Study teardown · PT-141 (bremelanotide, sold as Vyleesi) · FDA label and approval, phase 3 trials, 30 years of papers, SEC filings, FDA warning letters, FAERS and 10 registered trials · Sources checked October 24, 2026

Published October 24, 2026 · Updated October 24, 2026

PT-141 (bremelanotide): does it work, and does it work for men? It is FDA approved only as Vyleesi, for premenopausal women with low sexual desire, where it beat placebo by a modest margin. It has never been approved for men, and its maker stopped the men’s program in 2008 after FDA raised blood pressure concerns.

PT-141 is the code name for bremelanotide, a small ring-shaped peptide that switches on melanocortin receptors in the brain and skin.[1] In 2019, FDA approved it as Vyleesi, an injection used before sex, for premenopausal women with acquired, generalized hypoactive sexual desire disorder (HSDD).[2] In the two pivotal trials, about 25% of women on the drug and 17% on placebo had a meaningful rise in desire, and FDA found no difference in the number of satisfying sexual events.[2] The label says it is not for men, not for women after menopause, and “not indicated to enhance sexual performance.”[1] The most common side effect is nausea, reported by 40% of women in the trials.[1]

Why this matters now

On August 24, 2026, FDA posted five warning letters to online peptide sellers, and all five listed PT-141 among the products FDA described as unapproved new drugs.[17] On September 28, 2026, Palatin, the company that developed bremelanotide, said in its annual report that it does not intend to fund further trials of bremelanotide for weight loss on its own, and it flagged substantial doubt about its ability to continue as a going concern.[15] FDA’s adverse event database also now holds 50 reports in men, most often coded as off-label use, a use the label excludes.[18][1] And on October 14, 2026, FDA sent a policy on compounding certain peptides to the White House for review. Its list of peptides is not public.[22] We cover that policy here.

Thirty years in one table

Bremelanotide and melanotan II share the same seven-amino-acid ring. Bremelanotide ends in a free acid where melanotan II ends in an amide, according to the structures in the label and the 1996 paper.[1][6] They are different molecules, and only bremelanotide is FDA approved.[2][20]

What the approval trials showed

The two trials ran for 24 weeks and enrolled 1,247 premenopausal women, average age 39, who had lost sexual desire and were distressed by it. They followed a phase 2b trial in premenopausal women that compared doses.[1][5]

• Desire went up a little. On a desire scale from 1.2 to 6.0, scores rose 0.5 to 0.6 points on the drug and 0.2 points on placebo.[1] About 25% vs 17% of women had a rise of 1.2 points or more.[2]
• Distress went down a little. On a 0-to-4 distress scale, scores fell 0.7 points on the drug and 0.4 points on placebo.[1] About 35% vs 31% had a drop of at least 1 point.[2]
• Sex itself didn’t change. FDA found no difference in the number of satisfying sexual events, and said plainly that “Vyleesi does not enhance sexual performance.”[2]
• Many women stopped. About 40% left Study 1 early on the drug vs 13% on placebo, and 18% vs 2% stopped because of side effects.[1]
• A year of open-label use. Of 684 women who entered the extension, 272 finished it. Without a placebo group, it can’t show how much of any benefit came from the drug.[4]

Our arithmetic, from FDA’s rounded figures: the 8-point gap in desire responders means roughly 1 extra woman responded for every 12 or 13 treated.[2] The label tells women to stop after 8 weeks if they see no improvement.[2]

Does PT-141 work for men?

It has never been approved for men, and the label says so.[1] The men’s story is where PT-141 began, though:

• Early studies did show erections. Melanotan II caused erections in small studies in the 1990s, and PT-141 produced erections at the higher doses tested in Palatin’s 2004 studies, including in men who hadn’t responded well to Viagra.[6][7][8][9]
• Development stopped over blood pressure. By 2008, almost 2,000 people had received bremelanotide. Palatin said it stopped the program after FDA raised concerns about its benefit and risk as a first-line treatment for erectile dysfunction, “primarily because of increases in blood pressure observed in some patients.”[10]
• The biggest men’s trial has an Expression of Concern. A 2008 trial in 342 men who had not responded to sildenafil reported positive results. In January 2023, the journal published an Expression of Concern about that paper.[11] A 2008 trial of bremelanotide in women with arousal disorder by the same lead author was retracted. The journal’s notice says reviewers raised questions about its methods, results and statistics, and that the author did not respond to requests for the original data.[12]
• No trials in men are underway. Of the 10 bremelanotide trials on ClinicalTrials.gov, 8 enroll only women, and none lists erectile dysfunction.[19]
• Reports from men are coming in anyway. FDA’s adverse event database holds 50 reports in men linked to bremelanotide, and the most common term in them is “off label use” (37 reports).[18] These reports don’t prove the drug caused anything, but they show it is being used outside its label.

Side effects and safety

• Nausea. 40% of women had nausea, 13% needed anti-nausea medicine and 8% quit because of it. It was most common after the first dose. In a separate trial of 228 women, taking ondansetron (Zofran) beforehand didn’t help.[1]
• Blood pressure. Each dose briefly raises blood pressure, by up to 6 mmHg systolic, peaking 2 to 4 hours later and usually settling within 12 hours. The drug is contraindicated in uncontrolled high blood pressure or known heart disease.[1]
• Darkened skin and gums. About 1% of women in the trials developed dark patches on the face, gums or breasts. FDA said they did not go away in about half of them after stopping.[1][2] When people took it daily for 8 days, 38% developed patches. The risk is higher with darker skin.[1] This comes from MC1R, the same skin receptor behind melanotan’s tanning effect.[1][6]
• Interactions. It may slow stomach emptying, which can change how well some pills are absorbed. The label says to avoid it with naltrexone taken by mouth.[1]
• Pregnancy. Dog studies at high exposures showed fetal harm, and the label advises effective contraception.[1]
• Unregulated “melanotan-type” products. A 2017 review linked unlicensed melanotan I and II use to changing moles and four reported melanomas, while saying conclusive evidence of a link is lacking.[20] Those findings don’t transfer directly to approved Vyleesi, but they apply to products sold outside the approved supply chain, where purity and dose are unknown.

The weight-loss angle

Bremelanotide also acts on MC4R, a brain receptor that helps control appetite.[1] In two small, short Palatin studies in women with obesity, people on bremelanotide lost about 1.3 kg more than on placebo over 16 days.[16] In 2025, Palatin reported an 8-week phase 2 study combining it with tirzepatide (Zepbound): 4.4% weight loss vs 1.6% in the placebo group, according to the company’s press release. Its CEO said the study “was not designed to optimize weight loss,” and the results are topline company data, not a peer-reviewed paper.[14] In September 2026, Palatin said it would not fund further trials of this program on its own and is focusing on more selective MC4R drugs designed to cause less skin darkening.[15] No bremelanotide product is approved for weight loss.[1]

What a careful reader should notice

These points are our analysis of the cited sources.

1. The approval is narrow. Vyleesi is approved for one diagnosis in one group: premenopausal women with acquired, generalized HSDD.[1] Claims about men, libido in general or sexual performance go beyond it.
2. The benefit is modest. Most women on the drug didn’t reach FDA’s responder threshold, and placebo responses were substantial.[2]
3. Dropout matters. When 40% of the drug group leave early, partly because of nausea, the women who stay are not a random sample.[1]
4. The men’s evidence is old and thin. The men’s studies are early-phase, and the largest has an Expression of Concern. The men’s program was discontinued in 2008.[8][9][10][11]
5. Who paid. The phase 3 trials were funded by Palatin and AMAG, and the obesity data come from Palatin employees and press releases.[3][14][16] That doesn’t make them wrong, but independent replication is limited.
6. A legal path exists that most peptides lack. Federal law lets pharmacies compound from bulk substances that are components of FDA-approved drugs, and bremelanotide is one. Other conditions apply, including limits on copying approved products.[21] That differs from peptides like BPC-157 that are in no approved drug. This is our reading of the statute, not legal advice. Vials sold as “research use only” are a separate matter, and FDA’s August letters treat PT-141 sold that way as an unapproved drug.[17]

Frequently asked questions

Is PT-141 FDA approved?

Yes, but only as Vyleesi, a bremelanotide injection for premenopausal women with acquired, generalized hypoactive sexual desire disorder. It is not approved for men, for women after menopause or to enhance sexual performance.[1][2]

Does PT-141 work for men?

Small studies in the 2000s found erections in men at higher doses, but PT-141 was never approved for men. Its developer stopped the men’s program in 2008 after FDA raised blood pressure concerns, and no trial in men is listed as underway.[8][9][10][19]

How well does PT-141 work for women?

Modestly. In the phase 3 trials, about 25% of women on bremelanotide vs 17% on placebo had a meaningful rise in desire, and FDA found no difference in the number of satisfying sexual events.[2]

What are the side effects of PT-141?

Nausea affected 40% of women in the trials, followed by flushing (20%), injection site reactions (13%) and headache (11%). It briefly raises blood pressure after each dose, and about 1% developed darkened skin or gums that didn’t always fade.[1][2]

Is PT-141 the same as melanotan II?

No. They are closely related, sharing the same ring of seven amino acids, but they differ at one end of the molecule. Melanotan II is not approved, while bremelanotide is approved as Vyleesi.[1][6]

Does PT-141 cause weight loss?

It isn’t approved for that. Small company studies found modest short-term weight loss, alone and with tirzepatide, and Palatin said in September 2026 that it won’t fund further trials of the combination on its own.[14][15][16]

Is “research” PT-141 legal to sell?

FDA’s August 24, 2026 warning letters treat PT-141 sold online by those companies as an unapproved new drug.[17] Prescribed Vyleesi and, under certain conditions, pharmacy-compounded bremelanotide are different, regulated products.[1][21]

Bottom line

PT-141 is one of the few popular peptides with a real FDA approval, solid phase 3 trials and a full label.[1][3] The approval is narrow, though, and the benefit modest: a small edge over placebo in desire and distress for premenopausal women, with nausea in 40% and many dropouts.[1][2] For men, the evidence is early, its largest trial has an Expression of Concern, and the program stopped over blood pressure.[10][11] Claims that it works for everyone go further than the evidence.

This page analyzes FDA documents, published trials, SEC filings and registry records. It is not medical or legal advice and does not recommend any medication or dose. Vyleesi is approved only for premenopausal women with acquired, generalized HSDD. Charts were rebuilt by Jabbit from the sources cited in each caption.