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The one melanocortin peptide with a drug approval — and a 40% nausea rate, a 2024 critique of its effect sizes, and a grey market that borrowed its code name.
Also known as: PT-141 · PT141 · Vyleesi · bremelanotide acetate
Part of the Neuropeptides & signaling cluster
Overview
Bremelanotide, developed as PT-141, is a cyclic seven-residue analogue of α-melanocyte-stimulating hormone that activates melanocortin receptors, with its effect on sexual desire attributed to MC3 and MC4 signalling in the brain. The FDA approved it in 2019 as Vyleesi, an on-demand subcutaneous autoinjector for premenopausal women with acquired, generalised hypoactive sexual desire disorder. Nausea occurred in 40% of phase 3 participants, and a 2024 reanalysis found effect sizes from nil to small on most trial outcomes.
Source & context
Biological / chemical source: Synthetic peptide (melanocortin analog)
Primary research or clinical context: Approved in the US (June 2019, Vyleesi) for premenopausal women with acquired, generalised hypoactive sexual desire disorder; on-demand subcutaneous autoinjector. Grey-market “PT-141” is not the approved product
What bremelanotide is
Bremelanotide is a synthetic cyclic peptide analogue of α-melanocyte-stimulating hormone (α-MSH), the 13-residue hormone that drives skin pigmentation and, through brain receptors, influences appetite and sexual behaviour. Its development code at Palatin Technologies was PT-141, which is the name the grey market still uses. The IUPHAR record describes it as a stabilised, cyclic derivative of α-MSH with little selectivity across the melanocortin receptor family apart from MC2, the ACTH receptor, and attributes its effect on sexual desire to agonism at MC3 and MC4 receptors. Formula C50H68N14O10, average mass about 1,025 Da.
Structure and how it relates to Melanotan II
Bremelanotide is a heptapeptide cyclised through a lactam bridge between an aspartate and a lysine side chain, with norleucine at position 1 and a D-phenylalanine at position 4 — the same design choices that make Melanotan II potent and resistant to breakdown. The difference is at the C-terminus: bremelanotide is the free-acid (des-amide) form, Melanotan II the amide. That single change separates an approved medicine with a defined indication from an unlicensed tanning peptide sold online, and the two are frequently confused in vendor listings. The Melanotan II profile and the melanotan comparison guide cover the sibling.
Mechanism
Melanocortin receptors are G-protein-coupled receptors; MC1 governs melanin production in skin, MC4 is a central regulator of energy balance and sexual function, and MC3 overlaps with it. Bremelanotide's clinical effect is thought to arise from MC3 and MC4 agonism in brain pathways involved in sexual response (Dhillon and Keam, Drugs 2019), which distinguishes it from every earlier drug for female sexual desire, which acted on serotonin or dopamine. Its non-selectivity also explains its side effects: MC1 activation causes flushing and, with repeated dosing, focal hyperpigmentation.
Approval and the trial programme
The FDA approved bremelanotide as Vyleesi in June 2019 for premenopausal women with acquired, generalised hypoactive sexual desire disorder (HSDD) — low desire causing marked distress or interpersonal difficulty — as a self-administered, on-demand subcutaneous injection; Palatin ran the phase 3 RECONNECT trials and licensed North American rights to AMAG (Dhillon and Keam, Drugs 2019). The safety review across the development programme covered 3,500 subjects in 43 completed studies, with phase 3 participants treated for up to 18 months (Clayton et al., Journal of Women's Health 2022). Ten trials are registered on ClinicalTrials.gov, including a completed phase 3 bridging study and a phase 2 co-administration study.
Side effects reported in phase 3
In the integrated double-blind phase 3 population of 1,247 women, the most common adverse events with bremelanotide versus placebo were nausea (40.0% vs 1.3%), flushing (20.3% vs 1.3%), headache (11.3% vs 1.9%) and injection-site reactions (5.4% vs 0.5%) (Clayton et al. 2022). Nausea was the most common reason for discontinuation. The LiverTox database notes mild serum enzyme elevations during therapy and rare reports of clinically apparent acute liver injury. The label also warns of transient blood-pressure increases after each dose, which is why the approved use limits dosing frequency.
| Event | Bremelanotide | Placebo |
|---|---|---|
| Nausea | 40.0% | 1.3% |
| Flushing | 20.3% | 1.3% |
| Headache | 11.3% | 1.9% |
| Injection-site reaction | 5.4% | 0.5% |
How large is the effect?
A 2024 reanalysis in the Journal of Sex Research (Spielmans and Ellefson) examined the measurement properties of the RECONNECT efficacy outcomes and found questionable validity evidence for the primary scales in women with HSDD, no validity evidence for the categorical responder outcomes, and that results on 8 of the 11 outcomes specified on ClinicalTrials.gov had gone unpublished; on those, effect sizes ranged from nil to small. The paper is a critique, not a trial, but it is the most rigorous independent assessment in the evidence pack and it is why this profile describes bremelanotide's benefit as modest rather than large.
The grey-market “PT-141”
Vials sold online as PT-141 are not Vyleesi. They are unlicensed lyophilised peptide of unverified content, and — because bremelanotide and Melanotan II differ by one terminal group — cannot be assumed to be bremelanotide at all without mass-spectrometry confirmation. The approved product is a prescription autoinjector with a defined dose, a label, and a safety database; nothing about that transfers to a research-chemical listing. This profile is educational and is not guidance on obtaining or using any product.
Structure & chemistry
Molecular identity & reference confidence
Source-supported reference
Reference values are taken from the cited molecular record or curated profile. A database match is not independent laboratory verification; modifications, counter-ions, and formulations can change the measured mass.
- Molecular form
- Cyclic heptapeptide analogue of α-MSH (Ac-Nle-cyclo[Asp-His-D-Phe-Arg-Trp-Lys]-OH); described by IUPHAR as a stabilised, cyclic derivative of αMSH
- Species
- Not established by this molecular identity audit
- Termini (N / C)
- Not specified / Free acid — the des-amide form; the closely related Melanotan II carries a C-terminal amide
Average reference mass
Reference policy updated: 2026-10-05
- IUPHAR/BPS source snapshot · 2026-10-01
- PubChem molecular record · 2026-10-01
- Molecular formula
- C50H68N14O10
- Average reference mass
- ≈ 1,025.2
- Receptors
- Little selectivity across melanocortin receptors except MC2 (the ACTH receptor); the effect on sexual desire is attributed to MC3 and MC4 agonism in the central nervous system
- Backbone
- Cyclic heptapeptide analogue of α-MSH (Ac-Nle-cyclo[Asp-His-D-Phe-Arg-Trp-Lys]-OH); described by IUPHAR as a stabilised, cyclic derivative of αMSH
- C-terminus
- Free acid — the des-amide form; the closely related Melanotan II carries a C-terminal amide
- Status
- Approved in the US as Vyleesi (2019); not approved in Canada or the EU as of September 2026
Nle at position 1 replaces Met, D-Phe at position 4 and a lactam bridge between Asp and Lys side chains (the cyclisation) confer potency and stability; the N-terminus is acetylated.
- PubChem CID: 9941379
- IUPHAR ligand: 10408
- ChEMBL: CHEMBL2070241
- DrugBank: DB11653
- CAS RN: 189691-06-3
- UNII: 6Y24O4F92S
Chemistry values: curated profile, PubChem, IUPHAR/BPS Guide to Pharmacology · fetched 2026-10-01.
Clinical development snapshot
ClinicalTrials.gov lists 10 registered studies with “Bremelanotide” as an intervention (snapshot 2026-10-01). A registry footprint is not evidence of efficacy or approval.
| NCT | Title | Phase | Status | Updated |
|---|---|---|---|---|
| NCT06867835 | Single Dose of Vyleesi in Lactating Female Subjects to Measure the Concentration of Bremelanotide in Breast Mi | Phase 4 | completed | 2026-01-13 |
| NCT06565611 | A Phase 2 Study Evaluating the Co-Administration of Bremelanotide With Tirzepatide for the Treatment of Obesit | Phase 2 | active not recruiting | 2025-03-06 |
| NCT04943068 | A Phase 3, Bridging, Multicenter, Randomized, Double-blind, Placebo-controlled, Parallel-group Trial to Evalua | Phase 3 | completed | 2024-11-13 |
| NCT05709444 | A Phase IIb, Multicenter, Open-Label, Prospective Study of Bremelanotide in Diabetic Kidney Disease | Phase 2 | completed | 2024-10-17 |
| NCT04179734 | Role of the Melanocortin-4 Receptor in Hypoactive Sexual Desire Disorder | Phase 4 | completed | 2024-08-09 |
| NCT03973047 | Study to Evaluate Rate of Nausea in Healthy Premenopausal Female Subjects Treated With Single Dose of Bremelan | Phase 1 | completed | 2022-04-04 |
Bremelanotide (PT-141) — reconstitution calculator
Enter how much peptide is in the vial and how much diluent (e.g. bacteriostatic water) is added. The tool returns the resulting solution concentration — and, for any amount you type, the volume it corresponds to. This is educational arithmetic, not a dosing recommendation.
Reference form: Cyclic heptapeptide analogue of α-MSH (Ac-Nle-cyclo[Asp-His-D-Phe-Arg-Trp-Lys]-OH); described by IUPHAR as a stabilised, cyclic derivative of αMSHAverage reference mass: 1,025.2 Da
Enter an amount to see the volume it corresponds to.
Educational concentration mathematics only. This tool does not recommend a dose, amount, or protocol, and nothing here is medical advice. Many peptides are not authorized by Health Canada for human use — see our reconstitution and bacteriostatic-water guides for context.
Change log
Dated observations from the data pipeline (registry flags, trial footprints, identifiers) and editorial reviews of this profile.
- TrialsHighest registered trial phase moved from phase 3 to phase 4.
- Trials7 registered studies added on ClinicalTrials.gov (now 10).
- EditorialProfile content reviewed and updated by the editorial team.
FAQ about Bremelanotide (PT-141)
What is Bremelanotide (PT-141)?+
Bremelanotide, developed as PT-141, is a cyclic seven-residue analogue of α-melanocyte-stimulating hormone that activates melanocortin receptors, with its effect on sexual desire attributed to MC3 and MC4 signalling in the brain. The FDA approved it in 2019 as Vyleesi, an on-demand subcutaneous autoinjector for premenopausal women with acquired, generalised hypoactive sexual desire disorder. Nausea occurred in 40% of phase 3 participants, and a 2024 reanalysis found effect sizes from nil to small on most trial outcomes.
What Canadian product status is recorded for Bremelanotide (PT-141)?+
Canadian product status for Bremelanotide (PT-141) has not been verified in this profile. No verified record here does not mean no authorization exists. Status depends on the product, formulation and use; consult Health Canada's product records.
What is the typical length of Bremelanotide (PT-141)?+
Bremelanotide (PT-141) is commonly described as approximately 7 amino acids (Cyclic melanocortin-receptor agonist (approved medicine)).
What is PT-141?+
The development code for bremelanotide, a cyclic melanocortin-receptor agonist peptide approved by the FDA in 2019 as Vyleesi for hypoactive sexual desire disorder in premenopausal women.
Is PT-141 FDA approved?+
Bremelanotide (Vyleesi) is approved in the US. Grey-market vials labelled PT-141 are not the approved product.
How does bremelanotide work?+
It activates melanocortin receptors; its effect on sexual desire is attributed to MC3 and MC4 agonism in the brain, a mechanism unrelated to serotonin or dopamine drugs.
What are the side effects of bremelanotide?+
In phase 3, nausea in 40% of women (vs 1.3% placebo), flushing in 20%, headache in 11%, injection-site reactions in 5%; transient blood-pressure rises and rare liver-enzyme elevations are also described.
What is the difference between PT-141 and Melanotan II?+
They share a cyclic α-MSH-derived core; bremelanotide is the free-acid (des-amide) form and is an approved medicine, Melanotan II is the amide and is unlicensed.
How effective is bremelanotide?+
A 2024 independent reanalysis of the phase 3 trials found effect sizes from nil to small on most registered outcomes and questioned the validity of the primary scales.
Further reading
- ComparisonMelanotan I vs Melanotan II: An Educational ComparisonAn educational comparison of two melanocortin peptides—receptor selectivity (MC1R vs MC1R and MC4R), afamelanotide's narrow approval, and the unapproved status of research use.
- SafetyPeptide Safety and Risks: A Balanced Educational OverviewAn objective, balanced overview of what research does and does not establish about peptide risks—unknowns, purity and contamination concerns, and why unapproved compounds carry uncertainty. Not reassurance and not medical advice.
- FoundationsWhat Are Research Peptides? A Clear Educational GuideLearn what “research peptides” means, how they differ from approved peptide drugs, quality markers (COA, purity), and how to study them responsibly.
Related peptides
References & further reading
- 1.Hedlund (2004). PT-141 Palatin. Curr Opin Investig Drugs
- 2.Diamond et al. (2006). An effect on the subjective sexual response in premenopausal women with sexual arousal disorder by bremelanotide (PT-141), a melanocortin receptor agonist. J Sex Med
- 3.Dhillon et al. (2019). Bremelanotide: First Approval. Drugs
- 4.Edinoff et al. (2022). Bremelanotide for Treatment of Female Hypoactive Sexual Desire. Neurol Int
- 5.Clayton et al. (2022). Safety Profile of Bremelanotide Across the Clinical Development Program. J Womens Health (Larchmt)
- 6.Mayer et al. (2020). Bremelanotide: New Drug Approved for Treating Hypoactive Sexual Desire Disorder. Ann Pharmacother
- 7.Spielmans (2021). Re-Analyzing Phase III Bremelanotide Trials for "Hypoactive Sexual Desire Disorder" in Women. J Sex Res
- 8.Kingsberg et al. (2019). Bremelanotide for the Treatment of Hypoactive Sexual Desire Disorder: Two Randomized Phase 3 Trials. Obstet Gynecol
- 9.Spielmans & Ellefson (2024). Small Effects, Questionable Outcomes: Bremelanotide for Hypoactive Sexual Desire Disorder. Journal of Sex Research
- 10.LiverTox (2021). Bremelanotide. NIDDK
- 11.Medical Letter (2019). Bremelanotide (Vyleesi) for hypoactive sexual desire disorder. The Medical Letter on Drugs and Therapeutics
- 12.PubChem — Bremelanotide (CID 9941379)