PT-141 (Bremelanotide): Research, Evidence, and Context

PT-141, also called bremelanotide, is a synthetic cyclic heptapeptide that activates several melanocortin receptors. The evidence base spans receptor pharmacology, animal experiments, and studies of the regulated US medicine Vyleesi. None of those sources establishes clinical use, quality, or stability for a separate lyophilized Bergdorf Bio research vial. DailyMed, Vyleesi prescribing information

This guide keeps those evidence layers distinct. It describes the labeled chemical identity of bremelanotide, the questions explored in experimental research, and the findings reported for a specific approved product. It does not provide dosing, preparation, or administration instructions for the research material.

What are PT-141 and bremelanotide?

PT-141 is a development name for bremelanotide, not the name of a different molecule. The current Vyleesi label describes bremelanotide acetate as a synthetic cyclic heptapeptide with a free carboxylic acid terminus and an acetylated amino terminus. It gives the sequence Ac-Nle-cyclo-(Asp-His-D-Phe-Arg-Trp-Lys-OH) and a molecular weight of 1025.2 Da for the free base. These details are useful reference points for chemical identity, but they are label data for bremelanotide, not a certificate of identity for any individual vial. DailyMed, section 11

A researcher comparing spectra, chromatographic behavior, or mass transitions has to account for cyclization, terminal modifications, salt form, and the method used. A shared name or nominal sequence alone cannot demonstrate lot-specific identity, purity, sterility, or pharmaceutical equivalence. Those are separate questions requiring evidence from the material and method actually under examination.

The reported mass also needs a stated reference form. The label distinguishes bremelanotide acetate from the free base and notes variable stoichiometry for the acetate component. A value can therefore be accurate in one chemical context and inapplicable in another. Stating whether an observation concerns the free base, acetate, or an analytical sample prevents false disagreements between datasets. DailyMed, section 11

That distinction is especially important here. Vyleesi is a sterile, clear solution supplied in a prefilled single-dose autoinjector; the Bergdorf Bio material discussed in this guide is a separate lyophilized research vial. The finished medicine's formulation, excipients, device, manufacturing controls, and regulatory evaluation do not characterize the research vial. DailyMed, sections 3 and 11

How does PT-141 interact with melanocortin receptors?

Bremelanotide is a nonselective agonist of multiple melanocortin receptors, rather than a ligand confined to one subtype. The Vyleesi label lists a relative potency order of MC1R, MC4R, MC3R, MC5R, then MC2R, and highlights MC1R and MC4R in the approved-product context. DailyMed, section 12.1

The receptor subtypes provide different research anchors. The label notes MC1R expression on melanocytes and links its activation to melanin expression and increased pigmentation. It also notes that MC4R-expressing neurons occur in several areas of the central nervous system. Yet the label explicitly states that the mechanism by which Vyleesi works in its approved indication is unknown. It would therefore overstate the evidence to assign the complete clinical effect to MC4R, or to any single subtype. DailyMed, section 12.1

For experimental interpretation, receptor expression, ligand concentration, assay design, and readout should be reported independently. A binding result is not a clinical outcome, and a behavioral observation does not on its own identify one receptor as causal. Functional controls, subtype-selective comparators where appropriate, and genetic approaches can make an attribution more credible. They do not remove the product-specific limit on clinical interpretation.

Relative potency is not absolute selectivity. Highlighting MC1R and MC4R does not rule out contributions from the other melanocortin receptors listed in the label. That is why a useful PT-141 research question identifies the receptor system and the measured signal before drawing a conclusion, while preserving the regulator's conclusion that the clinical mechanism of Vyleesi remains unknown. DailyMed, section 12.1

What does preclinical research show about bremelanotide?

Preclinical evidence is hypothesis-generating and depends heavily on the model. In a study of female rats, PT-141 was examined as an experimental melanocortin agonist rather than as a finished medicine. The authors reported selective increases in certain solicitation and approach behaviors, while other components of sexual behavior did not change in the same pattern. That result supported a hypothesis that central melanocortin signaling can modulate particular motivational components of behavior. It did not establish an equivalent human effect or a universal mechanism across species. Pfaus et al., 2004

A 2025 study in female Syrian hamsters illustrates why the distinction matters. It mapped MC3R and MC4R messenger RNA in the mesolimbic dopamine system and found no bremelanotide-associated change in the measured receptor mRNA. In that model, bremelanotide also did not enhance the measured reward effect of sexual experience. The authors discussed their findings as inconsistent with a simple account in which bremelanotide acts through the ventral tegmental area to nucleus accumbens reward circuit. Borland et al., 2025

For laboratory work, the practical scientific lesson is to predefine endpoints and controls, and to distinguish receptor activation, motivation, and behavior in the analysis. No measured mRNA change can rule out every possible receptor contribution, just as detected mRNA cannot prove receptor function in a given outcome. Neither study evaluated the Bergdorf Bio research vial, so neither can validate that material for a clinical or non-research purpose. Pfaus et al., 2004 Borland et al., 2025

What do clinical studies of bremelanotide report?

The strongest efficacy evidence comes from the two identically designed RECONNECT phase 3 trials. They were randomized, double-blind, and placebo-controlled studies in premenopausal women with acquired, generalized hypoactive sexual desire disorder. Co-primary outcomes were the desire domain of the Female Sexual Function Index and an item measuring distress related to low desire. Kingsberg et al., 2019

Compared with placebo, both trials reported statistically significant group differences for sexual desire and associated distress. In the integrated analysis, the estimated mean-change differences were 0.35 points for the desire domain and minus 0.33 points for the distress item. These are group-level changes on validated self-report scales, not an individual guarantee. Kingsberg et al., 2019

Earlier development research included a randomized, placebo-controlled dose-finding study with 327 participants in the efficacy analysis. Its pooled analysis reported changes in event-based outcomes and function and distress scales across selected study arms. Multiple arms, a shorter study period, and a broader diagnostic population make it developmental evidence rather than a substitute for the confirmatory RECONNECT programme. Clayton et al., 2016

Still earlier studies used other designs and formulations. One small double-blind crossover study in 18 premenopausal women examined intranasal bremelanotide and reported preliminary changes in subjective responses. A separate early study in men examined intranasal PT-141 using physiological measurement. These are historical development studies, not evidence that an intranasal product is approved or that any route is appropriate for the research vial. Diamond et al., 2006 Diamond et al., 2004

What does Vyleesi approval mean for PT-141 research material?

The US Food and Drug Administration approved Vyleesi in 2019 for a narrowly defined indication: acquired, generalized hypoactive sexual desire disorder in premenopausal women when low desire causes marked distress or interpersonal difficulty and is not attributable to specified alternative factors. The Vyleesi label also says the medicine is not indicated for postmenopausal women, for men, or to enhance sexual performance. These are statements about the regulated finished medicine and its labeled indication. FDA approval package, NDA 210557 DailyMed, section 1

Regulatory review assessed a specified product, its composition, presentation, manufacturing, labeling, and supporting evidence. The fact that Vyleesi contains bremelanotide does not make another material bearing the same molecular name a medicine, a generic equivalent, or clinically validated. An approval date and a positive benefit-risk decision cannot serve as a general quality mark for every sample called PT-141. FDA multidisciplinary review, NDA 210557

Vyleesi data can inform interpretation of the tested medicine's human pharmacology but cannot establish the research vial's stability, sterility, release testing, or suitability for use. The lyophilized Bergdorf Bio research vial is not Vyleesi, the approved finished medicine, and is neither clinically nor pharmaceutically equivalent to it, so Vyleesi's approval, efficacy and safety findings, dosing, quality, and regulatory status do not transfer to the vial.

No cited study examined the specific Bergdorf Bio material. For broader context on reading peptide evidence cautiously, see the Bergdorf Bio guide library. DailyMed, sections 3 and 11

Which pharmacokinetic findings are documented for bremelanotide?

The label reports pharmacokinetic findings for the subcutaneous Vyleesi solution, not for research material. In that product-and-route context, the median time to maximum plasma concentration was about one hour. The mean terminal half-life was about 2.7 hours, with a reported range of 1.9 to 4.0 hours, and about 21% of bremelanotide was bound to human serum proteins. DailyMed, section 12.3

The label identifies hydrolysis of amide bonds in the cyclic peptide as the primary metabolic pathway. In studies using radiolabeled material, radioactivity was recovered in urine and feces. Those observations describe metabolism and elimination in the investigated Vyleesi setting. They are not measurements of chemical stability for a lyophilized vial, nor do they characterize a laboratory preparation made from it. DailyMed, section 12.3

A plasma half-life is not an intrinsic material constant comparable to molecular mass. Species, route, formulation, sampling matrix, and analytical method all affect the value. The 2.7-hour figure must therefore remain attached to the labeled subcutaneous Vyleesi context. It cannot be treated as route-independent kinetics, research-vial stability, or a basis for a human schedule. The half-life calculator hub explains elimination concepts in general terms and does not replace product-specific evidence.

An older intranasal study in men reported a mean terminal half-life between 1.85 and 2.09 hours. That separate result shows why values from different study formats should not be merged. It does not establish intranasal approval, and it has no bearing on the suitability or stability of the Bergdorf Bio research vial. Diamond et al., 2004

Which safety signals were observed for the approved medicine?

Safety findings must remain tied to the clinical product and programme that generated them. An integrated analysis covering 3,500 participants across 43 studies reported that nausea, flushing, headache, and injection-site reactions occurred more often with bremelanotide than with placebo during the pooled double-blind phase 3 data. Small, transient increases in blood pressure were also reported. These are clinical-programme observations, not a transferable adverse-event rate for another material. Clayton et al., 2022

The current Vyleesi label particularly highlights transient increases in blood pressure with reductions in heart rate, focal hyperpigmentation, and nausea. It lists nausea, flushing, injection-site reactions, headache, and vomiting among the most common adverse reactions. The pigmentation warning is pharmacologically consistent with the label's description of MC1R on melanocytes and its association with increased melanin expression, but it does not make a mechanistic association a complete safety explanation. DailyMed, sections 5, 6, and 12.1

A randomized ambulatory blood-pressure study documented small, time-limited hemodynamic changes in its investigated clinical setting. Its purpose was to inform cardiovascular assessment of the development programme, not to certify another formulation or source material. White et al., 2017

The open-label RECONNECT extension has a different evidentiary weight. Of 856 eligible participants, 684 enrolled and 272 completed the extension; the descriptive analysis reported no new safety signals. Without blinded placebo control, it supplies longer-term observation rather than a replacement for the controlled core trials. None of these data establish the same risk profile, or safety, for a lyophilized research vial. Simon et al., 2019

Where does the current PT-141 evidence stop?

The strongest clinical efficacy evidence answers a limited question: whether two patient-reported outcomes changed differently from placebo, on average, in a defined trial population. It does not show effectiveness for men, postmenopausal women, people without the studied disorder, or sexual performance enhancement. The Vyleesi label expressly limits its indication accordingly. A responsible account names the population and comparator before using broad terms such as “effective.” Kingsberg et al., 2019 DailyMed, section 1

There is also a mechanistic limit. The receptor profile is documented, and MC4R-expressing neurons occur in the central nervous system, but the approved-product label says the mechanism of Vyleesi's clinical effect is unknown. Preclinical work supports questions, not a single settled explanation: one rat model identified changes in selected approach-related behaviors, whereas a later hamster study did not find enhanced measured sexual reward or altered measured melanocortin-receptor mRNA. Pfaus et al., 2004 Borland et al., 2025

Patient-reported outcomes add another interpretive boundary. The tools are appropriate to the questions their studies asked, but they are not direct receptor assays and cannot forecast an individual's response. Statistical significance is also different from a guaranteed or uniform individual benefit. Claims should remain at the level the design can support.

Finally, the Bergdorf Bio research vial has no clinical evidence in the cited trials. No listed publication studied that particular material. This is not a minor caveat: it is the central limit on every attempted transfer from receptor data, animal experiments, or Vyleesi clinical research to a separate research vial.

How should a lyophilized PT-141 research vial be classified?

A lyophilized PT-141 research vial should be documented as a laboratory material, not described as a simplified version of Vyleesi. Researchers should keep the identity of the received material, lot documentation, receipt condition, analytical method, matrix, controls, and acceptance criteria distinct in their records. The labeled sequence and molecular mass can inform an identity question, but they do not replace a lot-specific measurement. DailyMed, section 11

Storage or stability language from the medicine should not be copied to the research vial. The label concerns a sterile solution with specified excipients, packaging, and a product-specific presentation. A lyophilized vial has a different matrix and container system. Without product-specific stability data, claims about shelf life after laboratory handling, permissible temperature cycling, or microbiological status would be speculative. DailyMed, sections 11 and 16

A concise scientific distinction is useful: bremelanotide is the active ingredient in the approved medicine Vyleesi; the lyophilized material discussed here is not Vyleesi and is not a clinical product. Any account of clinical findings, adverse reactions, or pharmacokinetics should name the Vyleesi or study context that was actually investigated.

The appropriate value of a research vial lies in controlled questions about identity, analytics, and receptor pharmacology, rather than an untested use outside the laboratory. It must not be represented as interchangeable with the approved medicine. Its Research Use Only status means it is not intended for human or veterinary use, diagnosis, treatment, or prevention.

Which common questions remain about PT-141 and bremelanotide?

Are PT-141 and bremelanotide the same molecule?

Yes. PT-141 is a commonly used development name for bremelanotide, which the Vyleesi label describes as a synthetic cyclic heptapeptide. The shared molecular name does not make different products pharmaceutically equivalent. DailyMed, section 11

Which melanocortin receptors does bremelanotide activate?

The current Vyleesi label lists MC1R, MC4R, MC3R, MC5R, and MC2R in decreasing relative potency. It describes bremelanotide as nonselective, while the mechanism of Vyleesi's clinical effect remains unknown. DailyMed, section 12.1

Is the Bergdorf Bio research vial Vyleesi?

No. Vyleesi is a labeled sterile solution in a prefilled single-dose autoinjector, whereas the material discussed here is a separate lyophilized research vial. Vyleesi approval, formulation, sterility, and clinical data do not transfer to that material. DailyMed, sections 3 and 11

What is the documented terminal half-life of bremelanotide?

For the marketed subcutaneous Vyleesi solution, the label reports a mean terminal plasma half-life of about 2.7 hours, ranging from 1.9 to 4.0 hours. It is not a research-vial stability measure, a route-independent value, or a basis for an application plan. DailyMed, section 12.3

Do the studies show general sexual-performance enhancement?

No. The phase 3 findings concern a defined disorder and population, and the Vyleesi label says the medicine is not indicated for sexual-performance enhancement. No clinical effect has been studied for the Bergdorf Bio research vial. Kingsberg et al., 2019 DailyMed, section 1

For research use only. Not for human consumption. Scientific editing: Dr. Sieglinde Klaus