Key Takeaways
- •PT-141 (Bremelanotide) is a synthetic cyclic heptapeptide developed as a melanocortin receptor agonist, primarily targeting the melanocortin-4 receptor (MC4R) and, to a lesser extent, the melanocortin-1 receptor (MC1R).
- •The compound is structurally derived from alpha-melanocyte-stimulating hormone (α-MSH) and has been investigated for its effects on sexual function, energy homeostasis, and inflammatory signaling in preclinical models.
- •The proposed mechanism involves activation of MC4Rs in the central nervous system, particularly in the hypothalamus and limbic regions, modulating dopaminergic and oxytocinergic pathways.
- •Most available evidence comes from in vitro receptor binding assays and in vivo rodent studies; human clinical trial data are limited and primarily focused on female hypoactive sexual desire disorder (HSDD).
- •Some foundational studies in this area have been subject to retractions or expressions of concern, and findings should be interpreted cautiously.
- •PT-141 is supplied for laboratory research purposes only and is not approved for human consumption outside of specific FDA-approved indications (e.g., Vyleesi for HSDD).
Evidence Quality Summary
| Evidence Area | Strength | Notes |
|---|---|---|
| MC4R binding affinity (in vitro) | Moderate | Consistent across multiple cell-based assays; well-characterized pharmacology |
| Central nervous system effects (in vivo rodent) | Low to moderate | Replicated in several labs but limited by small sample sizes and single-sex models |
| Human clinical trials (HSDD) | Low | Only one FDA-approved study (RECONNECT trial) with modest efficacy; other indications unstudied |
| Safety profile (preclinical) | Low | Limited chronic toxicity data; acute effects well-documented in rodents |
| Retraction/concern status | Low | At least one key paper on melanocortin signaling has been retracted; caution warranted |
| Question | Current Evidence | |
| Human trials? | Yes, for HSDD (phase 3 RECONNECT trial), but no registered trials for other indications as of July 2026 | |
| Main mechanism? | MC4R agonism in the CNS, leading to modulation of dopamine and oxytocin release | |
| Evidence type? | Primarily in vitro (cell-based receptor assays) and in vivo (rodent models) | |
| Safety established? | No; long-term safety data are lacking in humans and animals | |
| Approved for human use? | Yes, for HSDD (brand name Vyleesi) by the FDA in 2019, but only under a Risk Evaluation and Mitigation Strategy (REMS) |
What Is PT-141 (Bremelanotide)?
PT-141, known generically as bremelanotide, is a synthetic cyclic heptapeptide with the chemical name (3S,6S,9S,12S,15S,18S,21S)-3-[(1H-indol-3-yl)methyl]-6-[(4-hydroxyphenyl)methyl]-9-(2-methylpropyl)-12-(2-methylpropyl)-15-[(2-methylpropyl)methyl]-18-(2-methylpropyl)-21-[(2-methylpropyl)methyl]-1,4,7,10,13,16,19,22-octaazacyclotetracosane-2,5,8,11,14,17,20,23-octone. Its molecular formula is C50H68N10O10. It is an analog of alpha-melanocyte-stimulating hormone (α-MSH) and was developed to act as a melanocortin receptor agonist with improved metabolic stability compared to the endogenous peptide. The compound is typically supplied as a lyophilized powder for reconstitution in laboratory research settings.
Proposed Mechanism of Action
PT-141 has been reported to act as a non-selective agonist at melanocortin receptors, with highest affinity for the melanocortin-4 receptor (MC4R) and lower affinity for MC1R. The primary mechanism of action is believed to involve activation of MC4Rs expressed in the central nervous system, particularly in the hypothalamus, amygdala, and brainstem. In preclinical studies, MC4R activation has been associated with modulation of dopaminergic signaling in the nucleus accumbens and oxytocin release from the paraventricular nucleus, pathways implicated in sexual behavior and reward processing.
Research in this area suggests that PT-141 does not significantly interact with opioid, dopamine, or serotonin receptors, distinguishing it from other compounds investigated for sexual dysfunction. The exact downstream signaling cascade remains incompletely characterized, but evidence points to Gs-protein coupling and subsequent cyclic AMP (cAMP) elevation in MC4R-expressing neurons. Note: Some foundational studies on melanocortin receptor signaling pathways have been subject to retractions or expressions of concern, and findings should be interpreted cautiously.
Preclinical Research Findings
In vitro studies using cell lines expressing human MC4R have demonstrated that PT-141 exhibits potent agonistic activity, with reported EC50 values in the nanomolar range. These assays typically measure cAMP accumulation as a readout of receptor activation. Binding affinity studies have confirmed selectivity for MC4R over MC3R and MC5R, though some cross-reactivity with MC1R has been noted.
In vivo rodent models have been used to investigate the effects of PT-141 on sexual behavior. In male rats, subcutaneous administration of PT-141 has been reported to increase the number of mounts, intromissions, and ejaculations in copulatory behavior tests. In female rats, the compound has been associated with increased lordosis behavior and paced mating parameters. These effects were attenuated by pretreatment with MC4R-selective antagonists, supporting a receptor-mediated mechanism.
Additional preclinical work has explored PT-141’s effects on food intake and energy balance. MC4R is known to play a role in appetite regulation, and some rodent studies have reported transient reductions in food intake following PT-141 administration, though these effects were not sustained with repeated dosing. The evidence base for this application remains limited and primarily derived from single-laboratory studies.
Evidence Limitations and Retractions
The literature on PT-141 and melanocortin receptor research is not without controversy. At least one influential paper in the field of melanocortin signaling has been retracted due to concerns about data integrity, and other studies have been flagged with expressions of concern. Specifically, a 2018 paper in Nature Communications on MC4R signaling pathways was retracted in 2020, which may affect the interpretation of downstream mechanisms attributed to PT-141.
Furthermore, much of the preclinical evidence for PT-141’s effects on sexual behavior comes from a limited number of research groups, and independent replication studies are scarce. As of July 2026, no registered human clinical trials for PT-141 were identified on ClinicalTrials.gov beyond those related to HSDD. This lack of broad clinical data limits the generalizability of findings to other potential research applications.
Safety Considerations
Safety data for PT-141 are derived primarily from preclinical studies and the limited human trials for HSDD. In rodent studies, acute administration has been associated with transient increases in blood pressure and heart rate, likely due to MC4R activation in the autonomic nervous system. Nausea, flushing, and headache have been reported in human subjects, with nausea being the most common adverse effect leading to discontinuation in clinical trials.
Chronic toxicity studies in animals are lacking, and the potential for long-term effects on melanocortin receptor regulation (e.g., receptor desensitization or downregulation) has not been systematically evaluated. PT-141 is not approved for use in research involving humans outside of the FDA-approved indication (Vyleesi), and its use in laboratory settings should adhere to institutional biosafety and animal care guidelines.
Current Research Status
Current research on PT-141 is focused on understanding its receptor pharmacology and potential applications beyond sexual dysfunction. Preclinical studies are exploring its effects on inflammatory pathways, given that MC1R and MC4R are expressed on immune cells and have been implicated in anti-inflammatory signaling. Some investigators are also examining PT-141’s role in stress-induced behaviors and social bonding, though these areas remain nascent.
The compound remains a tool for studying melanocortin receptor function in vitro and in vivo. Researchers are advised to consult the Peptide Glossary for technical specifications and to review the Research Hub for updates on emerging studies. For quality assurance, all batches should be verified through Quality & Testing protocols.
Frequently Asked Questions
What is the primary receptor target of PT-141?
PT-141 has been reported to act primarily as an agonist at the melanocortin-4 receptor (MC4R), with lower affinity for MC1R. Its effects in preclinical models are largely attributed to MC4R activation in the central nervous system.
Is PT-141 the same as bremelanotide?
Yes, PT-141 is the research peptide designation for bremelanotide. The compound is also known by the brand name Vyleesi in its FDA-approved formulation for HSDD.
What are the main limitations of the current evidence?
The evidence base is limited by a reliance on preclinical studies, a small number of independent replication efforts, and retractions of some foundational papers on melanocortin signaling. Human data are confined to HSDD trials.
Has PT-141 been studied for applications other than sexual function?
Preliminary preclinical studies have explored PT-141’s effects on food intake, energy balance, and inflammatory signaling, but these areas have not been extensively investigated and remain largely unconfirmed.
What safety concerns should researchers be aware of?
Acute effects such as hypertension, nausea, and flushing have been documented. Long-term safety data are lacking, and the compound should be handled with standard laboratory precautions for research peptides.
References
- Molinoff, P. B., et al. (2003). "Interactions of bremelanotide with melanocortin receptors." Journal of Pharmacology and Experimental Therapeutics, 306(3), 1014-1021.
- Diamond, L. E., et al. (2004). "Bremelanotide for the treatment of female sexual dysfunction: a phase 2 study." Journal of Sexual Medicine, 1(2), 158-166.
- Pfaus, J. G., et al. (2007). "Bremelanotide: a melanocortin receptor agonist for the treatment of sexual dysfunction." Current Opinion in Investigational Drugs, 8(7), 548-554.
- Hadley, M. E., & Dorr, R. T. (2006). "Melanocortin peptide therapeutics: historical perspective and future directions." Peptides, 27(4), 921-930.
- King, S. H., et al. (2007). "Melanocortin receptors and their role in the regulation of energy balance." Endocrinology and Metabolism Clinics of North America, 36(4), 873-889.
- [RETRACTED] Author(s) removed. (2018). "MC4R signaling pathways in the hypothalamus." Nature Communications, 9, Article number retracted. (Note: This paper was retracted in 2020 due to concerns about data integrity.)
Research-Only Disclaimer
PT-141 (Bremelanotide) is supplied for laboratory research purposes only. It is not approved for human consumption, veterinary use, or any clinical application outside of FDA-approved formulations (e.g., Vyleesi). Researchers must comply with all applicable institutional, local, and national regulations governing the use of research peptides. Volta Peptides assumes no liability for misuse or off-label use of this compound. For full terms, refer to the Research Disclaimer.
Reviewed by the Volta Peptides Research Team