RESEARCH DIGEST / BREMELANOTIDE
PT-141 is the research code for bremelanotide, a melanocortin agonist approved for one use only.
An FDA-approved drug (2019) for low sexual desire in premenopausal women. Every other use — in men, for erectile dysfunction, for performance — is off-label. Here is what the trials and the label actually establish, cited line by line.
The short version
PT-141 is bremelanotide, a small synthetic peptide. It works in the brain, not the bloodstream: it switches on melanocortin receptors (brain switches that influence sexual desire, appetite, and skin pigment) in circuits tied to wanting sex. The US Food and Drug Administration approved it in 2019 — but only for one thing: acquired, generalized HSDD (hypoactive sexual desire disorder, meaning persistently low sexual desire that causes real personal distress) in premenopausal women. Using it in men, for erections, or to boost performance is off-label, and the evidence there is early-stage. This page covers what the studies measured, and nothing more.
What PT-141 is, in one line
PT-141 is the original research designation for bremelanotide, a synthetic cyclic heptapeptide — a chain of seven amino acids joined in a ring — built as an analogue of alpha-MSH (alpha-melanocyte-stimulating hormone, a natural brain peptide that activates melanocortin receptors) [1]. The ring closes through a lactam bridge, a chemical clasp that makes the molecule more stable than the straight-chain melanocortins it was modeled on. Its formula is C50H68N14O10, molecular weight 1025.2 Da, CAS 189691-06-3, sequence Ac-Nle-cyclo[Asp-His-D-Phe-Arg-Trp-Lys]-OH.
"PT-141" and "bremelanotide" are the same molecule. PT-141 is the lab code; bremelanotide is the international nonproprietary name (INN) of the approved drug. The US prescribing information lists the approval as NDA 210557, granted June 21, 2019 [6].
PT-141 peptide: a synthetic melanocortin agonist
The PT-141 peptide belongs to a defined drug class: melanocortin (MC3R/MC4R) receptor agonist. Melanocortin receptors are a family of five G-protein-coupled receptors (MC1R through MC5R); the central-nervous-system subtypes, MC3R and MC4R, are the relevant targets here [1]. By stimulating MC4R in hypothalamic circuits, PT-141 engages dopamine-linked pathways associated with sexual motivation [1]. This is the brain-side route — distinct from the peripheral, blood-flow route that PDE-5 inhibitors (a separate drug class, e.g. sildenafil) take.
A practical consequence of being a melanocortin agonist: PT-141 also touches MC1R in the skin, which is why repeated frequent dosing has been linked to hyperpigmentation — darkening of skin, gums, or breasts [12]. And because MC4R sits in appetite circuits too, high-frequency research dosing produced caloric-intake effects, a pharmacological footnote, not an approved use [6].
PT-141 as a melanocortin receptor agonist
Calling PT-141 a melanocortin receptor agonist is the most precise one-line description of how it acts. An agonist is a molecule that switches a receptor on; a melanocortin receptor agonist switches on the MC1R-MC5R family that responds to alpha-MSH and related peptides [1]. PT-141 targets the central MC3R and MC4R subtypes. That central action — in the hypothalamus and limbic system rather than on blood vessels — is the entire reason its sexual-function profile differs from the peripheral PDE-5 class [1]. The two RECONNECT Phase 3 trials and the mechanistic neuroimaging work both trace the effect back to this central melanocortin engagement [3][5].
What the human record shows
Two identical Phase 3 randomized controlled trials, run together as RECONNECT (n=1267 premenopausal women with HSDD), met both coprimary endpoints: bremelanotide 1.75 mg subcutaneous as-needed improved sexual desire (integrated FSFI-desire +0.35, P<.001) and reduced desire-related distress (integrated FSDS-DAO item 13 -0.33, P<.001) versus placebo over 24 weeks [3]. FSFI and FSDS are the standard questionnaires trials use to score sexual desire and the distress low desire causes. A 52-week open-label extension (684 women) sustained those gains with no new safety signals [4].
The effect is statistically real and clinically modest — that honest distinction matters, and critical re-analyses have pressed exactly that point [3]. A separate fMRI study (n=31) gave the mechanism a picture: MC4R agonism increased desire for up to 24 hours and altered how the brain processed erotic stimuli [5]. Read the RECONNECT Phase 3 trials in full on the research page.
PT-141 for men, and the tolerability question
The approval is for women. But PT-141's earliest human work was in men: systemic administration produced dose-dependent erectile activity, including in some sildenafil non-responders [1][7]. That use is off-label and investigational — never approved — and a 2024 Phase 2 program is now studying bremelanotide co-administered with a PDE-5 inhibitor in non-responders [14]. The full picture, including the discontinued intranasal route and the PDE-5-combination logic, lives on PT-141 for men.
Tolerability is the other half of the story, and it is not buried here. Nausea is common (~40% over long-term use) and the leading reason participants stopped; flushing (~21%) and headache (~12%) follow [4]. A transient rise in blood pressure is documented, which is why the label contraindicates use in uncontrolled hypertension or known cardiovascular disease [6]. The honest tolerability picture — clinical data and clearly-labeled community reports kept apart — is laid out under PT-141 side effects.
Material sold as "PT-141 research chemical" is laboratory material, not the approved finished drug, and sits entirely outside the pharmaceutical-approval framework — no oversight of identity, purity, or concentration. This site summarizes the published record; it recommends no dose to anyone.