A PT-141 nasal spray is not a modern convenience. It is the original formulation, tested for years and then abandoned. The company said why, in writing, and the reason was blood pressure.
No approved PT-141 nasal spray exists, and the reason is not oversight. The spray was the original formulation, tested in 1,020 men with erectile dysfunction and then dropped. Company filings blame blood pressure, driven by uneven uptake through the nose, and the approved product is instead a 1.75 mg injection.
The nasal spray came first
Read a supplier page and intranasal PT-141 sounds like a needle-free upgrade on the injection. The development record runs the other way. In its 2007 annual report, Palatin Technologies described bremelanotide as “our nasally administered MC-based peptide in clinical development” for both male erectile dysfunction and female sexual dysfunction. The spray was the product.
The clinical trials are in the literature under both names, and they were substantial:
- 2004, healthy men and mild-to-moderate ED. Intranasal PT-141 produced a statistically significant erectile response at doses above 7 mg, with first erection at roughly 30 minutes, a median time to peak plasma level of 0.5 hours and a half-life of 1.85 to 2.09 hours.
- 2006, female sexual arousal disorder. Eighteen premenopausal women received a single intranasal dose of 20 mg in a crossover design; more reported moderate or high desire on drug than on placebo.
- 2008, sildenafil non-responders. A randomized trial gave 10 mg as an intranasal spray to 342 men; 33.5% had a positive clinical result versus 8.5% on placebo, with more drug-related adverse events on the active arm.
By the company's own account, the Phase 2B program in erectile dysfunction ran in 726 non-diabetic and 294 diabetic patients, and reported that over 30% of them were restored to a normal level of function. That is a larger and better-documented body of nasal-route evidence than exists for any other peptide sold as a spray.
Why the route was dropped
Melanocortin-4 receptor agonists raise blood pressure. That is on-target pharmacology, not an impurity problem, and it is the constraint the entire bremelanotide program was built around.
Palatin's 2007 filing records the moment the intranasal program stalled. The company had delayed the start of Phase 3 in erectile dysfunction after responses from the FDA in late August 2007 “raising serious concerns about the acceptable benefit/risk ratio to support progression into Phase 3 as a first-line therapy in the general population,” with the agency “citing blood pressure increases as its greatest safety concern.”
Two years later the company set out the conclusion, and the mechanism it blamed:
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. We believe that increases in blood pressure, as well as the rate of nausea and emesis, were due, at least partially, to variability in drug uptake with nasal administration.
Palatin Technologies, Form 10-K, 2009This is the part that transfers to every nasal peptide, not just this one. The problem was not the molecule. It was that a spray delivers an unpredictable fraction of the dose, and the patients who absorbed most were the patients whose blood pressure rose most.
Note the precise history, because it is often told wrong: the intranasal Phase 3 in erectile dysfunction did not fail. It never started.
PT-141
The same cyclic heptapeptide studied across the intranasal and subcutaneous trials cited here, supplied as lyophilized powder with a certificate of analysis matched to the lot.
What switching to injection fixed
Palatin's stated case for the subcutaneous switch was not that injection is more potent. It was that injection is predictable. In a repeat-dose Phase 1 study, the company reported that with subcutaneous administration “variability in plasma exposure was significantly decreased,” and treated that as support for its hypothesis that the nasal blood-pressure signal came from uneven uptake.
The subcutaneous form still raises blood pressure; it raises it in a way you can predict. A dedicated ambulatory monitoring study in 397 premenopausal women found systolic increases over placebo of 3.1 to 3.2 mmHg at the 1.75 mg dose in the first four hours, with peak increases typically lasting under 15 minutes and heart rate falling by about 4.6 beats per minute. Even so, 26 participants were withdrawn after randomization for pre-specified blood-pressure rises.
Melanocortin receptor agonists binding to melanocortin receptor 4 may elevate blood pressure.
White et al., Journal of Hypertension, 2017Vyleesi, approved in 2019, is the end of that line: a single-use 1.75 mg subcutaneous autoinjector, with a label that warns against use in uncontrolled hypertension or known cardiovascular disease. The device is not a lifestyle choice. It is the dose-control mechanism.
The dose arithmetic nobody quotes
The clearest published statement of what the nasal route costs comes from a Phase 1 safety study that used it. Describing its own protocol, the study notes that the intranasal 20 mg dose “has an exposure equivalent to ~1 to 2 times the subcutaneous dose currently being evaluated in Phase III studies” — that is, 1.75 mg.
Put the two numbers side by side. It took roughly 11 times the milligrams by nose to reach at most twice the exposure achieved by injection. That ratio is the pharmacokinetic fact underneath the whole story, and it is why the nasal doses in the trials above run at 7, 10 and 20 mg while the approved injection runs at 1.75 mg.
A nasal spray that claims the same dose as an injection is claiming something the development data contradicts. Same milligrams by a different route is not the same exposure, and for this compound the gap is roughly an order of magnitude.
What a grey-market nasal spray actually is
There is no approved intranasal bremelanotide product anywhere. What is sold as a PT-141 nasal spray is either research-use powder reconstituted by the buyer into a spray bottle, or a compounded preparation. Neither has published pharmacokinetics, and the one thing the original program established is that nasal uptake of this peptide varies between people.
- No delivered-dose control. The Phase 2 trials used a metered device delivering a single spray in one nostril. A reconstituted vial and a generic atomizer reproduce neither the concentration nor the plume.
- The known adverse events do not go away. Across the approved program, nausea occurred in 40% of recipients versus 1.3% on placebo, and flushing in 20.3%.
- Identity is not guaranteed. Analytical work on black-market products has characterized both bremelanotide and melanotan II in material sold to consumers.
- The efficacy base is contested anyway. Independent re-analyses of the Phase 3 program found that 72.7% of pre-specified outcomes went unreported and put the effect sizes from nil to small.
Our read: the nasal format is being sold on the appeal of avoiding a needle, and the needle is the part of this product that was engineered on purpose.
How to weigh the route question
Route-of-administration claims are usually presented as preferences. For bremelanotide there is an actual answer, and it was arrived at expensively, over roughly a decade, by the company that owned the molecule.
The mechanism argument for the compound is unchanged by any of this. Bremelanotide acts on melanocortin receptors in the central nervous system rather than on the vasculature, which is what distinguishes it from PDE5 inhibitors, and that mechanism is the same whichever way the peptide enters the body. What changes with route is how much enters, how fast, and how consistently — and for a drug whose main safety signal is a pressor effect, consistency is the safety feature.
If a supplier's nasal spray were pharmacologically equivalent to the approved injection, the equivalence would be documented somewhere. It is not documented anywhere, and the only organization that ever ran the comparison concluded against the spray.
PT-141
Research-use-only material, sold by the vial with batch documentation. Check the certificate of analysis against the batch you receive.
What to know now
- Intranasal was the original route, not a later convenience. Palatin described bremelanotide as a nasally administered peptide in its 2007 annual report.
- The nasal program reached Phase 2B in 1,020 men with erectile dysfunction and reported over 30% restored to normal function.
- It was discontinued over blood-pressure rises that the company attributed to variability in nasal uptake. The Phase 3 in men never started.
- The approved product is a 1.75 mg subcutaneous autoinjector, chosen because it controls exposure rather than because injection works better.
- A published Phase 1 study puts 20 mg intranasal at roughly one to two times the exposure of 1.75 mg subcutaneous — about eleven times the dose for at most twice the effect.
What we're watching
Two things would change this page. First, any registered trial of an intranasal melanocortin agonist with modern delivery technology, since the 2007 decision was made about a 2000s-era spray device and the problem it identified was engineering rather than chemistry. Second, post-marketing blood-pressure data on the approved injection, which would tell us how much of the pressor signal survives outside a trial population screened for cardiovascular risk. We are also watching whether any compounded nasal preparation is ever characterized in a published pharmacokinetic study, because at present none has been.
Frequently asked questions
Is there an approved PT-141 nasal spray?
No. No regulator has approved an intranasal bremelanotide product. The only approved form is Vyleesi, a 1.75 mg subcutaneous autoinjector, cleared in the United States in 2019 for premenopausal women with acquired, generalized hypoactive sexual desire disorder.
Why was the PT-141 nasal spray discontinued?
Blood pressure. Palatin's annual reports state that increases in blood pressure in patients receiving nasally administered bremelanotide were a significant factor in discontinuing that route, and attribute them partly to variability in how much drug each patient absorbed through the nose.
Does a nasal spray need a bigger dose than an injection?
For this compound, yes. A Phase 1 study reported that 20 mg intranasally produced roughly one to two times the exposure of the 1.75 mg subcutaneous dose then in Phase 3 — about eleven times the milligrams for at most double the exposure.
Did the intranasal trials show any effect?
They did. Intranasal dosing produced statistically significant erectile responses above 7 mg in 2004, and a 342-man trial in 2008 reported 33.5% positive clinical results versus 8.5% on placebo. Efficacy was never the stated reason for dropping the route.
References
- Palatin Technologies, Inc. (2007). Annual report on Form 10-K for the fiscal year ended June 30, 2007. U.S. Securities and Exchange Commission. https://www.sec.gov/Archives/edgar/data/911216/000108802007000042/form10k_063007.htm
- Palatin Technologies, Inc. (2009). Annual report on Form 10-K for the fiscal year ended June 30, 2009. U.S. Securities and Exchange Commission. https://www.sec.gov/Archives/edgar/data/911216/000108802009000050/form10k_063009.htm
- Diamond, L. E., Earle, D. C., Rosen, R. C., Willett, M. S., & Molinoff, P. B. (2004). 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. International Journal of Impotence Research, 16(1), 51-59. https://doi.org/10.1038/sj.ijir.3901139
- Diamond, L. E., Earle, D. C., Heiman, J. R., Rosen, R. C., Perelman, M. A., & Harning, R. (2006). An effect on the subjective sexual response in premenopausal women with sexual arousal disorder by bremelanotide (PT-141), a melanocortin receptor agonist. Journal of Sexual Medicine, 3(4), 628-638. https://doi.org/10.1111/j.1743-6109.2006.00268.x
- Safarinejad, M. R., & Hosseini, S. Y. (2008). Salvage of sildenafil failures with bremelanotide: A randomized, double-blind, placebo controlled study. Journal of Urology, 179(3), 1066-1071. https://doi.org/10.1016/j.juro.2007.10.063
- Clayton, A. H., Lucas, J., DeRogatis, L. R., & Jordan, R. (2017). Phase I randomized placebo-controlled, double-blind study of the safety and tolerability of bremelanotide coadministered with ethanol in healthy male and female participants. Clinical Therapeutics, 39(3), 514-526.e14. https://doi.org/10.1016/j.clinthera.2017.01.018
- White, W. B., Myers, M. G., Jordan, R., & Lucas, J. (2017). Usefulness of ambulatory blood pressure monitoring to assess the melanocortin receptor agonist bremelanotide. Journal of Hypertension, 35(4), 761-768. https://doi.org/10.1097/hjh.0000000000001221
- U.S. Food and Drug Administration. (2019). Vyleesi (bremelanotide injection) prescribing information. https://www.accessdata.fda.gov/drugsatfda_docs/label/2019/210557s000lbl.pdf
- Clayton, A. H., Kingsberg, S. A., Portman, D., et al. (2022). Safety profile of bremelanotide across the clinical development program. Journal of Women's Health, 31(2), 171–182. https://doi.org/10.1089/jwh.2021.0191
- Simon, J. A., Kingsberg, S. A., Portman, D., et al. (2022). Prespecified and integrated subgroup analyses from the RECONNECT phase 3 studies of bremelanotide. Journal of Women's Health, 31(3), 391–400. https://doi.org/10.1089/jwh.2021.0225
- Spielmans, G. I. (2021). Re-analyzing phase III bremelanotide trials for "hypoactive sexual desire disorder" in women. Journal of Sex Research, 58(9), 1085–1105. https://doi.org/10.1080/00224499.2021.1885601
- Pfaus, J. G., Sadiq, A., Spana, C., & Clayton, A. H. (2022). The neurobiology of bremelanotide for the treatment of hypoactive sexual desire disorder in premenopausal women. CNS Spectrums, 27(3), 281–289. https://doi.org/10.1017/S109285292100002X
- Mestria, S., Odoardi, S., Frison, G., & Strano Rossi, S. (2021). LC-HRMS characterization of melanotan II and bremelanotide sold on the black market. Drug Testing and Analysis, 13(4), 876–882. https://doi.org/10.1002/dta.2986
- Cipriani, S., Alfaroli, C., Maseroli, E., & Vignozzi, L. (2023). An evaluation of bremelanotide injection for the treatment of hypoactive sexual desire disorder. Expert Opinion on Pharmacotherapy, 24(1), 15–21. https://doi.org/10.1080/14656566.2022.2132144