Melanotan-1 vs Melanotan-2 — How They Differ
Melanotan-1 and Melanotan-2 are both synthetic analogues of α-MSH, but they are structurally distinct compounds with different CAS numbers and properties. This page sets out the factual differences.
| Melanotan-1 (MT-1) | Melanotan-2 (MT-2) | |
|---|---|---|
| INN / other name | Afamelanotide | — |
| Structure | Linear tridecapeptide | Cyclic heptapeptide |
| CAS number | 75921-69-6 | 121062-08-6 |
| Molecular weight | ~1646.8 g/mol | ~1024.2 g/mol |
| Derived form | [Nle4, D-Phe7]-α-MSH | Cyclic α-MSH analogue |
| Related compound | — | PT-141 is its free-acid derivative |
Linear vs cyclic
Melanotan-1 (afamelanotide) is a linear 13-amino-acid analogue of alpha-melanocyte-stimulating hormone (α-MSH) with substitutions at positions 4 and 7 that increase stability and receptor affinity. Melanotan-2 is a shorter, cyclic 7-amino-acid analogue — cyclisation through a lactam bridge constrains its shape and changes its receptor-selectivity profile.
Different chemistry
Melanotan-1 (CAS 75921-69-6, ~1646.8 g/mol) is the larger molecule; Melanotan-2 (CAS 121062-08-6, ~1024.2 g/mol) is smaller and cyclic. PT-141 (bremelanotide) is closely related to Melanotan-2 — it is the free-acid derivative in which the C-terminal amide is replaced by a carboxylic acid.
Research context
Both are tool compounds in melanocortin-receptor pharmacology — receptor-binding, subtype-selectivity and signalling studies across the MC1–MC5 receptors. The literature is preclinical and pharmacological.
Regulatory status — read carefully
Neither is an approved medicine for general use. A pharmaceutical implant of afamelanotide is approved on prescription for a rare photosensitivity disorder, and UK/EU regulators (including the MHRA) have warned against consumer 'tanning' products containing Melanotan-2. Index Peptides supplies both strictly for in-vitro laboratory research — never for tanning or any human use — and support cannot discuss such uses.
Frequently asked questions
Which is stronger?
They have different structures and receptor-selectivity profiles rather than a simple strength ranking. Index Peptides supplies both as research materials only.
Is either legal to use for tanning?
No. Regulators including the MHRA have warned against consumer Melanotan tanning products. Index Peptides supplies these compounds strictly for in-vitro laboratory research, not for human use of any kind.
How does Melanotan-2 relate to PT-141?
PT-141 (bremelanotide) is the free-acid derivative of Melanotan-2, with a different CAS number, mass and pharmacological profile.
References
Research use only. Not for human or animal consumption.