What Is PT-141 (Bremelanotide)?
PT-141, known by its International Nonproprietary Name bremelanotide, is a synthetic cyclic heptapeptide that acts as an agonist at melanocortin receptors. It is one of the few compounds in the research peptide category that has completed a full pharmaceutical development programme: a subcutaneous formulation was approved by the US Food and Drug Administration in 2019 under the brand name Vyleesi. In Australia it is not entered on the Australian Register of Therapeutic Goods (ARTG), and research-grade PT-141 is supplied for laboratory use only.
Searches for "PT-141 Australia" and "PT141 Australia" have grown steadily, largely because the compound sits at an unusual intersection of research fields: melanocortin pharmacology, hypothalamic signalling, and the history of the melanotan programme. This guide explains where PT-141 came from, how it engages the melanocortin system, what the published clinical literature reports, and how the compound is handled in a research setting. Optic Labs supplies research-grade PT-141 10mg in Australia, third-party HPLC tested, with a Certificate of Analysis for each batch.
Where PT-141 Came From: The Melanotan Connection
PT-141's origin story begins at the University of Arizona in the 1980s and 1990s, where researchers were developing analogues of alpha-melanocyte-stimulating hormone (alpha-MSH) to study skin pigmentation. That work produced Melanotan I (afamelanotide) and Melanotan II, a smaller cyclic analogue with broad activity across the melanocortin receptor family. During early studies of Melanotan II, investigators reported effects that had nothing to do with pigmentation and appeared to originate in the central nervous system.
Those observations led to the development of bremelanotide, which is closely related to Melanotan II in structure. The key difference is at the C-terminus: bremelanotide carries a free carboxylic acid where Melanotan II carries an amide. That small change shifts the compound's profile, and development of bremelanotide was taken forward by Palatin Technologies as a centrally acting melanocortin agonist rather than a pigmentation agent. Researchers comparing the two compounds can find our Melanotan 2 10mg listing alongside PT-141 for side-by-side receptor work.
Chemical profile at a glance
- Name: Bremelanotide (PT-141)
- Class: Cyclic heptapeptide, melanocortin receptor agonist
- Sequence: Ac-Nle-cyclo[Asp-His-D-Phe-Arg-Trp-Lys]-OH
- Molecular weight: approximately 1,025 g/mol
- Form supplied for research: lyophilised (freeze-dried) powder in a sealed vial
Mechanism: How PT-141 Engages the Melanocortin System
The melanocortin system consists of five G-protein-coupled receptors, MC1R to MC5R, activated by peptides derived from pro-opiomelanocortin (POMC). MC1R is best known for its role in skin and hair pigmentation, while MC3R and MC4R are expressed widely in the brain, particularly in the hypothalamus, where they influence energy balance, autonomic function and behaviour.
Bremelanotide is a non-selective agonist with its strongest activity at MC4R and MC3R, and some activity at MC1R. Published pharmacology suggests its central effects are mediated through MC4R in hypothalamic regions such as the medial preoptic area, where receptor activation is associated with downstream changes in dopamine signalling. This central site of action is what distinguishes PT-141 from compounds that act on peripheral vascular pathways, and it is the main reason it remains a useful tool compound for researchers studying melanocortin-driven behaviour.
The MC1R activity also explains a finding reported in clinical trials: a small proportion of participants developed focal skin hyperpigmentation, an effect consistent with the pigmentation pathway that the original melanotan research set out to study.
What the Published Clinical Research Reports
Bremelanotide's clinical development makes it unusual among research peptides, because there is a substantial body of peer-reviewed human trial data to draw on. The pivotal studies were the two RECONNECT phase 3 trials, published by Kingsberg and colleagues in Obstetrics & Gynecology in 2019. These randomised, placebo-controlled trials enrolled premenopausal women diagnosed with hypoactive sexual desire disorder and assessed co-primary endpoints of desire and associated distress over a 24-week core phase.
The trials reported statistically significant improvements over placebo on both co-primary endpoints. They also documented the compound's tolerability profile in detail. The most commonly reported adverse events were nausea, flushing and headache, with nausea being the most frequent. Transient increases in blood pressure after administration were also recorded, which is why the approved product carries cautions around cardiovascular conditions.
An earlier intranasal formulation had been studied before the subcutaneous route was chosen. Development of the intranasal version was discontinued after blood pressure increases were observed, and the programme moved to subcutaneous administration, which produced more consistent absorption in later studies.
Pharmacokinetics reported in the literature
Published pharmacokinetic data for subcutaneous bremelanotide report peak plasma concentrations roughly one hour after administration and an elimination half-life in the region of two to three hours. The peptide is cleared by hydrolysis of its amide bonds rather than by significant liver enzyme metabolism. For researchers designing time-course experiments, this relatively short half-life is a key variable when choosing sampling intervals.
PT-141 Compared With Related Compounds
Because PT-141 shares a lineage with other melanocortin peptides, researchers often want to understand how it differs from them:
- PT-141 vs Melanotan II: both are cyclic alpha-MSH analogues. Melanotan II has broader, stronger MC1R activity and was developed around pigmentation, while bremelanotide was developed specifically as a centrally acting MC4R/MC3R agonist and has the more complete clinical data set.
- PT-141 vs afamelanotide (Melanotan I): afamelanotide is a linear analogue focused on MC1R and pigmentation, studied for photoprotection in specific skin conditions. Its research profile is largely separate from PT-141's.
- PT-141 vs peripherally acting compounds: PDE5 inhibitors act on vascular smooth muscle. PT-141's site of action is central, which is why it is studied as a tool for understanding brain melanocortin signalling rather than vascular pharmacology.
Researchers working across several receptor systems may also be interested in our guides on Retatrutide, a GLP-1/GIP/glucagon triple agonist, and the broader plain-English explainer on what peptides are.
Handling, Reconstitution and Storage in the Lab
Research-grade PT-141 is supplied as a lyophilised powder. In this form it is relatively stable, and standard practice is to keep sealed vials cool, dry and away from light, with longer-term storage in a freezer at around -20°C. Once reconstituted, a peptide solution is much more vulnerable to degradation, so reconstituted vials are normally refrigerated at 2–8°C and used within the period set out in the lab's own protocol.
Reconstitution for research typically uses bacteriostatic water, which contains 0.9% benzyl alcohol to limit microbial growth across repeated vial access. To work out concentration from vial size and diluent volume, use our free peptide calculator, and see the reconstitution guide for worked examples of the maths. Our peptide storage guide covers temperature, light and freeze-thaw considerations in more depth.
PT-141 in Australia: Regulation and Sourcing
Bremelanotide is not an approved therapeutic good in Australia and is not listed on the ARTG. Research peptides supplied in Australia cannot be sold or marketed for human therapeutic use, and the scheduling of individual substances under the Poisons Standard can change, so researchers should check the current Standard for the Uniform Scheduling of Medicines and Poisons (SUSMP) before starting work. Our guide to Australian peptide regulation and TGA compliance explains the framework in more detail.
When sourcing PT-141 for research, the most important questions are about identity and purity. A reputable supplier should provide a batch-specific Certificate of Analysis showing HPLC purity and mass spectrometry confirmation that the compound is what the label says. Optic Labs publishes batch results in our COA library, and every vial of PT-141 10mg is third-party tested at 99%+ purity and dispatched from Sydney with Australia-wide shipping.
Frequently Asked Questions
What is PT-141?
PT-141 is the development code for bremelanotide, a synthetic cyclic heptapeptide that activates melanocortin receptors, mainly MC4R and MC3R. It was derived from research on Melanotan II and was approved in the United States in 2019 as Vyleesi. In Australia it is not an approved medicine and is supplied for research use only.
Is PT-141 the same as bremelanotide?
Yes. PT-141 was the compound's code name during development, and bremelanotide is its International Nonproprietary Name. Vyleesi is the US brand name of the approved pharmaceutical product.
How is PT-141 different from Melanotan 2?
The two peptides are structurally very similar, but bremelanotide has a free carboxylic acid at the C-terminus where Melanotan II has an amide. Melanotan II has stronger activity at MC1R, the pigmentation receptor, while PT-141 was developed and clinically studied as a centrally acting MC4R/MC3R agonist.
What side effects were reported in the clinical trials?
In the published phase 3 RECONNECT trials, the most common adverse events were nausea, flushing and headache. Transient blood pressure increases after administration and, less often, focal skin hyperpigmentation were also reported. These findings come from controlled clinical trials of the approved formulation.
Is PT-141 approved in Australia?
No. Bremelanotide is not on the Australian Register of Therapeutic Goods. Research-grade PT-141 sold in Australia is for laboratory and research purposes only and must not be marketed or supplied for human use.
How should PT-141 be stored?
Lyophilised PT-141 is normally stored sealed, cool, dry and away from light, with freezer storage for the long term. After reconstitution with bacteriostatic water, vials are typically kept refrigerated at 2–8°C. See our storage guide for detail.
This article is for educational and research purposes only. Optic Labs products are intended for research use only and are not for human consumption. Always consult a qualified healthcare professional before considering any compounds.