PT-141

Overview

PT-141, known generically as bremelanotide, is a synthetic cyclic heptapeptide that activates melanocortin receptors, with its clinically relevant activity attributed to MC4R signaling in the central nervous system. It was engineered from alpha-melanocyte-stimulating hormone and is an active metabolite of Melanotan II, differing at the C-terminus in that it lacks the C-terminal amide (carrying a C-terminal hydroxyl instead). Unlike PDE5 inhibitors, which act on vascular smooth muscle, bremelanotide has been studied for its effects on the brain circuitry that governs sexual desire and arousal. In June 2019 the U.S. FDA approved it as Vyleesi, a 1.75 mg on-demand subcutaneous injection, for acquired, generalized hypoactive sexual desire disorder (HSDD) in premenopausal women, making it one of the most clinically characterized peptides in the melanocortin class. Its approval rested on two large Phase 3 trials (the RECONNECT program) and multiple earlier Phase 2 studies. Published research has also examined melanocortin signaling in areas such as energy balance, inflammation, and hemorrhagic shock, though those applications remain research-use-only. Because it is an approved finished drug for one specific indication, bremelanotide sits apart from the compounding-bulks conversation surrounding many other research peptides, including the compounds on the FDA Pharmacy Compounding Advisory Committee's July 2026 docket.

Mechanism of action

Bremelanotide is a non-selective melanocortin-receptor agonist that engages MC1R, MC3R, MC4R, and MC5R (but not MC2R), acting principally as an MC3R and MC4R agonist. Its therapeutically relevant activity is attributed to MC4R activation in hypothalamic and limbic regions of the brain. It retains the conserved His-Phe-Arg-Trp pharmacophore of alpha-MSH within a lactam-bridged cyclic structure that constrains its conformation and improves receptor engagement and metabolic stability relative to the linear native hormone. By modulating central melanocortin tone, it is thought to influence dopaminergic and other neural pathways involved in sexual motivation and arousal, a mechanism distinct from the peripheral vasodilatory action of PDE5 inhibitors. Activation of MC1R accounts for its melanocortin-typical effect on melanocytes, which underlies the pigmentation-related observations seen in the literature. MC3R and MC4R signaling has also been implicated in appetite, energy homeostasis, and cardiovascular regulation, consistent with the transient increases in blood pressure and reductions in heart rate documented after dosing in clinical studies.

What published research has examined

The best-established, FDA-approved application is acquired, generalized hypoactive sexual desire disorder in premenopausal women, supported by the RECONNECT Phase 3 program and earlier trials in both women and men. Beyond this indication, published research has explored melanocortin pathway agonism in preclinical and early clinical contexts including erectile function, female sexual arousal, energy balance and obesity-related signaling, anti-inflammatory effects, and resuscitation in models of hemorrhagic and ischemic shock, where related melanocortin compounds have been investigated. These non-approved directions remain research-use-only and, in most cases, preclinical or early-stage. Because the parent melanocortin system touches pigmentation, appetite, cardiovascular tone, and neuroinflammation, the peptide is also used as a pharmacological tool to probe MC3R and MC4R biology. It is important to distinguish the single narrow approved use from the broader, less-mature exploratory literature.

Safety considerations in the literature

In the RECONNECT Phase 3 trials and the approved product labeling, the most frequently reported adverse reactions were nausea (reported by roughly 40% of patients over repeated dosing, and prompting anti-emetic use or discontinuation in a subset), flushing, injection-site reactions, headache, and vomiting. The label documents a transient increase in blood pressure and a reduction in heart rate after each dose, typically resolving within about 12 hours; for this reason the product is not recommended in people at high cardiovascular risk, and labeling limits how often dosing may occur to mitigate more pronounced pressure effects. Focal hyperpigmentation of the face, gingiva, and breasts was reported in about 1% of patients, with higher risk in individuals with darker skin and with more frequent dosing, and resolution after discontinuation was not confirmed in all cases. These findings are drawn from regulated clinical trials and the FDA label; the safety of unapproved applications, higher exposures, or non-pharmaceutical-grade material has not been established in the published literature.

Key published studies

Regulatory status

Current status: FDA Approved (Vyleesi); other applications RUO. FDA Approved. PepSense tracks FDA filings and updates this record as the regulatory picture changes. See the FDA PCAC tracker for the July 2026 vote and what happens next.

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