PT-141 vs Melanotan 2
PT-141, generic name bremelanotide, is a synthetic cyclic heptapeptide analogue of alpha-melanocyte-stimulating hormone that acts as a non-selective melanocortin receptor agonist and was approved by the FDA in 2019 as Vyleesi for generalised acquired hypoactive sexual desire disorder in premenopausal women. Melanotan II is a closely related non-selective melanocortin agonist that has never completed an efficacy or safety programme and is sold illegally for tanning. The two are not merely siblings: published melanocortin pharmacology describes PT-141 as the carboxylate derivative of Melanotan II, which is why the same compound family produced both a licensed sexual-medicine drug and an unlicensed tanning peptide. Two publications engage both molecules directly, but neither administered them to the same subjects, so nothing in the literature compares their effects head to head. Every claim about how they differ in potency, tolerability or risk rests on separate literatures of very unequal quality.
No study has compared them directly.
Everything below is drawn from separate studies that used different models, endpoints and species. That is a real limit on what can be concluded, not a formality.
No published study has administered bremelanotide and Melanotan II to the same subjects, in parallel arms, or in any shared experimental design, so no comparison of their effects exists. Two publications do engage both compounds directly and are listed below because they establish the relationship that most vendor material asserts without a source. King and colleagues, reviewing melanocortin receptors and penile erection, described PT-141 as the non-specific superpotent melanocortin agonist that is the carboxylate derivative of MT-II, placing the two molecules on one structural lineage; that is a review rather than an experiment. Mestria and colleagues characterised both peptides analytically by high-resolution mass spectrometry in eight unknown samples seized by police from the performance and image enhancing drug market, which identifies the molecules but says nothing about what either does in a body. Any comparison of efficacy, tolerability or long-term risk is therefore indirect, assembled from a regulated clinical programme on one side and a case-report literature of unknown denominators on the other, with no shared endpoint, population or control.
The 2 publications that cover both
- 01Review2007
Melanocortin receptors, melanotropic peptides and penile erection
King SH, Mayorov AV, Balse-Srinivasan P, Hruby VJ, Vanderah TW, Wessells H · Current Topics in Medicinal Chemistry · narrative review of central melanocortinergic control of penile erection, covering MC3R and MC4R pharmacology, receptor-selective agonists and antagonists, knockout mice and prior clinical work
The review described the non-specific superpotent melanocortin agonist PT-141 as the carboxylate derivative of MT-II and reported that it had reached phase II human trials at the time of writing. It also recorded that the MC4 receptor was emerging as the principal effector of melanocortin-induced erection while the role of MC3R remained poorly understood, and that findings from the authors' laboratories suggested forebrain MC3R antagonism might enhance melanocortin-induced erections.
- 02In vitro2021
LC-HRMS characterization of the skin pigmentation and sexual enhancers melanotan II and bremelanotide sold on the black market of performance and image enhancing drugs
Mestria S, Odoardi S, Frison G, Strano Rossi S · Drug Testing and Analysis · forensic analytical study of eight unknown samples confiscated by police alongside anabolic steroids, hormone modulators and stimulants; liquid chromatography coupled to high-resolution Orbitrap mass spectrometry with accurate mass, isotopic pattern and fragmentation analysis
Both melanotan II and bremelanotide were identified and structurally characterised in seized preparations without reference standards, the authors noting that neither compound is legally marketed in that supply chain. The work established elemental composition and structural characteristics only; it did not administer either peptide or measure any biological effect.
Side by side.
| PT-141 | Melanotan 2 | |
|---|---|---|
| Evidence maturity | Approved drug | Approved drug |
| Studies cited here | 15 | 20 |
| Published 2023 or later | 10 | 12 |
| Newest paper | 2026 | 2026 |
| Molecular relationship | Cyclic heptapeptide melanocortin agonist. Published melanocortin pharmacology describes it as the carboxylate derivative of Melanotan II, so the two share a structural lineage rather than being unrelated compounds. | Cyclic non-selective analogue of alpha-melanocyte-stimulating hormone and the parent molecule of that lineage, patented and tested clinically in the 1990s for erectile dysfunction before development moved to the derivative. |
| Receptor selectivity | Non-selective across melanocortin receptors, with activity at MC4R in central nervous system pathways considered central to its effect on sexual response. | Also non-selective, which is the stated reason its systemic effects differ from the MC1R-directed approved analogues such as afamelanotide and dersimelagon; pigmentation and sexual effects both occur. |
| Regulatory status | Approved. The FDA licensed bremelanotide in 2019 for generalised acquired hypoactive sexual desire disorder in premenopausal women, on-demand subcutaneous dosing only. | Unlicensed everywhere. No completed randomised controlled trial exists for any indication, and there is no pharmacovigilance system covering it. The approved-drug status recorded on the research entry reflects afamelanotide, a different, MC1R-selective analogue, not Melanotan II. |
| Strongest evidence tier | Two identical randomised double-blind placebo-controlled phase 3 trials (RECONNECT, 1267 participants), a 52-week open-label extension, an integrated safety analysis across 43 studies and roughly 3500 subjects, and subsequent systematic reviews and meta-analyses. | For Melanotan II itself, case reports and letters. The randomised trial evidence in this research entry belongs to afamelanotide in erythropoietic protoporphyria and vitiligo, and to dersimelagon in protoporphyria, none of which tested Melanotan II. |
| Nature of the safety record | Quantified against placebo in trials: nausea 40.0% versus 1.3%, flushing 20.3% versus 1.3%, headache 11.3% versus 1.9%, with focal hyperpigmentation in more than a third of subjects exposed to consecutive daily dosing, a regimen outside the approved on-demand use. | Uncontrolled case reports with no denominator: eruptive melanocytic naevi, melanoma and melanoma in situ, oral mucosal malignant melanoma after nasal-spray use, mucosal hyperpigmentation, depigmentation, pyoderma gangrenosum, priapism, renal infarction, rhabdomyolysis and systemic toxicity. |
| Whether melanoma risk is established | Not an issue raised in the trial programme; the pigmentation signal reported in the clinical development record is focal hyperpigmentation with frequent dosing rather than melanocytic neoplasia. | Unresolved rather than demonstrated. The reported melanoma and melanoma-in-situ cases are consistently confounded by concurrent ultraviolet and sunbed exposure, which the case records themselves state, and no controlled epidemiological study of melanotan exposure and melanoma exists. |
| What is actually in the vial | The molecule tested in the clinical programme is the molecule dispensed under a marketing authorisation, with the purity and sterility controls that implies. | Unknown by definition. Reviews of unregulated alpha-melanocyte-stimulating hormone analogues concluded that illegally supplied melanotans carry risks arising from unknown preparation, dose and sterility, and forensic mass spectrometry of seized samples was needed to establish what those preparations contained. |
And what it does not.
These two peptides sit on the same structural lineage, and published melanocortin pharmacology records that PT-141 is the carboxylate derivative of Melanotan II, so the pharmacological family resemblance is real and documented rather than assumed. What the literature does not contain is any experiment that gave both to the same subjects, which means no published basis exists for statements about relative potency, relative tolerability or relative risk. The two evidence bases are not comparable in kind: bremelanotide has randomised phase 3 data, a 52-week extension and an integrated safety analysis across roughly 3500 subjects, with independent re-analysts disputing whether the statistically significant effects are clinically meaningful, while Melanotan II has no completed trial of any design and a human record consisting of adverse-event case reports whose denominator is unknowable because supply is unregulated. The melanoma question is unresolved in both directions: the case reports are real and repeated across several countries, and they are also confounded by concurrent ultraviolet and sunbed exposure in the records themselves, so causation is neither established nor excluded. Neither compound has controlled evidence for cosmetic tanning, and bremelanotide's approval covers one sexual-medicine indication in one population by one route, not the uses that generate the comparison.
Common questions.
- Is PT-141 the same molecule as Melanotan 2?
No, but they are directly related. A 2007 review of melanocortin receptors and penile erection described PT-141 as the carboxylate derivative of MT-II, placing the two on one structural lineage within the melanocortin agonist family. They are distinct chemical entities with different regulatory histories: one completed a clinical development programme and holds a marketing authorisation, the other never entered one.
- Has any experiment given bremelanotide and melanotan II to the same subjects?
None was located. Searches of PubMed and Europe PMC returned two publications that engage both compounds: a narrative review of melanocortin pharmacology, and a forensic mass-spectrometry study that identified both peptides in samples seized from the illicit market. Neither administered either compound, so no comparative pharmacodynamic, efficacy or safety data exist.
- Do the melanoma case reports prove that melanotan II causes skin cancer?
They do not. The published cases include cutaneous melanoma, melanoma in situ, five simultaneous primary melanomas in situ and an oral mucosal malignant melanoma following nasal-spray use, and the reports themselves record concurrent tanning-bed or sunbed exposure as an acknowledged confounder. No controlled epidemiological study has examined melanotan exposure and melanoma incidence, so causality is neither demonstrated nor excluded by this literature.
- Why does most of the melanotan research entry describe afamelanotide rather than melanotan II?
Because afamelanotide is the melanocortin analogue that has randomised evidence. Its pivotal placebo-controlled trials in erythropoietic protoporphyria, a randomised vitiligo trial with narrowband UV-B, and regulator-mandated post-authorisation safety studies all concern a selective, largely MC1R-directed molecule. Melanotan II is non-selective, so its systemic effects differ, and afamelanotide trial data cannot be used to infer its safety.
- Does bremelanotide cause tanning the way melanotan II does?
The bremelanotide clinical development programme recorded focal hyperpigmentation in more than a third of subjects exposed to consecutive daily dosing, a schedule outside the approved on-demand use, rather than the generalised tanning that motivates melanotan II use. Both compounds are non-selective melanocortin agonists, so pigmentary effects are pharmacologically plausible for each, but no study has quantified them side by side.
- What is known about long-term safety for each of the two peptides?
For bremelanotide, safety data extend to a 52-week open-label extension and an integrated analysis across 43 phase 1 to 3 studies in approximately 3500 subjects, with no deaths attributed to treatment; cardiovascular outcomes with repeated dosing beyond that window remain unestablished. For melanotan II there is no safety dataset at all, because no controlled study has been completed and no pharmacovigilance system covers it.
For research purposes only. Not for human consumption, diagnosis, treatment, or prevention of any condition. Nothing on this page is medical advice, and no comparison here should be read as a recommendation of either compound.