Comparison. Research use only.
Melanotan II vs PT-141 (Bremelanotide)
Melanotan II and PT-141 (Bremelanotide) are near-identical cyclic heptapeptide analogs of alpha-MSH, and both act on several melanocortin receptors. What separates them is less the molecule than the evidence and regulatory record: Bremelanotide went through a Phase 3 program and an FDA approval, while Melanotan II never progressed past small early studies.
What is the difference between Melanotan II and PT-141 (Bremelanotide)?
Melanotan II and PT-141 (Bremelanotide) are both cyclic heptapeptide analogs of alpha-MSH that act as non-selective melanocortin receptor agonists; structurally, Melanotan II ends in a C-terminal amide and Bremelanotide in a free acid. The bigger difference is evidence: Bremelanotide completed Phase 3 trials (RECONNECT) and FDA approval in 2019, while Melanotan II has only small early human studies and no approval.
| Attribute | Melanotan II | PT-141 (Bremelanotide) |
|---|---|---|
| Structure | Ac-Nle-c[Asp-His-D-Phe-Arg-Trp-Lys]-NH2 (C-terminal amide) | Ac-Nle-cyclo(Asp-His-D-Phe-Arg-Trp-Lys)-OH (C-terminal free acid) |
| Molecular weight | 1024.18 Da | 1025.2 Da (free base) |
| CAS number | 121062-08-6 | 189691-06-3 |
| Receptor profile | Non-selective agonist at MC1R through MC5R | Non-selective; labeled potency order MC1R > MC4R > MC3R > MC5R > MC2R |
| Human evidence | Phase 1 pilot (Dorr et al., 1996, n=3); two small crossover studies in men (Wessells 1998, 2000) | Phase 3 RECONNECT Studies 301 and 302 (Kingsberg et al., 2019, n=1,267) plus open-label extension (n=684) |
| Regulatory status | Not approved by any agency; warnings issued in several countries | Finished drug product FDA-approved as Vyleesi (2019) for one indication; research-grade powder is not that product |
What is Melanotan II?
Melanotan II (MT-II) is a synthetic cyclic heptapeptide (a seven-amino-acid ring) analog of alpha-melanocyte-stimulating hormone (α-MSH). It acts as a non-selective agonist at melanocortin receptors MC1R through MC5R.
Read the full Melanotan II research summary →What is PT-141 (Bremelanotide)?
Bremelanotide is a synthetic cyclic heptapeptide analog of alpha-melanocyte-stimulating hormone, and it acts as a non-selective melanocortin receptor agonist. FDA-approved labeling states that it activates several melanocortin receptor subtypes, with a rank order of potency of MC1R, MC4R, MC3R, MC5R and MC2R, and that binding at MC1R and MC4R is the most relevant at therapeutic exposures.
Read the full PT-141 (Bremelanotide) research summary →Melanotan II and PT-141 (Bremelanotide) specifications
Frequently asked questions
Are Melanotan II and PT-141 the same molecule?
No, but they are very close. Melanotan II and PT-141 (Bremelanotide) share the same cyclic seven-residue core, Ac-Nle-cyclo(Asp-His-D-Phe-Arg-Trp-Lys). Melanotan II ends in a C-terminal amide (-NH2) while Bremelanotide ends in a free acid (-OH), and their molecular weights are 1024.18 Da and 1025.2 Da respectively. They carry separate CAS numbers and have entirely separate development histories.
Do Melanotan II and PT-141 act on the same receptors?
Largely, yes. Melanotan II is described as a non-selective agonist at melanocortin receptors MC1R through MC5R. Bremelanotide's FDA labeling also describes non-selective agonism, with a potency order of MC1R, MC4R, MC3R, MC5R and MC2R, and states that the mechanism behind its clinical effect is unknown. MC1R activity is linked to pigmentation in both compounds, and MC4R to central signalling.
Have Melanotan II and PT-141 been studied in humans?
Bremelanotide (PT-141) completed two 24-week randomized Phase 3 trials, RECONNECT Studies 301 and 302 (Kingsberg et al., Obstetrics and Gynecology 2019, n=1,267), plus an open-label extension (Simon et al., 2019). Melanotan II's human record is small: a three-subject Phase 1 pilot (Dorr et al., Life Sciences 1996) and two small crossover studies in men (Wessells et al., 1998 and 2000).
Is research-grade PT-141 the same as the approved drug?
No. The FDA approved a finished Bremelanotide product, Vyleesi, in June 2019 under NDA 210557 for one indication in one population. That approval does not extend to research-grade Bremelanotide powder, which is not manufactured to pharmaceutical GMP standards. Melanotan II has no approval of any kind. Veridian supplies both PT-141 and Melanotan II strictly for in vitro and laboratory research.
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