PT-141, also known by its chemical name bremelanotide, is a synthetic cyclic heptapeptide that acts as an agonist at melanocortin receptors, a small family of G protein-coupled receptors that includes MC1R, MC3R and MC4R. It was characterized in the pharmacology literature as the deamidated metabolite of melanotan-2, sharing the same cyclic peptide backbone but differing at one terminus. In research contexts, PT-141 is supplied as a lyophilized reference compound for in vitro and laboratory study of melanocortin receptor pharmacology, not as a product for human or animal use.
| Attribute | Detail |
|---|---|
| Name | PT-141 (bremelanotide) |
| Class | Melanocortin receptor agonist, cyclic heptapeptide |
| Structure | Seven-residue cyclic peptide, reported as the carboxylic-acid (deamidated) form of melanotan-2 |
| Origin | Synthetic analog derived from alpha-MSH research, isolated as the active metabolite of melanotan-2 |
| Receptors studied | MC1R, MC3R, MC4R (MC3R and MC4R are expressed primarily in the central nervous system) |
| Related approved drug | Vyleesi (bremelanotide injection), FDA-approved prescription medicine, NDA 210557 |
| What studies examine | Receptor binding and selectivity, CNS neuronal activation in rodent models, cardiovascular parameters, approved-drug clinical trial data |
| Form supplied (research) | Lyophilized powder, research use only, not for human or animal use |
What Is PT-141 (Bremelanotide)?
PT-141 is the research and development code name for bremelanotide, a peptide originally investigated by Palatin Technologies as part of a melanocortin receptor research program (Molinoff et al., 2003). In the pharmacology literature, PT-141 is described as a synthetic peptide analog of alpha-melanocyte-stimulating hormone (alpha-MSH) that functions as an agonist at melanocortin receptors (Molinoff et al., 2003). The molecule shares its cyclic, lactam-bridged heptapeptide scaffold with melanotan-2, a related research compound covered in the site's PT-141 research library monograph.
As a chemical entity, bremelanotide is understood in the literature as the deamidated form of melanotan-2: where melanotan-2 carries a terminal amide group, bremelanotide carries a free carboxylic acid at the corresponding position. That single change in the C-terminal chemistry is the structural distinction researchers point to when explaining why the two peptides are studied and reported as related but distinct compounds. For a side-by-side comparison of the two, see the PT-141 vs melanotan-2 research library entry and the melanotan-1 vs melanotan-2 article.
How Does PT-141 Act on Melanocortin Receptors?
The melanocortin receptor family consists of five subtypes, MC1R through MC5R, which are class A G protein-coupled receptors with distinct tissue distributions (see the melanocortin receptor ligand review cited below). MC1R is best known for its role in melanocyte pigmentation research. MC3R and MC4R, by contrast, are expressed primarily in the central nervous system and are described in the literature as the "neural" melanocortin receptors, with roles studied in hypothalamic circuits that govern energy balance and other centrally mediated processes (Yuan and Tao, 2022; Girardet and Butler, 2014).
According to the FDA-approved prescribing information for bremelanotide, the compound nonselectively activates multiple melanocortin receptor subtypes, with a reported order of potency of MC1R, MC4R, MC3R, MC5R and MC2R, and binding at MC1R and MC4R identified as most relevant at therapeutic dose levels of the approved drug. In a rat model, systemic administration of PT-141 was reported to activate neurons in the hypothalamus, measured by an increase in c-Fos immunoreactivity, a standard marker of neuronal activation used in this line of research (Molinoff et al., 2003). The same report noted that neurons in this hypothalamic region take up pseudorabies virus injected into rat tissue connected to the same neural circuit, which the authors used to map the pathway under study.
Is PT-141 the Same as the Prescription Drug Vyleesi?
No. Bremelanotide is the active ingredient in Vyleesi (bremelanotide injection), a prescription medicine that received FDA approval in 2019 for a specific indication in a defined patient population, administered as a single-dose autoinjector under a physician's supervision (FDA approval letter, NDA 210557; FDA prescribing information). Vyleesi is an approved drug product manufactured, tested and labeled to FDA drug standards, with its own dosing, contraindications and monitoring requirements set out in its FDA label.
The bremelanotide sold by Homegrown Peptides as PT-141 is a research-grade peptide intended solely for laboratory and in vitro research use. It is not Vyleesi, it is not manufactured or reviewed as a drug product, and it is not for human or animal use. Any clinical facts referenced in this article regarding the approved medicine are attributed to the FDA-approved labeling and application materials for Vyleesi, not to the research material described here.
What Have Preclinical and Clinical Studies Examined?
Rodent and nonhuman primate research
Early pharmacology work summarized by Molinoff et al. (2003) reported that administration of PT-141 to rats and nonhuman primates was studied in models of penile erection, alongside the hypothalamic c-Fos and pseudorabies-tracing experiments described above. The authors framed these findings as evidence for a specific central nervous system pathway linking melanocortin receptor activation in the hypothalamus to genital neural circuits in the animal models used.
Human clinical trials of the approved drug
A double-blind, placebo-controlled trial evaluated the safety, pharmacokinetic properties and pharmacodynamic effects of intranasal PT-141 in healthy male volunteers and in patients with mild-to-moderate erectile dysfunction (Diamond et al., 2004). This trial was conducted during the drug-development phase that preceded the eventual approval of a different (subcutaneous) formulation and a different indication (Vyleesi, for hypoactive sexual desire disorder in premenopausal women). It is cited here only to describe what was studied and reported in the peer-reviewed literature, not as a description of any current research-grade product use.
Cardiovascular findings from the pivotal ambulatory blood pressure trial
A randomized, double-blind, placebo-controlled, parallel-arm trial in 397 premenopausal women examined the effect of three bremelanotide doses on ambulatory blood pressure and heart rate over 24-hour monitoring periods (White et al., 2017, Journal of Hypertension). The trial reported small, transient increases in ambulatory systolic and diastolic blood pressure relative to placebo following dosing, with peak increases typically lasting under 15 minutes, accompanied by corresponding reductions in heart rate during the same interval. These findings were reported specifically for the FDA-reviewed drug development program and are summarized here as an example of the cardiovascular pharmacology literature associated with MC4R agonism, not as a safety profile for any research-only material.
How Does PT-141 Differ From Melanotan-2?
PT-141 and melanotan-2 are frequently discussed together because they share a common synthetic origin and the same cyclic heptapeptide core. The distinctions researchers draw between them center on the C-terminal chemistry described above (amide in melanotan-2, carboxylic acid in bremelanotide) and on which melanocortin receptor subtypes each is reported to engage most strongly in the published literature, with melanotan-2 more closely associated with MC1R-mediated pigmentation research and bremelanotide more closely associated with MC3R/MC4R-focused central nervous system research. A full structural and receptor-binding comparison, including citations specific to each compound, is maintained in the PT-141 vs melanotan-2 research library entry, and background on melanotan-2 itself and its own comparator, melanotan-1, is available in the melanotan-1 vs melanotan-2 article.
Handling Notes for the Research Bench
PT-141 is supplied to laboratories as a lyophilized (freeze-dried) powder that requires reconstitution with an appropriate diluent before use in an assay, and like other lyophilized research peptides it should be stored per the certificate of analysis and protected from unnecessary freeze-thaw cycles and light exposure between uses. The math for calculating a working concentration from a lyophilized vial, and the choice of diluent, is covered step by step in this site's peptide reconstitution guide; bacteriostatic water is one of the diluents commonly referenced for bench-scale reconstitution of lyophilized research peptides. As with any research peptide, the certificate of analysis for a given lot, not a general product description, is the reference for verifying identity and purity on our PT-141 lot page before it is used in an experiment.
Frequently asked questions
Is PT-141 the same molecule as bremelanotide?
Yes. PT-141 is the development code name used in the early pharmacology literature for the peptide now known by its chemical name, bremelanotide, which is also the active ingredient in the FDA-approved drug Vyleesi. The research-grade PT-141 sold for laboratory use is not Vyleesi and is not for human or animal use.
What receptors does PT-141 target?
Published pharmacology data describe PT-141 as a nonselective agonist across the melanocortin receptor family, with FDA labeling for the approved drug reporting an order of potency of MC1R, MC4R, MC3R, MC5R and MC2R, and MC1R and MC4R identified as most relevant at therapeutic exposure of the approved medicine. MC3R and MC4R are the subtypes expressed primarily in the central nervous system.
Is PT-141 derived from melanotan-2?
The pharmacology literature describes bremelanotide as the deamidated metabolite of melanotan-2, meaning the two peptides share the same cyclic backbone but differ at the C-terminus, where melanotan-2 has an amide and bremelanotide has a carboxylic acid.
Is the PT-141 sold by Homegrown Peptides the same as the drug Vyleesi?
No. Vyleesi is an FDA-approved prescription medicine manufactured, tested and labeled to drug standards for a specific approved indication. The bremelanotide sold here is a research-grade peptide intended solely for laboratory and in vitro research and is not manufactured, reviewed or labeled as a drug. It is not for human or animal use.
What have clinical trials of bremelanotide reported?
Trials conducted for the approved drug program have examined pharmacokinetics, receptor pharmacology and cardiovascular parameters such as ambulatory blood pressure and heart rate, reporting small and transient blood-pressure increases following dosing in the reviewed trial population. These findings are specific to the approved drug's clinical development program and its reviewed population, and are described here only as a summary of the published literature.
How is research-grade PT-141 supplied?
It is supplied as a lyophilized powder for laboratory research use, intended to be reconstituted at the bench for use in research applications such as receptor-binding or cell-based assays. It is Research Use Only and not for human or animal consumption.
References
- U.S. Food and Drug Administration. NDA 210557 Approval Letter, Vyleesi (bremelanotide injection). accessdata.fda.gov/drugsatfda_docs/appletter/2019/210557Orig1s000ltr.pdf
- U.S. Food and Drug Administration. Highlights of Prescribing Information, VYLEESI (bremelanotide injection). accessdata.fda.gov/drugsatfda_docs/label/2020/210557s002lbl.pdf
- Molinoff PB, Shadiack AM, Earle D, Diamond LE, Quon CY. PT-141: a melanocortin agonist for the treatment of sexual dysfunction. Ann N Y Acad Sci. 2003. pubmed.ncbi.nlm.nih.gov/12851303
- Diamond LE, Earle DC, Rosen RC, Willett MS, Molinoff PB. Double-blind, placebo-controlled evaluation of the safety, pharmacokinetic properties and pharmacodynamic effects of intranasal PT-141 in healthy males and patients with mild-to-moderate erectile dysfunction. Int J Impot Res. 2004. pubmed.ncbi.nlm.nih.gov/14963471
- White WB, Myers MG, Jordan R, Lucas J. Usefulness of ambulatory blood pressure monitoring to assess the melanocortin receptor agonist bremelanotide. J Hypertens. 2017. pmc.ncbi.nlm.nih.gov/articles/PMC5338879
- Yuan XC, Tao YX. Ligands for Melanocortin Receptors: Beyond Melanocyte-Stimulating Hormones and Adrenocorticotropin. 2022. pmc.ncbi.nlm.nih.gov/articles/PMC9599618
- Girardet C, Butler AA. Neural melanocortin receptors in obesity and related metabolic disorders. 2014. pmc.ncbi.nlm.nih.gov/articles/PMC3819409
- UniProt Consortium. MC4R_HUMAN, Melanocortin receptor 4 (P32245). uniprot.org/uniprotkb/P32245/entry
Research use only. Homegrown Peptides products are for laboratory research and are not for human or animal use. Nothing in this article is medical advice.
