PT-141 and Melanotan II are closely related synthetic analogs of alpha-melanocyte-stimulating hormone, but only one has an approval: PT-141 is bremelanotide, approved by the FDA in June 2019 as Vyleesi for one form of low sexual desire in premenopausal women, while Melanotan II has no approval anywhere. Melanotan II's human record is a handful of small 1990s studies plus a run of published case reports of serious adverse events in people using unregulated product.
Both act on melanocortin receptors, which is why they share some effects and why the approval of one says nothing about the other.
At a glance
| PT-141 (bremelanotide) | Melanotan II | |
|---|---|---|
| What it is | Cyclic synthetic analog of alpha-MSH | Cyclic synthetic analog of alpha-MSH |
| Origin | Developed by Palatin Technologies as an analog of Melanotan II | University of Arizona, 1990s (Hadley, Dorr and colleagues) |
| Receptors | Nonselective melanocortin agonist; MC1R and MC4R most relevant at approved exposure, per its label | Nonselective melanocortin agonist |
| Pivotal human evidence | Two phase 3 trials (RECONNECT), 1,267 premenopausal women, 24 weeks | A crossover study in 10 men with psychogenic erectile dysfunction, plus small early studies |
| Safety record | Label warnings: transient blood pressure rise, nausea, focal hyperpigmentation | Case reports of melanoma, encephalopathy, rhabdomyolysis, priapism and more |
| FDA approval | Vyleesi, June 21, 2019, for acquired, generalized HSDD in premenopausal women | None |
| US compounding review | Component of an approved drug | Listed among withdrawn Category 2 substances; expected at the next advisory meeting |
| Sport | Not named on WADA's 2026 list | Not named on WADA's 2026 list |
Shared origin
Melanocortins are a family of peptide hormones, alpha-MSH among them, that act on five receptors, MC1R to MC5R. MC1R on pigment cells drives melanin production. MC4R, found widely in the brain, is involved in appetite and, the developers proposed, sexual response.
A 2006 review by Hadley and Dorr (Peptides), from the University of Arizona group that designed the early analogs, describes two of them: a linear peptide, melanotan I, tested for skin tanning, and a cyclic, truncated peptide, Melanotan II, tested for male erectile dysfunction. The same review describes PT-141, from Palatin Technologies, as a new analog of Melanotan II then heading into later-stage trials.
A related alpha-MSH analog, afamelanotide, was approved by the FDA in October 2019 as Scenesse, an implant for adults with erythropoietic protoporphyria, a rare light-sensitivity disorder. It is a different molecule from both compounds here and is mentioned only because it is often confused with them.
The evidence for PT-141
The approval rests on the RECONNECT program. Kingsberg and colleagues (Obstetrics & Gynecology, 2019) reported two identical, randomized, double-blind, placebo-controlled phase 3 trials in premenopausal women with hypoactive sexual desire disorder (HSDD). Of 1,267 women randomized, 1,202 were in the efficacy analysis. Over 24 weeks, the bremelanotide groups showed statistically significant increases in a desire score and reductions in distress about low desire compared with placebo. The differences were modest on the scales used: an integrated increase of 0.35 points in the desire domain of the Female Sexual Function Index. Nausea, flushing and headache each affected 10% or more of participants in both trials. The trials were funded by Palatin and its licensee at the time, AMAG Pharmaceuticals.
The Vyleesi label is narrow. It covers acquired, generalized HSDD in premenopausal women, and states that the drug is not indicated for postmenopausal women or men, or to enhance sexual performance. It also says the mechanism by which it improves HSDD in women is unknown.
The label's warnings describe what the trials found: a transient rise in blood pressure and fall in heart rate after each use, which is why it is contraindicated in uncontrolled hypertension or known cardiovascular disease; nausea in 40% of patients in the trials; and focal hyperpigmentation in 1%, consistent with action at MC1R on pigment cells.
The evidence for Melanotan II
The clinical record is small and old. Wessells and colleagues (Journal of Urology, 1998) ran a double-blind, placebo-controlled crossover study in 10 men with erectile dysfunction of no known physical cause. Eight of the 10 developed erections after Melanotan II, and nausea, stretching and yawning, and decreased appetite were reported more often than with placebo. The program did not progress to approval; its successor in development was PT-141.
Since then, most of what has been published about Melanotan II in people concerns harm in unregulated use, mainly for tanning. A 2017 review in the International Journal of Dermatology (Habbema and colleagues) reported growing case reports of changes in existing moles and new atypical moles, and four case reports of melanoma arising from existing moles during or shortly after melanotan use. The authors stated that conclusive evidence linking the two is lacking and noted safety warnings from several national health authorities.
Individual case reports describe other serious events, each a single patient and none establishing cause:
- Posterior reversible encephalopathy syndrome, a form of brain swelling (Kaski and colleagues, Annals of Internal Medicine, 2013).
- Systemic toxicity with rhabdomyolysis, a breakdown of muscle tissue (Nelson and colleagues, Clinical Toxicology, 2012).
- Priapism (Devlin and colleagues, Clinical Toxicology, 2013; Dreyer and colleagues, BMJ Case Reports, 2019).
- Renal infarction (Peters and colleagues, CEN Case Reports, 2020).
The FDA's safety summary for Melanotan II summarizes the same literature, citing published case reports of melanoma, posterior reversible encephalopathy syndrome, sympathomimetic toxidrome and priapism. Case reports are the weakest form of evidence for frequency, because nobody knows how many people used the product without incident. They are also the only safety evidence that exists for it.
Regulatory status and sport
PT-141. Bremelanotide is approved as Vyleesi, and that approval belongs to the product. Material sold as "PT-141" by research suppliers is not Vyleesi. In August 2026 the FDA cited a product sold online as PT-141 among the unapproved new drugs in a warning letter to an online peptide seller. Our coverage of those letters has the detail.
Melanotan II. It has no FDA approval. It had been placed in Category 2 of the FDA's interim compounding policy and is now listed among substances whose nominations were withdrawn. Law firm Holland & Knight expects it to be among five substances at the next Pharmacy Compounding Advisory Committee meeting, before the end of February 2027. No date has been set.
Sport. Neither compound is named on the World Anti-Doping Agency's 2026 Prohibited List. Section S0 covers substances with no current approval by any government health authority for human therapeutic use, which on its wording could reach Melanotan II. Athletes should check with their own anti-doping organization.
Our guide to which peptides are FDA-approved puts bremelanotide alongside other approved peptides, and our review of the skin class covers Melanotan II's tanning use in more depth.
Frequently asked questions
Is PT-141 the same as bremelanotide?
Yes, the same molecule under its development code and its generic name. Vyleesi is the approved bremelanotide product; research-labeled PT-141 is not Vyleesi and is not approved.
What is the difference between PT-141 and Melanotan II?
They are related cyclic analogs of alpha-MSH, and PT-141 was developed from Melanotan II. PT-141 went through phase 3 trials and was approved for one indication; Melanotan II was not.
Is Melanotan II FDA-approved?
No. It has no approval in the United States or, as far as we could find, anywhere else.
What safety problems have been reported with Melanotan II?
Published case reports describe melanoma, new or changing moles, brain swelling, muscle breakdown, priapism and kidney injury in people using unregulated product. Case reports cannot establish cause or frequency.
Sources:
- Hadley and Dorr, Peptides, 2006 (melanocortin analog history, Melanotan II and PT-141)
- Dhillon and Keam, Drugs, 2019 (bremelanotide: first approval)
- Kingsberg et al., Obstet Gynecol, 2019 (RECONNECT phase 3 trials)
- FDA approval letter, Vyleesi (bremelanotide), NDA 210557, June 21, 2019
- Vyleesi prescribing information, 2019
- Wessells et al., J Urol, 1998 (Melanotan II, 10 men, crossover)
- Habbema et al., Int J Dermatol, 2017 (review of unregulated alpha-MSH analog use)
- Kaski et al., Ann Intern Med, 2013 (posterior reversible encephalopathy syndrome)
- Nelson et al., Clin Toxicol, 2012 (systemic toxicity and rhabdomyolysis)
- Devlin et al., Clin Toxicol, 2013 (priapism)
- Dreyer et al., BMJ Case Rep, 2019 (priapism)
- Peters et al., CEN Case Rep, 2020 (renal infarction)
- Clinuvel, FDA approves Scenesse, October 8, 2019
- FDA, Certain bulk drug substances for use in compounding that may present significant safety risks
- FDA warning letter to Peak Performance Peptides, August 24, 2026
- Holland & Knight, Peptides at a crossroads, October 16, 2026
- WADA 2026 Prohibited List, as published in the Dutch treaty series
Apart from Vyleesi, the approved bremelanotide product, no compound discussed here is FDA-approved. Nothing above is dosing guidance or a treatment claim. Research use only.
For research use only · Not for human or veterinary use · No research compound discussed here is FDA-approved for any indication