Summary

PT-141, also known as bremelanotide, is a synthetic peptide analogue of alpha-melanocyte-stimulating hormone (α-MSH) that acts as a melanocortin receptor agonist. It was developed from the tanning peptide Melanotan II after researchers observed an unexpected effect on sexual arousal. Unlike PDE5 inhibitors such as sildenafil, PT-141 acts centrally on the nervous system rather than on vascular mechanics. An injectable formulation was FDA-approved in 2019 under the brand name Vyleesi for the treatment of premenopausal women with acquired, generalised hypoactive sexual desire disorder (HSDD). It is not licensed by the MHRA in the UK for this indication.

Mechanism

PT-141 is a non-selective agonist of melanocortin receptors, with primary affinity for MC1R, MC3R, MC4R, and MC5R. Unlike PDE5 inhibitors that act peripherally on vascular smooth muscle, PT-141 acts centrally — activating melanocortin receptors in the hypothalamus, which are involved in regulating sexual arousal and desire. The MC4R receptor in particular has been implicated in the mediation of sexual behaviour. This central mechanism explains why PT-141 does not require direct sexual stimulation to produce its effects. The melanocortin pathway also influences pigmentation (via MC1R), appetite, and inflammation, which accounts for the side-effect profile including nausea, flushing, and transient blood pressure elevation.

Evidence base

Pivotal Trials

RECONNECT trials (Phase 3): Two double-blind, placebo-controlled, randomised trials enrolled a combined total of approximately 1,247 premenopausal women with HSDD. Participants self-administered bremelanotide 1.75 mg subcutaneously on demand. In the pooled analysis, 25.0% of bremelanotide-treated women met the threshold for meaningful improvement in desire (≥1.2-point increase in FSFI desire domain) versus 16.9% on placebo. Nausea (40%), flushing (20%), and injection site reactions (12%) were the most common adverse events.

Male erectile dysfunction (Phase 2): An earlier study in men with ED who were non-responsive to PDE5 inhibitors showed improvement in erectile function following intranasal bremelanotide. However, development for male ED was discontinued due to elevations in blood pressure observed with the intranasal formulation.

Systematic Reviews

A 2023 systematic review and meta-analysis of pharmacological treatments for female sexual dysfunction noted that bremelanotide demonstrated modest but statistically significant improvements in desire compared with placebo, though the clinical meaningfulness of the effect size has been debated.

Protocols

The FDA-approved dosing for Vyleesi is 1.75 mg subcutaneously, administered approximately 45 minutes before anticipated sexual activity, with a maximum of one dose per 24 hours and no more than eight doses per month. In research peptide contexts, discussed amounts typically range from 0.5–2 mg per administration. The peptide is reconstituted with bacteriostatic water and administered subcutaneously. These figures are provided for research reference only; PT-141 is not licensed in the UK.

Bremelanotide (PT-141) is not licensed by the MHRA in the UK. It is an FDA-approved prescription medicine in the US (Vyleesi), meaning it would be treated as a prescription-only medicine if imported. As a research peptide sold for laboratory use, it occupies a legal grey area — purchasable for legitimate research but not for human consumption without appropriate regulatory authorisation.

Vendor notes

PT-141 is stocked by several UK research peptide suppliers. Researchers should verify that vendors provide independent COAs confirming peptide identity and purity (≥98%). Because bremelanotide is an approved medicine in some jurisdictions, quality and provenance are particularly important.

References

  1. Kingsberg SA, Clayton AH, Pfaus JG. Bremelanotide for the Treatment of Hypoactive Sexual Desire Disorder: Two Randomized Phase 3 Trials. J Sex Med. 2019;16(9):1409-1418. doi:10.1016/j.jsxm.2019.06.014
  2. Clayton AH, Lucas J, Jordan R, et al. Bremelanotide for Female Sexual Dysfunctions in Premenopausal Women: A Randomized, Placebo-Controlled, Double-Blind Study. J Sex Med. 2023;20(1):46-55. doi:10.1093/jsxmed/qdac023
  3. Molinoff PB, Shadiack AM, Earle D, Diamond LE, Quon CY. PT-141: a melanocortin agonist for the treatment of sexual dysfunction. Ann N Y Acad Sci. 2003;994:96-102. doi:10.1111/j.1749-6632.2003.tb03168.x
  4. Diamond LE, Earle DC, Rosen RC, Willett MS, Molinoff PB. Double-blind, placebo-controlled evaluation of the safety, pharmacokinetic and pharmacodynamic effects of intranasal PT-141 in healthy females. J Sex Med. 2006;3(Suppl 5):278. doi:10.1111/j.1743-6109.2006.00315.x
  5. US Food and Drug Administration. Vyleesi (bremelanotide injection) Prescribing Information. AMAG Pharmaceuticals; 2019. Available at: https://www.accessdata.fda.gov/drugsatfda_docs/label/2019/210557s000lbl.pdf