What it is
PT-141 is also called bremelanotide. It is a short chain of amino acids (a peptide) made in a lab. It has seven amino acids, and six of them are joined in a ring. It is almost the same as another peptide called Melanotan II. The only difference is one small chemical group at the end of the chain.
Like Melanotan II, it switches on melanocortin receptors. These receptors are found on skin cells that make color (pigment). They are also found on nerve cells in the brain.
The approved product is called Vyleesi. It comes as a single-dose auto-injector (a pen that injects for you). It is given under the skin only when needed. In the United States, it is approved for one use only. That use is low sexual desire that causes distress in women who have not been through menopause. The problem must not be caused by another health condition, a relationship problem or a medicine. No one knows how it works for this.
Bremelanotide (Ac-Nle-cyclo[Asp-His-D-Phe-Arg-Trp-Lys]-OH, C50H68N14O10, 1025.2 g/mol free base) is the C-terminal carboxylic acid counterpart of Melanotan II. The label describes it as a non-selective melanocortin receptor agonist with an order of potency MC1R, MC4R, MC3R, MC5R, MC2R, and states that MC1R and MC4R binding is most relevant at therapeutic doses. MC4R is widely expressed in the central nervous system, including hypothalamic circuits linked to sexual motivation; the label states that the mechanism in HSDD is unknown. MC1R activation on melanocytes accounts for the focal hyperpigmentation.
Pharmacokinetics (label): after 1.75 mg subcutaneously, mean Cmax 72.8 ng/mL and AUC 276 h·ng/mL, median Tmax about 1 hour, absolute bioavailability about 100%, 21% protein binding, volume of distribution about 25 L, and mean terminal half-life about 2.7 hours. Elimination is by hydrolysis of amide bonds; 64.8% of a radiolabelled dose was recovered in urine and 22.8% in faeces.
Who made it and when
Bremelanotide came out of earlier work on Melanotan II at the University of Arizona. Melanotan II was a tanning compound. Researchers noticed that men given it had erections they did not expect. Palatin Technologies patented bremelanotide in 1999. They first tested it as a nasal spray in men with erection problems.
Later, the company switched to testing it in women. They also switched to an injection under the skin. Palatin ran the two main trials. In 2017, it gave North American rights to a company called AMAG Pharmaceuticals. The FDA approved Vyleesi on 21 June 2019. AMAG gave the rights back to Palatin in 2020. In December 2023, Palatin sold the product to Cosette Pharmaceuticals. Cosette holds the approval today.
US 6,579,968 (priority June 1999, granted June 2003, assigned to Palatin) claims Ac-Nle-cyclo(-Asp-His-D-Phe-Arg-Trp-Lys)-OH and its salts for sexual dysfunction; it has expired. Early clinical work used intranasal PT-141: Diamond et al. (Int J Impot Res 2004) reported median Tmax 0.5 hours, half-life 1.85–2.09 hours, and significant erectile responses above 7 mg in healthy men and sildenafil-responsive men with erectile dysfunction. The programme later switched to subcutaneous dosing in premenopausal women; a randomised, placebo-controlled dose-finding trial in premenopausal women (Clayton et al., Womens Health 2016) preceded Phase 3.
Palatin sponsored the two identical Phase 3 RECONNECT trials (Studies 301 and 302), started January 2015. AMAG obtained exclusive North American rights in 2017 and filed the NDA; FDA approved NDA 210557 on 2019-06-21 as a new molecular entity. The AMAG agreement ended in 2020, and Palatin completed the sale of Vyleesi to Cosette for USD 12 million upfront plus sales milestones in December 2023. Drugs@FDA lists Cosette as the application holder.
What the data say
Two matching trials included about 1,270 women who had not been through menopause. All had low desire for a long time. Women were assigned by chance to Vyleesi or a dummy treatment (placebo). The trials lasted 24 weeks.
Compared with placebo, women using Vyleesi had a small rise in desire. They also had a small drop in distress about low desire. The desire scale runs from 1.2 to 6. On average, Vyleesi added about a third of a point more than placebo. Most women used it two or three times a month.
Side effects were common. Four in ten had nausea (feeling sick to the stomach). It usually started within an hour of a dose. It was most common after the first dose. About one in five had flushing (a warm, red face). Blood pressure went up for a short time after each dose. Some women who used it often got dark patches on the face, gums or breasts. These patches did not always fade.
A 2026 label update added a breast-milk study: after one dose in 10 breastfeeding women, only a tiny amount of the drug reached the milk (about 0.13% of the mother’s dose, adjusted for weight), and none could be measured 24 hours later.
RECONNECT (Kingsberg et al., Obstet Gynecol 2019): 1,267 women randomised 1:1 to bremelanotide 1.75 mg subcutaneously as needed or placebo for 24 weeks; 1,247 in the safety and 1,202 in the modified intent-to-treat population; mean age 39, 85.6% white, 96.6% at US sites. Co-primary endpoints were change in the FSFI desire domain (range 1.2–6.0) and FSDS-DAO item 13 (range 0–4). Treatment differences for desire were +0.30 (Study 301) and +0.42 (Study 302), integrated +0.35 (all P under .001); for distress −0.37 (P under .001) and −0.29 (P=.005), integrated −0.33. The label reports no difference from placebo in the number of satisfying sexual events, a secondary endpoint, and more early discontinuation on bremelanotide.
Safety (label, n=627 vs 620): nausea 40.0% vs 1.3%, flushing 20.3% vs 0.3%, injection-site reactions 13.2% vs 8.4%, headache 11.3% vs 1.9%, vomiting 4.8% vs 0.2%. Blood pressure rose by up to 6/3 mmHg, peaking 2–4 hours after dosing and returning to baseline within about 12 hours. Focal hyperpigmentation occurred in 1% at up to 8 doses a month and 38% after 8 consecutive daily doses. The label advises stopping after 8 weeks if there is no improvement.
Lactation (label 10/2026, from NCT06867835, n=10): after a single 1.75 mg subcutaneous dose in healthy lactating women 10 days to 6 months postpartum, the mean total amount of bremelanotide in breast milk over 24 hours was estimated at 0.000152 mg, the relative infant dose was 0.132% of the weight-adjusted maternal dose, and milk concentrations were not measurable (below 1 ng/mL) at 24 hours in all samples. Toledo et al. (J Minim Invasive Gynecol 2026;33:16-33.e3, PMID 40543759), a systematic review and meta-analysis of 36 studies (26 RCTs), found that bremelanotide improved total FSFI and the desire and arousal subscales and reduced distress; Ashour et al. (Front Med 2026;13:1789809, PMID 42254382) reviewed 9 completed HSDD trials on ClinicalTrials.gov and found flibanserin and bremelanotide the most studied drugs. Outside HSDD, Palatin’s Phase 2 study of bremelanotide 1.25 mg daily with tirzepatide 2.5 mg weekly in obesity (NCT06565611, 96 randomised) has posted no results; the company reported 4.4% versus 1.6% weight loss at 8 weeks in a March 2025 press release, which is not peer reviewed. A Korean Phase 3 bridging study (NCT04943068, n=193) and a Phase 2b open-label study in diabetic kidney disease (NCT05709444, n=16) are complete with no results posted.
Regulatory picture
There are three separate points here.
Approval: The FDA approved bremelanotide as Vyleesi. It is only for women before menopause who have lost sexual desire in general (called HSDD). The label says it is not approved for women after menopause. It is not approved for men. It is not approved to boost sexual performance.
Pharmacy-made versions: An approved product exists. So pharmacies may not make copies of it. A US pharmacy may still use it as an ingredient in a mix made for one patient, if it is not a copy. But the FDA does not check these mixes.
Enforcement: In August 2026, the FDA sent warning letters to online sellers. These sellers sold peptides labelled “for research” and listed PT-141. The FDA said these were unapproved drugs meant for people. Products sold online as PT-141 are not Vyleesi.
Approval: approved. NDA 210557, approved 2019-06-21; label revised 10/2026 (supplement S-005, approved 2026-10-22 on the final report of postmarketing requirement 3635-3, adding lactation data to section 8 and the patient information; dosing, contraindications and warnings unchanged). Limitations of use: not indicated in postmenopausal women or men, or to enhance sexual performance. The label contraindicates it in uncontrolled hypertension or known cardiovascular disease, advises against it in patients at high cardiovascular risk, and states that no more than one dose should be given in 24 hours and that more than 8 doses a month is not recommended.
Compounding: recorded as restricted, meaning copies of Vyleesi are not permitted. Because bremelanotide is a component of an FDA-approved drug, section 503A allows it as a bulk ingredient for patient-specific preparations that are not essentially copies; those preparations are not FDA-reviewed. It is not among the substances FDA placed in Category 2.
Enforcement: FDA warning letters dated 2026-08-24 to online peptide sellers named PT-141 (bremelanotide) among unapproved new drugs, rejecting “research use only” labelling where websites made human-use claims; five letters named PT-141 (Royal Peptides, Peak Performance Peptides, Tex Peptides, Peptide Partners and NuScience Peptides). No FDA action against the approved product has been reported.
