TL;DR: PT-141 (bremelanotide) is a synthetic cyclic peptide analogue of alpha-melanocyte-stimulating hormone, studied as an agonist at the melanocortin MC3R and MC4R receptors with documented CNS-mediated activity. Its pharmaceutical form, Vyleesi, received FDA approval in 2019 following two Phase 3 RECONNECT trials. Research-grade PT-141 is a separate, non-approved compound subject to full research-use classification. WADA status: prohibited.
Research-Use Disclaimer: This article is for educational and research reference purposes only. PT-141 (bremelanotide) in research-grade form is not approved by the FDA for human use. This content does not constitute medical advice, does not recommend or endorse human administration of any research compound, and does not describe protocols for personal use. All study findings described below refer to published peer-reviewed research. For adults 21+ with a research interest only.
What Is PT-141 (Bremelanotide)? Definition and Origins
PT-141, known in the pharmaceutical literature as bremelanotide, is a synthetic cyclic heptapeptide, a seven-amino-acid chain, derived as a structural analogue of alpha-melanocyte-stimulating hormone (α-MSH), the endogenous neuropeptide produced from the precursor protein pro-opiomelanocortin (POMC). Its chemical designation is cyclo-[Nle4, D-Phe7]-α-MSH(4–10), and it shares a core sequence with the earlier research compound Melanotan II.
The distinction between PT-141/bremelanotide and Melanotan II is structurally meaningful: bremelanotide is a direct metabolite of Melanotan II, formed by the loss of the C-terminal amide. In the peer-reviewed development review published in Drugs by Dhillon and Keam (2019), the authors document that this structural modification eliminated the melanogenic (skin-tanning) activity associated with Melanotan II while retaining the compound’s high-affinity binding at melanocortin receptor subtypes MC3R and MC4R, the receptors implicated in its CNS-mediated pharmacological profile. The compound was developed by Palatin Technologies under the research designation PT-141 before entering clinical trials as bremelanotide, and subsequently out-licensed to AMAG Pharmaceuticals for North American commercialization.
How Does PT-141 Work? The MC3R / MC4R Receptor Mechanism
PT-141 (bremelanotide) produces its documented pharmacological effects by acting as an agonist at two members of the melanocortin receptor family, MC3R (melanocortin type 3 receptor) and MC4R (melanocortin type 4 receptor). Both are G protein-coupled receptors (GPCRs) expressed in the central nervous system, with MC4R particularly concentrated in the hypothalamus, brainstem, and limbic structures. This CNS localization distinguishes bremelanotide’s mechanism from compounds that act peripherally on vascular or gonadal tissue.
What Does MC4R Agonism Produce in the CNS?
MC4R is one of five known melanocortin receptor subtypes encoded in the human genome. In addition to its roles in energy homeostasis and appetite regulation, MC4R is expressed in brain regions associated with motivational and autonomic processes. A 2006 Phase 2 randomized controlled trial by Diamond et al., published in the Journal of Sexual Medicine, documented that a single intranasal dose of bremelanotide produced significantly more self-reported changes in subjective response compared to placebo in 18 premenopausal subjects with a diagnosed sexual arousal disorder, and characterized the mechanism as operating through MC3R and MC4R agonism modulating brain pathways involved in the autonomic sexual response, distinct from the peripheral vascular mechanism of phosphodiesterase-5 inhibitors. This CNS pathway emphasis is consistent with the compound’s receptor pharmacology: unlike peripherally acting vasodilators, bremelanotide targets hypothalamic and limbic receptor populations that are upstream of downstream physiological responses.
The Relationship Between MC4R Agonism and Blood Pressure
MC4R agonism has a documented cardiovascular correlate: transient increases in blood pressure. A randomized, double-blind, placebo-controlled ambulatory blood pressure monitoring trial by White et al. (2017), published in the Journal of Hypertension, enrolled 397 subjects across three dose levels of bremelanotide and found that bremelanotide produced statistically significant, dose-dependent increases in systolic blood pressure of 2.4–3.1 mmHg above placebo, accompanied by reductions in heart rate, during the 0–4 hour post-dose interval, with peak increases typically lasting less than 15 minutes. The authors noted that this cardiovascular signal, a reflex bradycardia pattern consistent with MC4R-mediated sympathetic activation, was one of the key findings that informed blood pressure monitoring requirements in the subsequent larger Phase 3 trials. This is not a secondary or incidental observation: the MC4R receptor’s role in autonomic regulation means cardiovascular effects are mechanistically linked to the same receptor target responsible for the compound’s studied primary effects.
A comprehensive review by Bardhan et al. (2025) in Diseases, covering the genetics and pharmacology of melanocortin receptor subtypes, contextualizes the broader melanocortin receptor family, noting that MC4R mutations are associated with monogenic obesity in humans, and that the FDA has approved multiple melanocortin agonists targeting different receptor subtypes for distinct indications, confirming bremelanotide’s place within a pharmacologically validated receptor class.
What Does the Bremelanotide Research Show?
The RECONNECT Phase 3 Trials
The most rigorous peer-reviewed evidence for bremelanotide’s pharmacological activity in human subjects comes from the two identically designed RECONNECT Phase 3 trials, published by Kingsberg et al. in Obstetrics and Gynecology in 2019. These multicenter, randomized, double-blind, placebo-controlled studies (ClinicalTrials.gov NCT02333071 and NCT02338960) enrolled 1, 247 subjects randomized 1:1 to bremelanotide 1.75 mg subcutaneous or placebo for 24 weeks. Both studies demonstrated statistically significant improvements in co-primary efficacy endpoints: Female Sexual Function Index desire domain score (Study 301: +0.30, P<0.001; Study 302: +0.42, P<0.001) and Female Sexual Distress Scale-Desire/Arousal/Orgasm Item 13 (Study 301: −0.37, P<0.001; Study 302: −0.29, P=0.005). Treatment-emergent adverse events, nausea (≈40%), flushing (≈20%), and headache (≈11%), were substantially more common in the bremelanotide arm than placebo.
Safety Profile Across the Clinical Program
A systematic review of bremelanotide’s safety data across the full clinical development program (43 completed studies, approximately 3, 500 subjects) was published by Clayton et al. (2022) in the Journal of Women’s Health. The review documented that the most common adverse events in the integrated double-blind Phase 3 population (n=1, 247) were nausea (40.0% vs. 1.3% placebo), flushing (20.3% vs. 1.3%), headache (11.3% vs. 1.9%), and injection site reactions (5.4% vs. 0.5%). No deaths were attributed to bremelanotide. Focal hyperpigmentation, a mechanistically expected consequence of melanocortin receptor activation, occurred in more than one-third of subjects in studies involving up to 16 consecutive daily doses, though was rare at label-recommended dosing intervals. Transient blood pressure increases were confirmed across the program, leading to cardiovascular monitoring recommendations in the prescribing label.
RECONNECT Subgroup Analyses
A pre-specified subgroup analysis of the RECONNECT pooled population by Simon et al. (2022), published in the Journal of Women’s Health, evaluated efficacy by age, weight, BMI, baseline bioavailable testosterone quartile, and hormonal contraceptive use. Bremelanotide achieved statistically significant improvements in desire and distress reduction across all age, weight, and BMI subgroups, and across all baseline testosterone quartiles, with few exceptions, reinforcing the MC4R-mediated CNS mechanism as a pathway operating with relative independence from circulating androgen levels. This finding is pharmacologically relevant because it suggests the documented effect operates upstream of the hormonal axes that typically drive androgen-dependent responses.
Early-Phase Receptor Pharmacology and Clinical Framing
A 2020 systematic review by Mayer and Lynch published in Annals of Pharmacotherapy, reviewing Phase 2 and Phase 3 trial data in context of bremelanotide’s FDA approval, characterized the compound as a melanocortin 4 receptor agonist whose Phase 3 trials met statistical significance for their co-primary endpoints, while noting that the clinical magnitude of effect was modest, a characterization consistent with the RECONNECT trial effect sizes, which were statistically significant but numerically small on the scales used. This honest representation of effect magnitude is important context for researchers evaluating the compound’s evidence tier.
The FDA Approval of Bremelanotide (Vyleesi): Regulatory Record
As documented regulatory fact: the U.S. FDA approved bremelanotide, marketed as Vyleesi by AMAG Pharmaceuticals, in June 2019 for a specific indication. The approval was based on the RECONNECT Phase 3 data and the complete clinical development program. This makes bremelanotide one of a small number of peptide-class compounds with a formally approved pharmaceutical application, placing it in a distinct regulatory category from compounds like BPC-157 or Ipamorelin, which have no approved human therapeutic use in any jurisdiction. The Dhillon and Keam (2019) Drugs approval review, indexed at PMID 31429064, documents the regulatory milestones through FDA approval.
Critical distinction for researchers: The FDA approval applies specifically to the pharmaceutical product Vyleesi (bremelanotide 1.75 mg subcutaneous injection, manufactured under pharmaceutical GMP) for the approved indication, in the approved patient population, under medical supervision. Research-grade PT-141 purchased through research supply channels is not the same as Vyleesi, has not undergone pharmaceutical manufacturing controls, and is classified as an unapproved research compound for non-human use. The existence of an FDA-approved pharmaceutical analogue does not alter the research-use classification of non-pharmaceutical-grade material.
Evidence Tier: An Honest Assessment
Bremelanotide/PT-141 occupies an unusual position in the research peptide landscape, it is the only compound in the common research peptide set with a direct pharmaceutical equivalent that has completed Phase 3 trials and received FDA approval. This affects how its evidence tier should be read:
| Evidence Level | Status for Bremelanotide/PT-141 (as of 2026) |
|---|---|
| Human Phase 3 randomized controlled trials | Completed, RECONNECT Studies 301 and 302; 1, 247 subjects; both met co-primary endpoints |
| Phase 2 controlled trials | Completed, multiple Phase 2 studies including intranasal formulation; documented in development record |
| Receptor pharmacology characterization | Documented, MC3R/MC4R agonist; CNS-mediated pathway; GPCR mechanism established |
| FDA approval status (pharmaceutical form) | Approved (Vyleesi, 2019) for specific indication in premenopausal subjects |
| Research-grade PT-141 approval status | Not approved for human use, research compound classification applies |
| WADA status | Prohibited, Section S0 (Non-Approved Substances) for non-prescription use |
The limitation to state plainly: The Phase 3 RECONNECT trial effect sizes, while statistically significant, were numerically modest on the validated scales used. The Mayer and Lynch (2020) systematic review noted that “the clinical benefit may only be modest.” Statistically significant group differences in controlled trials do not translate automatically to large individual-level effects. Researchers should read the primary trial publications, not summaries, to accurately understand the magnitude of documented outcomes.
Regulatory and WADA Status
FDA (United States)
The FDA-approved pharmaceutical bremelanotide (Vyleesi) is a prescription drug available through licensed healthcare providers for the approved indication. Research-grade PT-141 sourced outside the pharmaceutical supply chain is not FDA approved for any human therapeutic use. The FDA evaluates products, not compounds in isolation; the existence of an approved pharmaceutical form does not grant approval to non-pharmaceutical-grade material. Researchers should consult current FDA guidance and their institutional review protocols directly.
WADA (World Anti-Doping Agency)
WADA classifies bremelanotide/PT-141 under Section S0: Non-Approved Substances when used outside the context of a lawful medical prescription. S0 covers any pharmacological substance used in a manner not consistent with an authorized regulatory approval. Athletes subject to WADA rules, even those with a legitimate medical prescription, should consult their national anti-doping authority regarding Therapeutic Use Exemption (TUE) requirements before any use. The prohibition applies both in-competition and out-of-competition.
Relationship to the Melanocortin System and Related Compounds
Bremelanotide’s receptor targets, MC3R and MC4R, are part of a five-receptor family (MC1R through MC5R) that evolved as mediators of diverse physiological functions downstream of POMC cleavage products, including adrenocorticotropic hormone (ACTH), α-MSH, β-MSH, and γ-MSH. The Bardhan et al. (2025) review in Diseases documents that MC4R is also implicated in monogenic obesity, energy homeostasis, and inflammatory regulation in preclinical models, illustrating that bremelanotide’s studied indication represents only one research application of a pharmacologically rich receptor class.
Researchers situating bremelanotide within a broader hormonal research context may also find value in reviewing the Kisspeptin profile, a neuropeptide that operates within the GnRH-LH-FSH reproductive axis, providing a distinct but related CNS-hormonal research reference point, and the hormonal peptide cluster overview in the Research Journal. For methodology on evaluating the evidence quality of any compound profile, see How to Read an Evidence Tier.
Frequently Asked Questions About PT-141 (Bremelanotide)
What is PT-141 (bremelanotide) and how does it differ from Melanotan II?
PT-141 (bremelanotide) is a synthetic cyclic heptapeptide analogue of α-MSH and a direct metabolite of Melanotan II. The structural difference, loss of the C-terminal amide, eliminates Melanotan II’s melanogenic (tanning) activity while preserving MC3R and MC4R binding. Bremelanotide is the active pharmaceutical form developed through Palatin Technologies’ clinical program and received FDA approval in 2019 as Vyleesi. Melanotan II and research-grade PT-141 distributed outside the pharmaceutical supply chain are distinct, unapproved research compounds.
What did the RECONNECT Phase 3 trials of bremelanotide find?
The two RECONNECT trials (Kingsberg et al., 2019) enrolled 1, 247 subjects in randomized, double-blind, placebo-controlled 24-week studies. Both met co-primary efficacy endpoints: statistically significant improvements in the Female Sexual Function Index desire domain and Female Sexual Distress Scale Item 13. Effect sizes were modest in absolute terms. Treatment-emergent adverse events, nausea (≈40%), flushing (≈20%), headache (≈11%), occurred substantially more often in the active arm than placebo. These are the primary human efficacy data on record for this compound class.
Is bremelanotide (Vyleesi) FDA approved?
Yes, as a pharmaceutical drug for a specific indication. The FDA approved Vyleesi (bremelanotide) in June 2019 based on the RECONNECT Phase 3 trial data. This approval applies to the pharmaceutical product manufactured under GMP controls, dispensed by prescription for the approved indication. Research-grade PT-141 available through research supply channels is not the same product, is not FDA approved for human use, and carries full research-compound classification regardless of the pharmaceutical approval of its analogue.
Where is PT-141/bremelanotide on the WADA Prohibited List?
WADA classifies bremelanotide under Section S0: Non-Approved Substances for use outside an authorized medical prescription. The S0 category covers any pharmacological substance whose use is inconsistent with an applicable regulatory authorization. Athletes subject to WADA rules should consult the current Prohibited List and their anti-doping authority regarding Therapeutic Use Exemption procedures before any use.
For educational and research reference purposes only. Not medical advice. Not for human use. PT-141 (bremelanotide) in research-grade form is not approved by the FDA for human use. This article documents published scientific literature and regulatory records for educational and reference purposes only; nothing here is intended to diagnose, treat, cure, or prevent any disease, or to recommend human use of any compound. The FDA approval of the pharmaceutical product Vyleesi applies specifically to that licensed pharmaceutical under medical supervision, it does not apply to research-grade material. All citations link to primary sources, read them in full. Must be 21+.