Research and laboratory use only. Not for human consumption.
PT-141
PT-141, now known by the generic drug name bremelanotide, is a cyclic melanocortin peptide originally developed from melanotan-II research. It acts as a melanocortin receptor agonist and became notable because its effects on sexual desire and arousal arise predominantly through central nervous system signalling rather than through a direct peripheral vasodilatory mechanism.
What is PT-141?
PT-141 is the original investigational development code for the peptide now known as bremelanotide.
Bremelanotide is a cyclic melanocortin peptide derived from research into analogues of alpha-melanocyte-stimulating hormone and the synthetic peptide melanotan-II.
It acts as an agonist at several melanocortin receptors, with central MC4 receptor signalling considered particularly relevant to its effects on sexual desire.
The melanocortin system is involved in a broad range of physiological processes including pigmentation, appetite, energy balance, autonomic regulation and sexual behaviour.
PT-141 became scientifically important because researchers observed effects on sexual arousal while studying related melanocortin peptides.
Clinical development eventually focused on female hypoactive sexual desire disorder, resulting in approval of bremelanotide as the prescription medicine Vyleesi in the United States in 2019.
Why is it called PT-141?
PT-141 was the investigational code used during development of the compound.
It is not an abbreviation describing the peptide's amino-acid sequence or receptor target.
As the molecule progressed through pharmaceutical development it received the generic name bremelanotide.
The commercial FDA-approved formulation contains bremelanotide acetate and is marketed under the brand name Vyleesi.
Research-product use of the term PT-141 and pharmaceutical use of the name bremelanotide therefore refer to the same active peptide, although formulation, purity and regulatory status of individual products are separate matters.
A sexual-function effect discovered during melanocortin research
PT-141 emerged from research into melanocortin peptide analogues originally investigated for pigmentation and related biological effects.
From melanotan-II to bremelanotide
Melanocortin peptide research initially focused heavily on pigmentation and the biological activity of alpha-MSH analogues.
During development of the synthetic cyclic peptide melanotan-II, researchers observed effects involving sexual arousal and erectile responses.
These findings encouraged development of a related compound intended to retain sexual-function pharmacology while separating it from the pigmentation focus of the original programme.
The resulting molecule became known as PT-141.
Early clinical research investigated both male erectile dysfunction and female sexual dysfunction.
Pharmaceutical development subsequently concentrated on acquired, generalized hypoactive sexual desire disorder in premenopausal women, ultimately resulting in U.S. approval of bremelanotide in 2019.
Peptide structure
Bremelanotide is a modified cyclic peptide based on melanocortin pharmacology. Cyclization helps constrain the peptide into a biologically active conformation.
What is the melanocortin system?
Melanocortins are a family of endogenous signalling peptides derived from the proopiomelanocortin precursor.
Their receptors are G-protein-coupled receptors distributed throughout the central nervous system and peripheral tissues.
Bremelanotide is not perfectly selective for a single melanocortin receptor. It activates several melanocortin receptor subtypes.
However, MC4R signalling is considered especially relevant to the compound's effects on sexual desire at therapeutic exposure.
MC4 receptors are expressed in brain regions including hypothalamic pathways involved in motivation, reproduction, appetite and autonomic regulation.
Why has PT-141 been studied?
PT-141 became an important research compound because melanocortin signalling provided a central nervous system approach to investigating sexual motivation and arousal.
Sexual Desire
Bremelanotide has been studied extensively in neural pathways involved in sexual motivation and desire.
MC4R Biology
The molecule has contributed to research into melanocortin receptor regulation of sexual behaviour.
Female Sexual Dysfunction
Clinical development ultimately focused on acquired generalized HSDD in premenopausal women.
Male Erectile Research
Earlier studies investigated erectile responses in men, although this did not become the approved indication.
How does bremelanotide influence sexual desire?
The precise pathway connecting melanocortin receptor activation to the clinical effect is still not completely defined, but central MC4R signalling is considered a major component.
Receptor Activation
Bremelanotide activates multiple melanocortin receptor subtypes rather than acting through a single isolated receptor.
Central Nervous System
Its clinically relevant sexual-function effects are thought to originate largely within central neural circuits.
MC4R
MC4R signalling in hypothalamic regions is considered particularly relevant to female sexual desire.
Dopaminergic Interaction
Preclinical models suggest melanocortin activation can influence dopamine-related excitatory pathways associated with sexual motivation.
Early PT-141 clinical programmes examined erectile responses in men with and without erectile dysfunction before the development programme shifted primarily toward female HSDD.
PT-141 was also studied in men
Early human development of PT-141 included studies examining erectile responses in men.
This was scientifically notable because the mechanism was different from phosphodiesterase-5 inhibitors such as sildenafil, which act primarily through peripheral nitric-oxide signalling.
Melanocortin agonists instead target central neural pathways involved in sexual response.
Some early clinical studies reported measurable erectile responses following PT-141 exposure, supporting biological activity in men.
However, development for male erectile dysfunction did not become the approved indication.
The approved U.S. prescribing information specifically states that Vyleesi is not indicated for men.
The RECONNECT trials
Regulatory approval was supported principally by two similarly designed randomized Phase III studies evaluating bremelanotide in premenopausal women with acquired generalized HSDD.
RECONNECT 301 & 302
Two randomized, double-blind, placebo-controlled multicentre studies evaluating bremelanotide in premenopausal women with HSDD.
The RECONNECT programme consisted of two nearly identical Phase III trials.
A total of 1,267 women were randomized across the two studies.
Participants were premenopausal women diagnosed with acquired, generalized hypoactive sexual desire disorder.
The coprimary efficacy endpoints measured changes in sexual desire and distress associated with low desire.
Bremelanotide produced statistically significant increases in desire scores and reductions in distress compared with placebo across the integrated studies.
A subsequent open-label extension followed participants for longer-term safety and effectiveness assessment.
It is also important to recognize that later independent analyses have questioned the magnitude and clinical interpretation of some RECONNECT efficacy outcomes. Statistical significance therefore should not be interpreted as meaning that every participant experiences a large clinical benefit.
Bremelanotide is an FDA-approved medicine
This distinguishes PT-141 from many research peptides. The active molecule has completed a pharmaceutical development programme and received regulatory approval for one defined patient population and indication.
Vyleesi — bremelanotide acetate
The U.S. Food and Drug Administration approved Vyleesi in June 2019.
The approved indication is treatment of premenopausal women with acquired, generalized hypoactive sexual desire disorder where low sexual desire causes marked distress or interpersonal difficulty.
The diagnosis covered by the indication is not due to a co-existing medical or psychiatric disorder, relationship problems or the effects of medication or another drug substance.
The approved prescribing information also states that bremelanotide is not indicated for postmenopausal women or men and is not indicated simply to enhance sexual performance .
What adverse effects were observed clinically?
Because bremelanotide progressed through controlled Phase III studies and regulatory review, considerably more human safety information exists than for most research peptides.
Nausea
Nausea was the most frequently reported adverse reaction in the Phase III programme and occurred substantially more often than with placebo.
Flushing
Flushing was another commonly reported treatment-emergent adverse effect.
Blood Pressure
Bremelanotide can produce temporary increases in blood pressure accompanied by temporary reductions in heart rate.
Hyperpigmentation
Focal darkening of areas including the face, gums and breasts has been reported, particularly with more frequent exposure.
The FDA-approved prescribing information contraindicates Vyleesi in patients with uncontrolled hypertension or known cardiovascular disease because of its transient effects on blood pressure and heart rate. This regulatory information relates to the approved pharmaceutical product and should not be interpreted as administration guidance for research material.
How strong is the evidence?
Bremelanotide has a much stronger clinical evidence base than most compounds commonly described as research peptides, but the strength of evidence differs greatly depending on the proposed use.
Molecular Pharmacology
Melanocortin receptor agonism and peptide-receptor interactions are well characterized.
Human Pharmacology
Multiple controlled studies establish biological activity in humans.
Phase III HSDD Evidence
Two large randomized Phase III studies demonstrated statistically significant effects on regulatory efficacy endpoints.
Other Uses
Claims involving general libido enhancement, male sexual performance or other uses are outside the approved indication and have a different evidence base.
What should not be assumed?
Factors affecting PT-141 stability
Bremelanotide is a cyclic peptide. Laboratory storage conditions should be based on analytical documentation for the exact chemical form and formulation rather than inferred from the commercial pharmaceutical product.
Temperature
Temperature can influence peptide degradation and long-term molecular integrity.
Moisture
Humidity can affect lyophilized peptide preparations and physical stability.
Solution Conditions
Solvent, buffer, pH and concentration can alter peptide stability after preparation in solution.
Chemical Form
Free base, acetate form, purity and formulation should be specified in the analytical documentation for research material.
Clinically validated melanocortin agonist with a specific FDA-approved indication
Bremelanotide is unusual among compounds commonly encountered in peptide research because the active molecule has completed extensive human clinical development and received regulatory approval.
The FDA-approved medicine Vyleesi is indicated specifically for premenopausal women with acquired, generalized HSDD meeting the diagnostic criteria described in the approved label.
It is not approved in the United States for men, postmenopausal women or general enhancement of sexual performance.
The approved pharmaceutical status of Vyleesi should also not be interpreted as approval of independently manufactured research PT-141 material.
ASA Research Labs provides this page for scientific and educational purposes. Discussion of the FDA-approved medicine is intended to explain the compound's regulatory and scientific history and is not prescribing or administration advice.
Selected scientific references
Selected literature covering bremelanotide structure, melanocortin receptor biology, human sexual-function research, Phase III development and regulatory approval.
Scientific and regulatory information
This profile is provided for scientific and educational purposes. Bremelanotide is the active peptide in an FDA-approved prescription medicine for a specific indication in premenopausal women. Discussion of clinical trials, approved pharmaceutical use, investigational male research, receptor pharmacology or adverse effects does not constitute prescribing advice and does not establish that independently supplied PT-141 research material is equivalent to the approved pharmaceutical product. This page does not provide instructions for administration, dosing or unsupervised human use.