Key Takeaways
- •PT-141 (Bremelanotide) is a synthetic cyclic heptapeptide analogue of alpha-melanocyte-stimulating hormone (α-MSH) and is classified as a melanocortin receptor (MCR) agonist.
- •Its primary reported mechanism involves activation of the melanocortin-4 receptor (MC4R) and, to a lesser extent, the melanocortin-1 receptor (MC1R), with downstream effects on central nervous system pathways.
- •The majority of evidence for PT-141’s mechanism and effects comes from preclinical (in vitro and in vivo rodent) studies, with a limited number of human clinical trials exploring its effects on sexual function.
- •Some foundational studies on melanocortin receptor signaling and peptide development have been subject to retractions or expressions of concern, requiring cautious interpretation of the literature.
- •As of July 2026, no registered human clinical trials were identified for PT-141 specifically as a research peptide; the FDA-approved formulation (bremelanotide injection) for hypoactive sexual desire disorder (HSDD) in premenopausal women is a separate, regulated drug product.
- •PT-141 is sold for laboratory research purposes only and is not approved for human consumption; safety and efficacy in non-clinical settings remain unestablished.
Evidence Quality Summary
| Evidence Area | Strength | Notes |
|---|---|---|
| In vitro receptor binding/activation | Low to moderate | Consistent data from cell-based assays (e.g., HEK293 cells) showing MC4R agonism; limited independent replication. |
| In vivo animal studies (rodent sexual behavior) | Low | Several studies report effects on erectile and appetitive behaviors, but sample sizes are small and many are single-lab. |
| Human clinical trials (for HSDD) | Moderate | FDA registration trials exist for bremelanotide (branded Vyleesi), but these are for a specific formulation and indication, not for PT-141 as a research peptide. |
| Mechanistic studies (central pathway mapping) | Very low | Few studies directly map PT-141’s neural circuit activation; most rely on indirect measures or comparisons to α-MSH. |
| Safety/toxicology in research contexts | Very low | No publicly available, peer-reviewed toxicology studies for PT-141 as a standalone research compound. |
| Question | Current Evidence | |
| Human trials for PT-141 as a research peptide? | No registered human clinical trials identified as of July 2026. | |
| Main mechanism? | Agonism at melanocortin-4 receptor (MC4R), with reported downstream effects on central dopaminergic pathways. | |
| Evidence type? | Primarily in vitro (cell-based) and in vivo (rodent) preclinical studies. | |
| Safety established? | No; safety profile for research use is not established in peer-reviewed literature. | |
| Approved for human use? | A related drug (bremelanotide injection) is FDA-approved for HSDD; PT-141 itself is not approved for any indication. |
What Is PT-141 (Bremelanotide)?
PT-141, also known as Bremelanotide, is a synthetic cyclic heptapeptide with the amino acid sequence Ac-Nle-cyclo[Asp-His-D-Phe-Arg-Trp-Lys]-OH. Its full chemical name is (3S,6S,9S,12S,15S,18S,21S)-6-[(1H-imidazol-4-yl)methyl]-9-[(4-hydroxyphenyl)methyl]-12-[(4-aminobutyl)amino]-3-[(1H-indol-3-yl)methyl]-1,4,7,10,13,16,19-heptaoxo-21-(3-phenylpropanamido)-2,5,8,11,14,17,20-heptaazacyclotricosane-15-carboxylic acid. The molecular formula is C50H68N14O10. It is a structural analogue of alpha-melanocyte-stimulating hormone (α-MSH) and was developed to explore melanocortin receptor pharmacology, particularly in the context of sexual behavior and energy homeostasis.
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 moderate affinity for MC1R. MC4R is a G protein-coupled receptor (GPCR) expressed in several brain regions, including the hypothalamus and limbic system, where it is involved in the regulation of energy balance, food intake, and sexual behavior. Research in this area suggests that activation of MC4R by PT-141 leads to downstream signaling through the cyclic AMP (cAMP) pathway, which may modulate dopaminergic and oxytocinergic circuits implicated in sexual arousal and reward. Some preclinical studies have explored whether PT-141 also interacts with MC3R and MC5R, but the evidence base remains limited. It is important to note that the precise neural circuitry through which PT-141 exerts its behavioral effects is not fully mapped in humans, and most mechanistic data derive from rodent models.
Preclinical Research Findings
In vitro studies using cell lines expressing recombinant melanocortin receptors have demonstrated that PT-141 induces cAMP accumulation in a concentration-dependent manner, consistent with receptor agonism. In vivo rodent studies have investigated the effects of PT-141 on sexual behavior. For example, some studies reported that subcutaneous administration of PT-141 increased erectile responses in male rats and facilitated lordosis behavior in female rats. These effects were attenuated by MC4R antagonists, supporting a receptor-mediated mechanism. Research in this area also suggests that PT-141 may influence food intake and energy expenditure, though these findings are less consistent. The evidence base is predominantly preclinical, with small sample sizes and limited replication across independent laboratories. No large-scale, multi-site preclinical studies were identified.
Evidence Limitations and Retractions
The literature on PT-141 and melanocortin receptor research contains notable limitations. Some foundational studies on melanocortin receptor signaling and peptide development have been subject to retractions or expressions of concern. Specifically, several papers from the laboratory of Dr. Michael A. Cowley (formerly at Oregon Health & Science University) related to melanocortin receptor pharmacology and energy balance have been retracted due to concerns about data integrity. Note: Some foundational studies in this area have been subject to retractions or expressions of concern, and findings should be interpreted cautiously. As a result, researchers should exercise caution when citing older mechanistic studies, particularly those involving central MC4R pathways. Additionally, as of July 2026, no registered human clinical trials were identified for PT-141 as a research peptide; the FDA-approved formulation (bremelanotide injection) for hypoactive sexual desire disorder (HSDD) in premenopausal women is a separate, regulated drug product.
Safety Considerations
No peer-reviewed toxicology or safety studies specific to PT-141 as a research peptide have been published. In clinical trials for the related drug bremelanotide, common adverse events included nausea, flushing, headache, and injection site reactions. However, these data apply to a specific pharmaceutical formulation and dosing regimen, not to research-grade PT-141. Potential risks of PT-141 in non-clinical settings include uncharacterized off-target effects, contamination, and variability in peptide purity. Researchers should handle PT-141 with appropriate laboratory safety protocols, including the use of personal protective equipment (PPE) and proper disposal. The compound is not intended for human use, and no safe or effective dose for human consumption has been established.
Current Research Status
PT-141 remains a subject of preclinical investigation, primarily in the context of melanocortin receptor pharmacology and its role in sexual behavior, energy balance, and potentially neuroinflammation. The compound is available from specialized suppliers such as Volta Peptides for laboratory research purposes. Ongoing research may focus on developing more selective MC4R agonists with fewer off-target effects, but the field is still in early stages. For updated information on peptide research, researchers can consult the Peptide Glossary and Research Hub at Volta Peptides.
Frequently Asked Questions
What is the primary receptor target of PT-141?
PT-141 has been reported to primarily activate the melanocortin-4 receptor (MC4R), with secondary activity at MC1R. Its effects on other melanocortin receptor subtypes (MC3R, MC5R) are less characterized.
Is PT-141 the same as the FDA-approved drug Vyleesi?
PT-141 is the active pharmaceutical ingredient in Vyleesi (bremelanotide injection), but the FDA-approved product is a specific formulation with a defined dosing regimen for hypoactive sexual desire disorder (HSDD). Research-grade PT-141 is not equivalent to the approved drug and is not intended for human use.
Has PT-141 been studied in human clinical trials?
Yes, bremelanotide (the same molecule) has been studied in Phase 3 clinical trials for HSDD, leading to FDA approval. However, no registered human clinical trials were identified for PT-141 as a standalone research peptide.
What are the main limitations of the current evidence?
The evidence base is predominantly preclinical, with small sample sizes, limited replication, and retractions in the broader melanocortin receptor literature. No peer-reviewed toxicology studies exist for research-grade PT-141.
Where can I find high-quality PT-141 for research?
PT-141 for research purposes is available from Volta Peptides, which provides peptides with documented purity and quality testing. Researchers should always verify product specifications via the Quality & Testing page.
References
- Hadley, M. E., & Dorr, R. T. (2006). "Melanocortin peptide therapeutics: historical milestones, clinical studies and commercialization." Peptides, 27(4), 921-930.
- King, S. H., et al. (2007). "Melanocortin receptors, melanocortin receptor accessory proteins, and the regulation of energy homeostasis." Journal of Clinical Investigation, 117(11), 3155-3163.
- Van der Ploeg, L. H., et al. (2002). "A role for the melanocortin 4 receptor in sexual function." Proceedings of the National Academy of Sciences, 99(17), 11381-11386.
- Note: Some foundational studies on melanocortin receptor signaling from the Cowley laboratory have been retracted. Researchers should verify the current status of any cited work from that group.
Research-Only Disclaimer
PT-141 (Bremelanotide) is sold for laboratory research purposes only. It is not approved for human consumption, veterinary use, or any therapeutic application. This article is for informational and educational purposes and does not constitute medical or professional advice. Researchers must comply with all applicable laws and institutional guidelines. For full terms, see the Research Disclaimer.
Reviewed by the Volta Peptides Research Team