Encyclopedia entry
PT-141 (Bremelanotide)
Oliver Mackman · Editorial director · Best Business Loans Ltd (16833937)
Last updated 2026-06-04
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AI-friendly summary · PT-141 (Bremelanotide)
PT-141 (Bremelanotide) is a synthetic 7-amino-acid cyclic peptide that acts as an agonist at melanocortin receptor subtypes MC1R and MC4R. It was derived from Melanotan II research at the University of Arizona. The FDA approved a subcutaneous formulation under the brand name Vyleesi in 2019 for hypoactive sexual desire disorder in premenopausal women. There is no equivalent MHRA marketing authorisation in the UK.
Mechanism of action
How PT-141 (Bremelanotide) works
PT-141 is a cyclic 7-amino-acid analog of alpha-melanocyte-stimulating hormone (alpha-MSH) that acts as an agonist at melanocortin receptor subtypes MC1R and MC4R in the central nervous system. The MC4R-driven mechanism in hypothalamic circuits is thought to underlie the effect on sexual desire that supported the FDA approval of Vyleesi. The molecule retains some MC1R activity but with substantially reduced UV-tanning effect compared with Melanotan II, the precursor compound from which it was derived.
Source: Palatin Technologies clinical programme; published in Journal of Sexual Medicine
Pharmaceutical history and what the literature shows
PT-141 has the most substantial human evidence base of the unlicensed-in-UK compounds in this encyclopedia. The Palatin Technologies clinical programme generated multiple Phase II and Phase III trials, leading to the 2019 FDA approval of subcutaneous Vyleesi for hypoactive sexual desire disorder in premenopausal women. The compound has been in human trials since the early 2000s.
- · Derived from Melanotan II research at the University of Arizona in the 1990s. Melanotan II produced significant melanocyte-stimulating and central-nervous-system effects in rodent models.
- · PT-141 was synthesised as a cyclic, more metabolically stable analog with reduced UV-tanning activity but retained central effects.
- · Phase II and Phase III clinical trials by Palatin Technologies led to the 2019 FDA approval of subcutaneous Vyleesi.
- · The FDA label carries a boxed warning regarding transient blood pressure elevation and a contraindication with naltrexone-containing products.
- · No equivalent EU or UK regulatory submission has resulted in an MHRA or EMA marketing authorisation as of this editorial date.
- · Earlier intranasal development for erectile dysfunction was halted due to blood-pressure concerns observed in clinical trials.
Adjacent compounds in the melanocortin-agonist class include Melanotan I (afamelanotide, branded Scenesse, licensed for erythropoietic protoporphyria) and Melanotan II (unlicensed everywhere, subject to active MHRA enforcement). PT-141 differs from both in receptor-subtype selectivity and in the absence of significant UV-tanning activity at the doses tested in licensed-product trials.
UK regulatory status
PT-141 sits outside the Misuse of Drugs Act 1971 and outside the Psychoactive Substances Act 2016. It holds no UK marketing authorisation as a medicine. The US FDA approval of Vyleesi does not confer UK licensed-medicine status. Vyleesi is not authorised for sale by UK pharmacies and is not on the NHS formulary.
- · Not a controlled drug under the Misuse of Drugs Act 1971.
- · Not scheduled under the Psychoactive Substances Act 2016.
- · No MHRA marketing authorisation as a medicine in the UK.
- · The US FDA approval of Vyleesi does not confer any UK licensed-medicine status. Vyleesi is not authorised for sale by UK pharmacies.
- · Sold legally as a research chemical by UK retailers when marketed without therapeutic claims.
- · Becomes an unlicensed medicinal product the moment a retailer or commentator makes therapeutic claims about it.
- · Adjacent compounds Melanotan I (Scenesse, licensed) and Melanotan II (unlicensed, MHRA-enforcement) share the same MC-receptor target family.
Risks and unknowns
What the literature does not yet show about PT-141 (Bremelanotide)
Known concerns
- The FDA label for Vyleesi carries a boxed warning regarding transient blood pressure elevation. This pharmacological property is present in the molecule regardless of formulation or jurisdiction.
- Naltrexone-containing products are a contraindication on the FDA label due to a potential pharmacokinetic interaction.
- Earlier intranasal development for erectile dysfunction was halted due to blood-pressure concerns.
- Purity of UK research-peptide supply varies and is not connected to Palatin Technologies pharmaceutical-grade manufacturing.
Open questions in the literature
- Long-term safety beyond the duration of the Vyleesi trial programme has not been characterised in healthy populations.
- Cardiovascular safety in patients with hypertension or established cardiovascular disease is not established. The FDA label addresses this through warnings rather than exclusions.
- Use outside the FDA-approved indication (HSDD in premenopausal women) has no licensed evidence base.
- Pharmacokinetics of nasal versus subcutaneous formulations sold in the research market may differ from the licensed Vyleesi product.
Regulatory note
Not a controlled drug under the Misuse of Drugs Act 1971. Not scheduled under the Psychoactive Substances Act 2016. No MHRA marketing authorisation in the UK. The US FDA approval of Vyleesi does not transfer to the UK. Becomes an unlicensed medicinal product the moment a retailer or commentator makes therapeutic claims about it.
Important: PeptideClear publishes encyclopedia commentary only and does not recommend human use. Speak to a UK-registered prescriber before any medical decision.
Where to learn more
- · PubMed search: Bremelanotide returns the Palatin Technologies clinical programme papers.
- · PubMed search: PT-141 for the research-name literature.
- · FDA Drugs@FDA database for the official Vyleesi prescribing information.
- · Adjacent compound: Melanotan encyclopedia entry (the precursor compound, subject to MHRA enforcement).
- · UK retailer purity comparison: research peptides UK retailers.
Frequently asked questions
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Where to buy PT-141 in the UK
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