VYLEESI / NDA 210557 / FDA 2019-06
PT-141 is the cyclic heptapeptide approved as the first central melanocortin agonist for premenopausal HSDD.
Bremelanotide acts in the hypothalamus, not on penile vasculature. The pivotal RECONNECT program enrolled 1,267 women across two identically designed Phase 3 trials. This is the published record — label, pharmacokinetics, adverse events, and the independent re-analyses that contextualize the effect size.
What is PT-141?
PT-141 is the laboratory designation for bremelanotide, a synthetic cyclic heptapeptide and non-selective melanocortin receptor agonist with principal therapeutic activity at MC4R in the hypothalamus [1][2]. The molecule was advanced by Palatin Technologies in the early 2000s as a clinical candidate for sexual dysfunction and received FDA approval in June 2019 under New Drug Application 210557 for hypoactive sexual desire disorder in premenopausal women [3][4]. The structure is Ac-Nle-cyclo[Asp-His-D-Phe-Arg-Trp-Lys]-OH — seven amino acids closed by a lactam bridge between aspartate and lysine that confers conformational and metabolic stability. Molecular formula C50H68N14O10, molecular weight 1025.2 Da, CAS 189691-06-3. The compound is the active metabolite of Melanotan II, minus the C-terminal amide, which shifts its selectivity profile toward MC4R-driven central effects and away from MC1R-driven generalized pigmentation [1].
The pharmacology is the headline. Unlike PDE5 inhibitors, which act peripherally on penile vasculature through the nitric oxide / cGMP axis, PT-141 modulates central nervous system pathways — the medial preoptic area, the paraventricular nucleus, and downstream dopaminergic relays through the ventral tegmental area — that regulate sexual desire and arousal [1][11][12]. That mechanism distinction is not academic. It is what allowed the compound to be developed for a desire-domain indication where no peripheral-vasodilator class had succeeded.
PT-141 (Bremelanotide): the melanocortin peptide
The PT-141 peptide is a synthetic analogue of alpha-melanocyte-stimulating hormone (alpha-MSH), the endogenous melanocortin that signals through five G-protein-coupled receptors (MC1R-MC5R). PT-141 binds all five but is most therapeutically relevant at MC4R, expressed densely in hypothalamic nuclei that govern energy balance, appetite, and sexual function [1][12]. The receptor potency order — MC1R > MC4R > MC3R > MC5R > MC2R — explains both the indication (MC4R agonism in mPOA-PVN circuits) and the principal adverse event (MC1R cross-activity on cutaneous melanocytes, producing focal hyperpigmentation) [4][5].
The Palatin-led pharmacology paper that first characterized PT-141 as a clinical candidate was published in Annals of the New York Academy of Sciences in 2003 [1]. The first preclinical behavioral evidence — selective increase in proceptive sexual solicitations in ovariectomized female rats at doses that did not alter receptive lordosis or general locomotion — appeared in PNAS in 2004 from Pfaus and colleagues [10]. The translational arc from rat solicitation to human Phase 3 took fifteen years.
What is PT-141 used for?
PT-141 is approved for acquired, generalized hypoactive sexual desire disorder (HSDD) in premenopausal women, administered as a 1.75 mg subcutaneous injection on an as-needed basis at least 45 minutes before anticipated sexual activity, with a maximum of one dose per 24 hours and eight doses per month [4][7]. The approved product is delivered through a single-use prefilled autoinjector. The indication, the dose, the timing window, and the frequency caps are all label-defined and trial-supported [3][4][7].
Off-label, the early intranasal formulation was studied in male erectile dysfunction in the 2000s, including a 2005 Urology paper from Diamond and colleagues reporting an additive erectile response when intranasal PT-141 at 7.5-10 mg was co-administered with sildenafil 25 mg in ED non-responders [9]. The intranasal program was halted by the FDA in 2007 over a blood-pressure signal, and the subcutaneous reformulation drove the eventual approval for the HSDD indication [4]. No male indication has been approved.
What the published record actually shows
Across the clinical development program, bremelanotide has been studied in more than 3,500 subjects across 43 completed studies, with the pivotal evidence anchored in two identically designed Phase 3 trials — Study 301 and Study 302, jointly known as RECONNECT — enrolling 1,267 premenopausal women with HSDD [3]. Both trials hit statistical significance on the co-primary endpoints: FSFI-D (the desire domain of the Female Sexual Function Index) and FSDS-DAO Item 13 (a personal-distress measure). The open-label extension carried exposure to roughly 76 weeks and produced no new safety signal [4][6].
Independent re-analysis has tempered the celebration. The Spielmans 2021 Journal of Sex Research paper argued that while statistical significance was achieved, the clinical magnitude of benefit was modest and sat below thresholds some authors consider meaningful, and dropout in the active arm exceeded placebo [14]. The most recent mechanistic evidence — a 2022 JCI fMRI crossover study in 31 premenopausal HSDD women — confirmed that a single 1.75 mg subcutaneous dose increased self-reported sexual desire up to 24 hours post-administration (P=0.007) and modulated cerebellar, supplementary motor area, and secondary somatosensory cortex activity during visual erotic stimuli [17]. That is the first imaging-level confirmation of central action in the target population.
See the full PT-141 dosage, the PT-141 side effects, and the PT-141 references and citations.