Key Statistics
| Statistic | Value | Detail |
|---|---|---|
| Regulatory Status | FDA Approved | June 21, 2019 as Vyleesi |
| Phase 3 Trials | 1,247 | Patients in RECONNECT studies |
| Desire Score | 0.35 | FSFI-D increase vs placebo |
| Mechanism | MC4R | Melanocortin receptor activation |
| Subjects Studied | 3,500+ | Across 43 clinical trials |
Mechanism of Action
Central Nervous System Action
PT-141 (Bremelanotide) is a synthetic cyclic heptapeptide that activates melanocortin receptors MC3R and MC4R in the central nervous system. Unlike PDE5 inhibitors (Viagra, Cialis) that work on blood flow, PT-141 works directly on the brain pathways involved in sexual desire and arousal. It is an active metabolite of Melanotan II, differing only by lacking the C-terminal amide group.
Biological Pathways
MC4R Pathway (Primary)
Melanocortin Receptor Type 4
- Activates sexual arousal pathways in hypothalamus
- Increases sexual desire and motivation
- Modulates dopaminergic signaling
MC3R Pathway (Moderate)
Melanocortin Receptor Type 3
- Contributes to sexual response
- Involved in energy homeostasis
- Modulates limbic system activity
Nitric Oxide (Moderate)
Nitric Oxide Release
- Supports physiological arousal
- Complements central action
Key Mechanism
Brain-Based Action
PT-141 works differently from erectile dysfunction drugs. It activates melanocortin receptors in the hypothalamus to enhance sexual desire at its source — the brain — rather than just improving blood flow.
Source: FDA Approval Data
| Metric | Value |
|---|---|
| MC4R Activation | ✓ Strong |
| Sexual Function | ✓ Primary effect |
| Melanogenesis | ↓ Reduced |
| Appetite Effects | ↓ Minimal |
Clinical Findings
| Metric | Value | Context |
|---|---|---|
| FSFI-D Score Improvement | +0.35 | Phase 3 RECONNECT trials integrated |
| Statistical Significance | P<.001 | For desire improvement |
| Distress Reduction | P<.005 | For distress related to low desire |
Trial details: Participants received bremelanotide 1.75 mg subcutaneously as needed for 24 weeks. Both studies showed statistically significant improvements in sexual desire and reductions in distress.
Preclinical Effects
| Effect | Model | Value |
|---|---|---|
| Erection Quality | Male ED studies | +75% |
| Sexual Satisfaction | Clinical trials | +70% |
| Desire Enhancement | RECONNECT trials | +80% |
| Onset of Action | Rapid effect | 45-60 min |
Research Areas
Sexual Desire — Enhancement of Desire
PT-141 significantly improves sexual desire by activating melanocortin receptors in the hypothalamus, addressing the neurological basis of low libido.
Source: RECONNECT Phase 3 Trials
Male Sexual Function — Erectile Function Research
PT-141 has been studied for male erectile dysfunction, including in men who did not respond to PDE5 inhibitors, offering an alternative mechanism.
Source: Int J Impotence Research 2004
CNS Mechanism — Unique Mechanism
PT-141 is the first FDA-approved drug for HSDD that works through the central nervous system via melanocortin receptors, rather than through peripheral mechanisms.
Dosing Flexibility — As-Needed Use
Not a daily medication. Use when desired, offering dosing flexibility compared to daily treatments.
Dosing Protocols
FDA-Approved Protocol (Vyleesi)
Dose: 1.75 mg | Frequency: As needed, ≥45 min before activity | Duration: Max 8 doses/month
- Approved for premenopausal women with HSDD
- Self-administered subcutaneous injection
- Maximum one dose per 24 hours
- 24-week core treatment period in trials
Male ED Research Protocol
Dose: 1-2 mg | Frequency: As needed, subcutaneous or intranasal | Duration: Research protocols varied
- Various doses studied (0.5-10 mg)
- Intranasal route also studied
- Dose-response relationship established
- Not FDA-approved for men
Pharmacokinetics
| Parameter | Value |
|---|---|
| Half-Life | ~2.7 hours |
| Peak Concentration | ~2 hours (peak effect) |
| Bioavailability | Subcutaneous injection |
| Stability | Protect from light |
| Excretion | Metabolized to inactive fragments |
| Metabolism | Onset 45-60 min, duration up to 24 hours |
Safety Profile
| Issue | Incidence | Severity |
|---|---|---|
| Nausea | 40% | mild |
| Flushing | 20% | mild |
| Injection Site Reactions | 13% | mild |
| Headache | 11% | mild |
- FDA-approved with well-characterized safety profile
- 3,500 subjects studied across 43 clinical trials
- Most side effects are mild and transient
- Nausea can be reduced by taking on empty stomach
Compound Information
| Property | Value |
|---|---|
| Type | Cyclic heptapeptide |
| CAS Number | 189691-06-3 |
| Molecular Weight | 1025.2 g/mol |
| Amino Acids | 7 residues |
| Sequence | Ac-Nle-c[Asp-His-D-Phe-Arg-Trp-Lys]-OH |
| Formula | C50H68N14O10 |
Frequently Asked Questions
Q: What is PT-141 and how is it related to Melanotan II?
A: PT-141 (Bremelanotide) is a cyclic heptapeptide that is the active metabolite of Melanotan II (MT-II). When the body processes Melanotan II, it removes the C-terminal amide group to create PT-141. This modification focuses the peptide’s activity on melanocortin receptors MC3R and MC4R involved in sexual function, while reducing the tanning (melanogenesis) effects associated with MT-II. PT-141 is FDA-approved as Vyleesi for treating hypoactive sexual desire disorder in premenopausal women.
Q: How does PT-141 differ from Viagra or Cialis?
A: PT-141 works through a completely different mechanism than PDE5 inhibitors like Viagra (sildenafil) or Cialis (tadalafil). While PDE5 inhibitors work on blood vessels to improve erection by enhancing blood flow, PT-141 works in the central nervous system by activating melanocortin receptors in the hypothalamus to enhance sexual desire itself. This makes PT-141 a potential option for individuals who don’t respond to PDE5 inhibitors.
Q: What did the clinical trials show?
A: Two identical Phase 3 trials (RECONNECT) enrolled 1,247 premenopausal women with hypoactive sexual desire disorder. Women received bremelanotide 1.75 mg subcutaneously as needed for 24 weeks. Both studies showed statistically significant improvements in sexual desire (FSFI-D: +0.30 to +0.42 points, P<.001) and significant reductions in distress (FSDS-DAO: -0.29 to -0.37 points, P<.005) compared to placebo.
Q: Is PT-141 approved for use in men?
A: PT-141 is FDA-approved only for premenopausal women with HSDD (as Vyleesi). It is not approved for use in men. However, it has been studied in men with erectile dysfunction, including those who did not respond to PDE5 inhibitors, and showed efficacy through its CNS mechanism. For men, PT-141 remains a research compound.
Q: How is PT-141 administered?
A: PT-141 is administered as a subcutaneous injection at least 45 minutes before anticipated sexual activity. The FDA-approved dose is 1.75 mg, with a maximum of one dose per 24 hours and no more than 8 doses per month recommended.
Q: What are the main side effects?
A: The most common side effects in clinical trials were nausea (40%), flushing (20%), injection site reactions (13%), and headache (11%). Most adverse events were mild to moderate. PT-141 may also cause temporary increases in blood pressure and focal hyperpigmentation (skin darkening) that may not fully resolve.
References
- Kingsberg SA, Clayton AH, Portman D, et al. (2019) “Bremelanotide for the Treatment of Hypoactive Sexual Desire Disorder: Two Randomized Phase 3 Trials” Obstetrics & Gynecology DOI: 10.1097/AOG.0000000000003500 PMID: 31599840
- Diamond LE, Earle DC, Rosen RC, et al. (2004) “PT-141: a melanocortin agonist for the treatment of sexual dysfunction” International Journal of Impotence Research PMID: 12851303
- Diamond LE, Earle DC, Heiman JR, et al. (2006) “An effect on the subjective sexual response in premenopausal women with sexual arousal disorder by bremelanotide (PT-141)” Journal of Sexual Medicine DOI: 10.1111/j.1743-6109.2006.00268.x PMID: 16839319
- Multiple authors (2022) “Safety Profile of Bremelanotide Across the Clinical Development Program” Journal of Women’s Health
- FDA (2019) “Vyleesi (bremelanotide) Prescribing Information” FDA
- Multiple authors (2022) “Bremelanotide for Treatment of Female Hypoactive Sexual Desire Disorder” Medicina (Kaunas) PMID: 35056399