Most sexual-function medicines act on blood vessels. PT-141 is studied because it acts on receptors in the brain instead, and one formulation became a registered medicine.
PT-141 · Cyclic melanocortin receptor agonist
Sexual response involves a central component, desire and arousal processed in the brain, and a vascular component, blood flow to genital tissue. These can fail separately. PT-141 is investigated for the central side, through melanocortin receptors, which is why researchers care. Evidence includes human trials, and in the United States one product is approved for a narrowly defined condition in women.
PT-141, generic name bremelanotide, is a synthetic cyclic peptide of seven amino acids derived from alpha-melanocyte-stimulating hormone. It is an agonist, a molecule that activates a receptor, at the melanocortin receptors, a family of five cellular receivers numbered MC1R to MC5R that are involved in pigmentation, energy balance and, in the brain, sexual behaviour. Its history runs through Melanotan II: bremelanotide differs from that compound at one end of the molecule, a free carboxylic acid where Melanotan II carries an amide, and was identified during early studies of that compound (Molinoff et al., 2003).
In the laboratory, bremelanotide activates several receptor subtypes with the order of potency MC1R, MC4R, MC3R, MC5R, MC2R. The working hypothesis is that MC4R signalling in the hypothalamus is the relevant pathway for sexual desire. That is investigated receptor activity, not an established clinical mechanism: the US prescribing information states that the mechanism by which the medicine improves the approved condition is unknown (FDA label, 2019, sections 11 and 12).
Early human work was in men. A double-blind crossover study gave the parent compound Melanotan II subcutaneously to men with psychogenic erectile dysfunction and measured erections and reported desire (Wessells et al., 1998). Bremelanotide itself was then studied intranasally in premenopausal women with sexual arousal disorder, measuring self-reported response (Diamond et al., 2006). The intranasal route was abandoned after blood-pressure findings, and the programme moved to subcutaneous injection.
The decisive evidence is RECONNECT, two randomised, placebo-controlled phase 3 trials in premenopausal women with hypoactive sexual desire disorder, measuring change in a validated desire score and in distress over 24 weeks (Kingsberg et al., 2019). On that basis the US FDA approved Vyleesi (bremelanotide injection) in June 2019 for premenopausal women with acquired, generalised hypoactive sexual desire disorder. The label limits the use: it is not indicated for postmenopausal women or for men, and not indicated to enhance sexual performance. Nausea was the most common adverse effect in the trials, and transient blood-pressure increases were recorded.
The approval covers one condition in one population with one subcutaneous formulation; it is not evidence for male sexual function, for postmenopausal women or for performance in anyone. The male erectile studies are small, older and partly used the parent compound. Which melanocortin receptor subtype, in which brain region, produces the clinical effect remains unresolved, and the same receptor family also affects blood pressure and skin pigmentation. Long-term data beyond the trial windows are limited, and these findings do not establish equivalent quality, safety or clinical effects for non-registered material.
Bremelanotide is not an approved medicine in Australia and is not separately listed in the Poisons Standard (June 2026). In the United States, Vyleesi (bremelanotide injection) is FDA-approved for premenopausal women with acquired, generalised hypoactive sexual desire disorder, and is expressly not indicated for men, postmenopausal women or enhancing sexual performance.
Sources and status checked 2026-09-22
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