CLINICAL EVIDENCE DIGEST · MELANOCORTIN MC3R + MC4R AGONIST
PT-141 is the melanocortin research peptide bremelanotide — read here with its tolerability first.
A genuinely approved drug with a frontier mechanism: it works on the brain's desire circuitry, not the blood vessels. This site reads the cited trial evidence, flags the honest gaps, and fences off the unverified field reports — so a forum anecdote is never mistaken for a Phase 3 endpoint.
The short version
Here is PT-141 in plain English. It is a tiny synthetic peptide — the research name for a drug called bremelanotide — and it acts on switches in the brain (melanocortin MC3R/MC4R receptors — brain receptors that influence sexual desire, appetite, and skin pigment) rather than on blood flow. In June 2019 the US FDA approved it for exactly one use: low sexual desire that causes real personal distress in premenopausal women, a condition doctors call HSDD (hypoactive sexual desire disorder). In the big trials it helped — but modestly — and the most common cost was nausea. Everything else you may read about PT-141, including use in men, is off-label and still early. This page is the map; the cited detail lives on the pages it links to.
What Is PT-141?
PT-141 is the research designation for bremelanotide, a synthetic cyclic heptapeptide (a chain of seven amino acids joined in a ring) and a melanocortin receptor agonist — a molecule that switches on the brain's melanocortin receptors [1]. It is a laboratory-built analogue of alpha-MSH (alpha-melanocyte-stimulating hormone — a natural signalling peptide the body makes from a precursor protein called POMC) [8].
Its identity is fully documented. Bremelanotide carries CAS number 189691-06-3, FDA UNII 6Y24O4F37N, DrugBank ID DB12420, molecular formula C50H68N14O10, and a molecular weight of 1025.2 Da [6]. The US approval sits under NDA 210557, granted June 21, 2019 [7]. PT-141 and bremelanotide are not two compounds — they are the same molecule under its research code and its international nonproprietary name (INN).
What makes it interesting is the address it targets. Most familiar treatments for sexual problems act on the plumbing — the blood vessels. PT-141 acts a layer earlier, on the neural circuitry of desire itself. That is the forward-looking part of this story, and it is real. The honest part — the modest effect size and the tolerability cost — is on this site too, read first rather than buried.
PT-141 Peptide: Structure and Identity
The PT-141 peptide is a seven-amino-acid ring: sequence Ac-Nle-cyclo[Asp-His-D-Phe-Arg-Trp-Lys]-OH, closed by a lactam bridge between the Asp and Lys side chains [6]. "Cyclic" matters here — folding a peptide into a ring makes it far more stable than the loose, linear melanocortin peptides the body breaks down quickly [6].
Structurally it is a close relative of melanotan II, with one deliberate change: the C-terminal amide is replaced by a carboxylic acid [6]. That single substitution is part of what tunes its behaviour toward the central nervous-system receptors that govern desire. The finished pharmaceutical, bremelanotide injection, is the approved form of this peptide [7]; material sold under the label "PT-141 research chemical" is a laboratory reagent with no regulatory oversight of its identity, purity, or concentration, and is not the approved drug [6].
What Does PT-141 Do?
PT-141 activates central melanocortin receptors — chiefly the melanocortin 4 receptor (MC4R), with secondary action at MC3R — concentrated in the hypothalamus and limbic system, the brain's motivation hubs [1]. By stimulating MC4R in circuits such as the medial preoptic area, it is thought to engage the dopamine signalling that drives appetitive, desire-led sexual behaviour [3].
The preclinical signal is clear and reproducible. In rats and nonhuman primates, systemic PT-141 produced erections and lit up hypothalamic neurons, consistent with a brain-level mechanism [1]. In female rats it selectively increased solicitational (desire-led) behaviour without changing reflexive responses or general movement — the first drug reported to act on appetitive female sexual behaviour [2]. In premenopausal women with HSDD, it improved sexual desire and reduced the distress that low desire caused [3].
What it does not do is also worth stating plainly: it does not raise testosterone and it does not work like the blood-flow drugs. Those two points are the most common misconceptions about the compound — both addressed in the common questions about PT-141, with the full PT-141 mechanism of action on the research page.
What PT-141 Is Used For
Bremelanotide is FDA-approved for exactly one indication: acquired, generalized hypoactive sexual desire disorder (HSDD — persistent, distressing low sexual desire not explained by another cause) in premenopausal women [7]. That approval rests on two Phase 3 trials and a year-long safety extension [3][4].
Every other use is off-label and investigational. The early erectile-response data in men is real but early-phase, not established or approved [1]; the lens of PT-141 for men has its own page covering the off-label erectile research in full. Use in postmenopausal women, in erectile dysfunction, and for general sexual "performance" is outside the approval and not supported by it [9].
This is a transparency-first reading, so the boundaries are drawn before the promise. The mechanism is genuinely novel and the approval is genuine — and the approval covers one population, one indication, one dose. The cited detail on benefits, on how PT-141 works, on PT-141 dosage in the research, and on the cardiovascular and hyperpigmentation cautions follows on the linked pages.