PT-141 Human Studies: From Nasal Spray to Phase 3 Trials
Hormonal, Growth Hormone & Body Composition Research
PT-141, also called bremelanotide, has been studied in 3,500 people across 43 completed studies, from the first nasal spray trials in men and women to two 2019 phase 3 trials in more than 1,200 women. Here are the PT-141 human studies in order and what they found. How the peptide grew out of melanotan II is covered in Melanotan II: the clinical history and the PT-141 connection; this article is about the trial results.
View product →Findings
- Two 2019 phase 3 trials in Obstetrics & Gynecology randomised 1,267 premenopausal women with low sexual desire. Over 24 weeks, PT-141 raised desire scores and lowered distress about low desire compared with placebo (pooled P<.001 for both).
- The gains held through a 52-week open-label extension that 684 women entered, with no new safety signals.
- The early trials mostly used a nasal spray. In 2006, 18 premenopausal women given a single nasal dose more often reported moderate or high desire than after placebo (P = 0.0114).
- In men, nasal PT-141 produced erectile responses beyond placebo (2004), and with low-dose sildenafil, beyond sildenafil alone in 19 men (2005).
How PT-141 human studies began: a nasal spray
The first human results, summarised in 2003, showed a rapid, dose-dependent rise in erectile activity after PT-141 in healthy men and in men with erectile dysfunction (ED) (Molinoff et al., Ann N Y Acad Sci). Most of the trial papers that followed, from 2004 to 2006, gave it as a nasal spray. A 2007 review described bremelanotide as a nasally given peptide and the only melanocortin agent then studied clinically in both men and women (Shadiack et al., Curr Top Med Chem).
| Study | People | Route |
|---|---|---|
| Int J Impot Res, 2004 | Healthy men; men with ED | Nasal spray |
| Int J Impot Res, 2004 | Healthy men; men with ED | Injection |
| Urology, 2005 | 19 men with ED | Nasal spray |
| J Sex Med, 2006 | 18 women | Nasal spray |
| Womens Health, 2016 | 327 women analysed | Injection |
| Clin Ther, 2017 | 24 healthy adults | Nasal spray |
| Obstet Gynecol, 2019 | 1,267 women | Injection |
Men, 2004. Two double-blind, placebo-controlled studies tested intranasal PT-141 in healthy men and in men with mild-to-moderate ED. In healthy men it reached peak blood levels at a median of 30 minutes and had a half-life of 1.85 to 2.09 hours. In both studies, the erectile response at the higher doses tested was statistically significant against placebo, with the first erection at about 30 minutes. It was well tolerated, and no maximum tolerated dose was found (Diamond et al., Int J Impot Res).
An injectable form was tested in men the same year. Given under the skin, PT-141 produced statistically significant erectile responses in healthy men and in men who reported adequate erections half the time or less on sildenafil, and it was well tolerated (Rosen et al., Int J Impot Res, 2004).
Men, 2005. Nineteen men with ED received low doses of nasal PT-141 plus low-dose sildenafil, sildenafil alone, or placebo, in random order. The combination produced a significantly greater erectile response than sildenafil alone, with no new or more frequent side effects (Diamond et al., Urology).
Women, 2006. Eighteen premenopausal women with female sexual arousal disorder each received a single nasal dose of bremelanotide and a placebo, in random order. More women reported moderate or high sexual desire after bremelanotide (P = 0.0114), and among those who attempted intercourse within 24 hours, significantly more were satisfied with their level of arousal (P = 0.0256), while a lab measure of genital blood flow did not change significantly (Diamond et al., J Sex Med).
The nasal form stayed in view for years. A 2011 urology review named nasal bremelanotide among the likeliest centrally acting candidates for approval in ED (Kumar and Nehra, Urol Clin North Am). In a 2017 phase 1 study of 24 healthy adults (12 men, 12 women), single nasal doses taken with or without alcohol were safe and generally well tolerated, with no clinically significant pharmacokinetic interaction and no significant drop in blood pressure. The authors noted that the nasal dose gave exposure about one to two times that of the injected dose then in phase 3 trials (Clayton et al., Clin Ther).
The large trials in women used an injection under the skin, and that is the form approved in the United States in 2019, as a self-administered injection used on demand (Dhillon and Keam, Drugs).
The injectable trials in women
A 2016 dose-finding trial in premenopausal women with sexual dysfunction let participants self-inject PT-141 or placebo as desired for 12 weeks. In the 327 women in the efficacy analysis, the two higher doses pooled raised satisfying sexual events by 0.7 a month, against 0.2 on placebo (p = 0.0180). They also lifted the Female Sexual Function Index total score by 3.6 points against 1.9 (p = 0.0017), and cut a sexual distress score by 11.1 points against 6.8 (p = 0.0014) (Clayton et al., Womens Health).
A 2019 analysis of the same trial asked how many women reached a clinically meaningful improvement. At the highest dose, responder rates beat placebo on all 7 endpoints studied (P ≤ .03), and those definitions were carried into phase 3 (Althof et al., J Sex Med).
The 2019 phase 3 trials: 1,267 women
Two identical phase 3 trials, published together in Obstetrics & Gynecology in 2019, randomised 1,267 premenopausal women with hypoactive sexual desire disorder (low sexual desire that causes distress) to PT-141 or placebo, injected under the skin as needed for 24 weeks. Their mean age was 39, and 1,202 women made up the efficacy population.
Compared with placebo, PT-141 raised the desire score by 0.30 and 0.42 points in the two trials (0.35 pooled, P<.001) and lowered distress about low desire by 0.37 and 0.29 points (0.33 pooled, P<.001). The authors described the safety profile as favourable, with nausea, flushing and headache the most common side effects, mostly mild or moderate (Kingsberg et al.).
The 52-week extension. Of 856 eligible women who finished the core trials, 684 chose to continue into a 52-week open-label extension. Women who had taken PT-141 from the start improved on the desire score by 1.25 to 1.30 points from baseline, with distress down 1.4 to 1.7 points. No new safety signals appeared, and the authors reported sustained improvement (Simon et al., Obstet Gynecol, 2019).
Across the full development program, 3,500 people took part in 43 completed studies, and some phase 3 participants used PT-141 for up to 18 months (Clayton et al., J Womens Health, 2022).
Beyond desire: appetite and body weight
PT-141 acts on the melanocortin 4 receptor, which also helps regulate appetite. Two small phase 1 trials, published in Diabetes, Obesity and Metabolism in 2022, tested it in premenopausal women with a body mass index over 30. In the first, women given PT-141 injections for 15 days lost 1.3 kg more than placebo by day 16 (p < .0001) and ate about 400 kcal a day less than placebo (p < .01). In the second, a crossover study, body weight fell 1.7 kg on twice-daily PT-141 against 0.9 kg on placebo (p < .001) (Spana et al.).
PT-141 as a nasal spray or a vial
We supply PT-141 in two formats.
PT-141 vial
A lyophilised vial, reconstituted with bacteriostatic water. The PT-141 reconstitution guide walks through it, and the peptide calculator does the arithmetic. Buy PT-141
PT-141 Nasal Spray
Pre-mixed with sterile saline in a sealed metered atomiser, in two bottle sizes: no reconstitution and no bacteriostatic water. Buy the PT-141 Nasal Spray
Our other ready-mixed sprays are listed in peptide nasal sprays. Oxytocin, the other peptide in our sexual response range, has its own human record: Oxytocin nasal spray: what human studies show. For ordering and shipping, see Buy PT-141 in Canada.
PT-141 is supplied for laboratory research use only. The trials above tested pharmaceutical bremelanotide given under medical supervision. For more, browse Hormonal, Growth Hormone and Body Composition Research.
Frequently asked questions
What has research on PT-141 shown?
In two 2019 phase 3 trials with 1,267 premenopausal women with low sexual desire, PT-141 raised desire scores and reduced distress about low desire compared with placebo over 24 weeks, and the gains were sustained through a 52-week open-label extension.
What did the first PT-141 nasal spray studies show?
Most of the early trials gave PT-141 as a nasal spray. In men it produced erectile responses beyond placebo (2004), and with low-dose sildenafil, beyond sildenafil alone (2005). In 18 premenopausal women, more reported moderate or high desire after a single nasal dose than after placebo (2006).
What has PT-141 research shown in men?
In 2004 studies, nasal and injected PT-141 produced statistically significant erectile responses against placebo in healthy men and in men with erectile dysfunction, including men who reported adequate erections half the time or less on sildenafil. In 2005, low-dose nasal PT-141 with low-dose sildenafil outperformed sildenafil alone.
What did the long-term PT-141 study show?
Of the women who finished the phase 3 trials, 684 continued into a 52-week open-label extension. Those on PT-141 from the start improved on desire by 1.25 to 1.30 points from baseline and on distress by 1.4 to 1.7 points, with no new safety signals.
Where can I buy PT-141 in Canada?
Vistara Labs supplies PT-141 as a lyophilised vial and as a ready-mixed nasal spray in sterile saline, shipped from within Canada. Laboratory research use only.
Product details from vistaralabs.ca, October 2026. Sources: Molinoff PB et al. PT-141: a melanocortin agonist for the treatment of sexual dysfunction. Ann N Y Acad Sci. 2003. PMID 12851303. Shadiack AM et al. Melanocortins in the treatment of male and female sexual dysfunction. Curr Top Med Chem. 2007. PMID 17584134. Diamond LE et al. Double-blind, placebo-controlled evaluation of the safety, pharmacokinetic properties and pharmacodynamic effects of intranasal PT-141, a melanocortin receptor agonist, in healthy males and patients with mild-to-moderate erectile dysfunction. Int J Impot Res. 2004. PMID 14963471. Rosen RC et al. Int J Impot Res. 2004. PMID 14999221. Diamond LE et al. Co-administration of low doses of intranasal PT-141, a melanocortin receptor agonist, and sildenafil to men with erectile dysfunction results in an enhanced erectile response. Urology. 2005. PMID 15833522. Diamond LE et al. An effect on the subjective sexual response in premenopausal women with sexual arousal disorder by bremelanotide (PT-141), a melanocortin receptor agonist. J Sex Med. 2006. PMID 16839319. Kumar R, Nehra A. Central nervous system agents and erectile dysfunction. Urol Clin North Am. 2011. PMID 21621083. Clayton AH et al. Phase I randomized placebo-controlled, double-blind study of the safety and tolerability of bremelanotide coadministered with ethanol in healthy male and female participants. Clin Ther. 2017. PMID 28189361. Dhillon S, Keam SJ. Bremelanotide: first approval. Drugs. 2019. PMID 31429064. Clayton AH et al. Bremelanotide for female sexual dysfunctions in premenopausal women: a randomized, placebo-controlled dose-finding trial. Womens Health (Lond). 2016. PMID 27181790. Althof S et al. Responder analyses from a phase 2b dose-ranging study of bremelanotide. J Sex Med. 2019. PMID 31277966. Kingsberg SA et al. Bremelanotide for the treatment of hypoactive sexual desire disorder: two randomized phase 3 trials. Obstet Gynecol. 2019. PMID 31599840. Simon JA et al. Long-term safety and efficacy of bremelanotide for hypoactive sexual desire disorder. Obstet Gynecol. 2019. PMID 31599847. Clayton AH et al. Safety profile of bremelanotide across the clinical development program. J Womens Health (Larchmt). 2022. PMID 35147466. Spana C et al. Effect of bremelanotide on body weight of obese women: data from two phase 1 randomized controlled trials. Diabetes Obes Metab. 2022. PMID 35170192.
