PT-141 (Bremelanotide): What the Evidence Shows

PT-141 is bremelanotide, and bremelanotide is an FDA-approved drug: Vyleesi, approved in June 2019 for one use only, acquired, generalized hypoactive sexual desire disorder (HSDD) in premenopausal women.^[1][2] The label states it is not for postmenopausal women, not for men, and “not indicated to enhance sexual performance.”^[1] In its two phase 3 trials it raised desire scores by a small amount more than placebo and did not increase satisfying sexual events at all.^[1] The version sold to men for erections comes from a development program that FDA’s concerns about blood pressure stopped in 2007.^[14]

PT-141, bremelanotide and Vyleesi are the same molecule

PT-141 was the development code used by Palatin Technologies. It began as an analog of melanotan II, a peptide from the University of Arizona that was tested for tanning and erections.^[3] Bremelanotide is the generic name, and Vyleesi is the brand: a 1.75 mg autoinjector now sold by Cosette Pharmaceuticals.^[1] Melanotan II itself was never approved. How it differs from the one approved tanning-related peptide is covered in melanotan versus the approved one.

Bremelanotide switches on melanocortin receptors. In order of potency, the label lists MC1R, MC4R, MC3R, MC5R and MC2R, and says binding at MC1R and MC4R matters most at the approved dose.^[1] MC4R is found throughout the brain. MC1R sits on the skin’s pigment cells, which is why skin darkening is on the label. The label is also direct about what is not known: “The mechanism by which VYLEESI improves HSDD in women is unknown.”^[1]

What the Vyleesi label allows

The dose limits are there for safety reasons. The label says doses taken close together “may increase the risk of additive effects on blood pressure,” and more frequent dosing raises the risk of skin darkening.^[1] Few women in the phase 3 program took more than 8 doses a month. The median was 10 injections over the full 24 weeks.^[1]

What the RECONNECT trials found

Approval rested on two identical 24-week trials, studies 301 and 302, together called RECONNECT. They randomized 1,267 premenopausal women with HSDD, average age 39, to bremelanotide or placebo, used as needed.^[4] There were two main measures. One was a desire score built from two questionnaire items, running from 1.2 to 6. The other was a single item on how often low desire bothered the woman, scored 0 to 4.^[1]

Both main measures were statistically significant in both trials.^[4] The size of the effect is the question. On the desire scale, the gap over placebo was about a third of a point on a scale under 5 points wide.^[4] Responder figures make it concrete: about 8 more women in every 100 reached a large desire improvement than on placebo, and about 4 more in every 100 reached a large drop in distress.^[2] The number of satisfying sexual events did not change on either drug or placebo.^[1] FDA put it plainly in its approval announcement: “Vyleesi does not enhance sexual performance.”^[2]

Far more women stopped bremelanotide early than stopped placebo.^[1] Of the women who finished the 24 weeks, 70% on bremelanotide went on to the open-label extension, against 87% of those on placebo.^[6] In the 52-week extension, 684 women started and 272 finished. The improvement held among those who stayed, but that part of the study had no placebo group, and its statistics were descriptive only.^[5]

The trials have a public critic. A psychologist who re-analyzed the FDA application data found that women on bremelanotide were about 12 times as likely to quit because of side effects (one extra quitter for every 6 treated), and argued that, counting who finished and who chose to continue, participants preferred placebo.^[8] A second paper reported that 8 of the 11 efficacy outcomes registered on ClinicalTrials.gov had not been published, and that effect sizes on those ranged “from nil to small.”^[9] The trial investigators, several of whom work for the drug’s developers, published a reply titled “Failure of a Meta-analysis.”^[10] Readers can weigh both. Nobody disputes the core numbers in the table above, which come from the label.

Side effects on the label

• Nausea. 40% of women on bremelanotide, against 1.3% on placebo. 13% needed anti-nausea medicine and 8% left the trials because of it. It usually eased with the second dose.^[1][6] Taking ondansetron 30 minutes beforehand did not reduce it in a 228-woman study.^[1]
• Flushing and headache. Flushing in 20% against under 1% on placebo; headache in about 11%.^[1][6]
• Blood pressure. Each dose raises blood pressure briefly, by up to 6 mmHg systolic and 3 mmHg diastolic, peaking 2 to 4 hours after the injection, with heart rate falling by up to 5 beats a minute. Both usually return to baseline within 12 hours.^[1] In a dedicated 24-hour monitoring trial of 397 women, the rise at 1.75 mg was about 3 mmHg over placebo.^[7]
• Skin darkening. Patches on the face, gums or breasts appeared in 1% of women dosing up to 8 times a month. In a study of daily dosing, 38% developed it within 8 days. It was more likely in women with darker skin.^[1] FDA said it did not go away in about half of those affected after they stopped.^[2]

PT-141 for men: the program that stopped

Bremelanotide was first developed for men, as a nasal spray for erectile dysfunction. The early studies, run or sponsored by Palatin, showed an effect on erections measured in a lab.

Then FDA weighed in. In late August 2007, according to Palatin’s annual report, FDA raised “serious concerns about the acceptable benefit/risk ratio” of moving the nasal spray into phase 3 as a first-line treatment for erectile dysfunction. Palatin wrote that FDA “questioned overall efficacy results and the clinical benefit” in both the general and diabetic populations, “citing blood pressure increases as its greatest safety concern.” Its partner, King Pharmaceuticals, ended the collaboration effective December 2007.^[14]

“Increases in blood pressure were observed in some patients receiving nasally administered bremelanotide, and this observed increase was a significant factor leading us to discontinue work on nasally administered bremelanotide as a first-line therapy for sexual dysfunction.”

— Palatin Technologies, annual report (Form 10-K) for the year ended June 30, 2009

Palatin blamed uneven absorption through the nose and switched to an injection, then took the injection forward in women.^[15] No phase 3 trial in men followed. The one large controlled trial in men that did reach a journal, the 2008 Safarinejad study, now carries an expression of concern.^[17] The same author’s bremelanotide trial in women was retracted by the Journal of Sexual Medicine, which said it could “no longer verify the results or methods as presented.”^[18]

So when PT-141 is offered to men for libido or erections, it rests on small lab studies from the early 2000s, company-reported phase 2 figures, and one trial whose journal has flagged it. Nothing in that record establishes a dose or a safety profile for men. The blood pressure problem that stopped the men’s program is the same effect that is on the women’s label today.^[1][14]

Compounded and “research” PT-141

Vyleesi is the only bremelanotide product FDA has reviewed. A compounded version from a pharmacy is not checked by FDA for dose, purity or sterility, and a vial sold “for research use only” has no prescriber or pharmacy standard behind it at all. What those labels mean legally is covered in are peptides legal. Forensic labs have identified bremelanotide in police-seized products sold to bodybuilders next to steroids and melanotan II.^[21]

FDA has also started naming it. At least 5 warning letters in our FDA letter tracker, the most recent dated August 2026, list “PT-141” among products FDA called unapproved new drugs, sold by “research peptide” websites alongside retatrutide and other injectables.

Off-label menus also tend to drop the label’s limits. The approved product is a fixed 1.75 mg dose, no more than once a day and no more than about twice a week on average. Daily use is exactly the pattern that produced skin darkening in 38% of women within 8 days.^[1]

Bremelanotide, weight loss and GLP-1 drugs

MC4R also controls appetite, so Palatin tested bremelanotide in women with obesity. In two short phase 1 studies run by the company, injections three times a day for 15 days cut food intake by about 400 calories a day and body weight by 1.3 kg more than placebo.^[19] That is a 16-day result at several times the approved dosing frequency. It is not a weight-loss treatment, and daily dosing carries the skin-darkening risk above.^[1]

For people already on a GLP-1 drug, the label point that matters is digestion. The Vyleesi label says it “may slow gastric emptying” and can reduce how fast and how much of an oral medicine is absorbed. It tells patients to avoid it with oral drugs that need a threshold level to work, such as antibiotics, and warns that it sharply lowers levels of oral naltrexone.^[1] The Wegovy label says the same about semaglutide: it “delays gastric emptying” and may affect absorption of oral medicines.^[20] No study has tested bremelanotide together with a GLP-1 drug. Both cause nausea, and both slow the stomach, so anyone combining them should tell the prescriber about both and expect oral medicines to be affected. How GLP-1 side effects compare is in which GLP-1 has the worst side effects.

Contraception is the other overlap. Vyleesi’s label asks women to use effective contraception while taking it.^[1] Some GLP-1 labels have their own warnings about birth control pills, set out in GLP-1s and hormonal birth control.

Where PT-141 sits on the peptide menu

Among the peptides sold by clinics and research-chemical sites, bremelanotide is unusual. It has a real trial record, because it became an approved drug, as the peptide menu shows by count. That record supports one use: modest help with low desire in premenopausal women who can tolerate the nausea. It does not support use in men, use for erections, daily use, or use for weight loss.