-141 | |
|---|---|---|
| Also known as | MT-2 | Bremelanotide |
| Catalogue shelf | Research peptides | Research peptides |
| CAS number | 121062-08-6 | 189691-06-3 |
| Molecular formula | C50H69N15O9 | C50H68N14O10 |
| Molecular weight | 1,024.2 g/mol | 1,025.2 g/mol |
| Chain length | 7 residues | 7 residues |
| Form as supplied | Lyophilized powder | Lyophilized powder |
| Storage | -20 °C, desiccated, protect from light | -20 °C, desiccated, protect from light |
| Sizes stocked | 10 mg | 10 mg |
| PubChem record | CID 92432 | CID 9941379 |
Figures are the ones printed on each product page. Purity appears only where a current laboratory certificate supports it, and links to that certificate.
What differs
- Melanotan II and PT-141 are each 7 residues long; they differ in which residues those are.
- Molecular weight: Melanotan II is 1,024.2 g/mol and PT-141 is 1,025.2 g/mol. PT-141 is the largest of the two.
- Each has its own CAS registry number (Melanotan II: 121062-08-6 and PT-141: 189691-06-3), which is how a chemical supplier tells them apart on paper.
- Their molecular formulas differ: C50H69N15O9 for Melanotan II and C50H68N14O10 for PT-141.
What each one is
Melanotan II
A cyclic lactam analogue of alpha-MSH, non-selective across MC1R, MC3R, MC4R and MC5R, though not at MC2R, which answers only to ACTH. Used to examine melanocortin receptor pharmacology, melanogenesis in melanocyte culture and central melanocortin signalling in rodent feeding studies. See Melanotan II.
PT-141
A cyclic heptapeptide melanocortin agonist and the active metabolite of melanotan II. Binds MC1R and MC3R through MC5R rather than picking one of them out; the weaker pigmentation reported against it is a matter of how long it stays around rather than of which receptors it reaches, and pigmentation is reported in the published animal work on repeated exposure. See PT-141.
Common questions
Are Melanotan II and PT-141 the same compound?
No. They are separate compounds with separate CAS registry numbers: 121062-08-6 for Melanotan II and 189691-06-3 for PT-141. They are sold as separate items and certified separately.
Which is the larger molecule, Melanotan II or PT-141?
PT-141, at 1,025.2 g/mol. Melanotan II is 1,024.2 g/mol.
Is there a certificate of analysis for Melanotan II and PT-141?
There is no current certificate on file for Melanotan II and PT-141, so no purity figure is printed for them.
Does this page say what Melanotan II and PT-141 are used for?
No. It compares the materials as chemicals: identifiers, formula, weight, chain length, form and storage. Everything here is sold for laboratory research use only, and the site publishes no use guidance.
Further reading
- Melanotan II, PT-141 and afamelanotide: one parent, three analoguesAfamelanotide, Melanotan II and bremelanotide all descend from the 13-residue hormone alpha-MSH. Two became approved drugs; Melanotan II never did. Structures, lineage, FDA's own words on MT-II, and status as of September 2026.
- Bremelanotide, Vyleesi and the intranasal program that was never approvedOne FDA-approved application, one route, and no intranasal bremelanotide product ever approved. The dates, the FDA review language that closed the nasal program, and where PT-141 sits in 2026.
Other comparisons
For laboratory research use only. Not a drug, not a supplement, not for human or veterinary use.