PT-141

PT-141 (Bremelanotide) is a synthetic cyclic heptapeptide analogue of alpha-melanocyte-stimulating hormone (α-MSH) developed as a melanocortin receptor agonist. Originally derived from Melanotan II in the 1990s by Palatin Technologies, bremelanotide was specifically developed to address sexual dysfunction after the parent compound unexpectedly caused sexual arousal in clinical trials for tanning. The peptide primarily activates melanocortin receptors MC3R and MC4R in the central nervous system, particularly in the hypothalamic regions involved in sexual response. After extensive clinical development including two large Phase 3 RECONNECT trials involving over 1,200 premenopausal women, bremelanotide received FDA approval in June 2019 for the treatment of acquired, generalized hypoactive sexual desire disorder (HSDD) in premenopausal women. It is marketed as Vyleesi and administered as a 1.75 mg subcutaneous injection at least 45 minutes before anticipated sexual activity. The FDA considers it a first-in-class medication, representing a novel non-hormonal approach to treating sexual dysfunction through central melanocortin pathway activation.

Sexual Function

• Enhanced sexual desire: Clinical trials demonstrated statistically significant increases in sexual desire scores (0.35 points, P<.001) compared to placebo in premenopausal women with HSDD, with effect sizes of 0.39 for desire improvements ^[1][5]
• Reduced sexual distress: Significantly decreased distress related to low sexual desire (-0.33 points, P<.001) with an effect size of 0.27 for distress reduction ^[1][5]
• Erectile function: Early studies in men with mild-to-moderate erectile dysfunction showed statistically significant dose-dependent erectile responses at doses exceeding 7 mg, with erections occurring approximately 30 minutes post-administration ^[3]
• Sustained efficacy: Long-term data from 52-week extension studies demonstrated maintained therapeutic benefits with stable improvement scores throughout extended treatment ^[8]

Melanocortin Activation

• Central nervous system mechanism: Functions through non-selective activation of melanocortin receptors MC1R, MC3R, MC4R, and MC5R, with primary therapeutic effects mediated through MC4R in the hypothalamus ^[2][10]
• Dopaminergic modulation: Activates MC4R receptors in the medial preoptic area of the hypothalamus, potentially increasing dopamine release in brain regions associated with sexual motivation and reward ^[10]
• Non-vascular pathway: Unlike traditional erectile dysfunction medications, bremelanotide works through central melanocortin pathways rather than peripheral vascular mechanisms, offering an alternative approach for patients ^[3][4]

Clinical Safety Profile

Bremelanotide has been evaluated in over 3,500 subjects across 43 clinical studies spanning Phase 1-3 trials, with no deaths reported and a generally favorable safety profile ^[12]. The medication demonstrated acceptable tolerability in long-term studies extending up to 52 weeks, with sustained safety parameters and no new safety signals emerging during extended treatment ^[8]. A Phase I study confirmed safe coadministration with ethanol, showing no clinically significant pharmacokinetic interactions or serious adverse events ^[9].

Regulatory Status

Bremelanotide received FDA approval on June 21, 2019, for the treatment of acquired, generalized hypoactive sexual desire disorder in premenopausal women. The FDA considers it a first-in-class medication ^[2]. It is marketed as Vyleesi by AMAG Pharmaceuticals and administered as a 1.75 mg subcutaneous injection at least 45 minutes before anticipated sexual activity, with a maximum recommended frequency of once per 24 hours and no more than 8 doses per month.

Side Effects and Risks

The most common treatment-emergent adverse events include nausea (40.0% vs. 1.3% placebo), flushing (20.3% vs. 1.3% placebo), and headache (11.3% vs. 1.9% placebo) ^[12]. Other reported effects include injection site reactions (13%), vomiting (4.8%), and dizziness (2.2%) ^[5]. Most adverse events are mild to moderate in severity, though nausea was the primary reason for treatment discontinuation (8.1% of patients) ^[12]. Bremelanotide causes transient increases in systolic blood pressure (approximately 6 mmHg) and diastolic blood pressure (approximately 3 mmHg), typically lasting less than 15 minutes, warranting caution in patients with cardiovascular conditions or uncontrolled hypertension ^[12]. Focal hyperpigmentation may occur with extended consecutive dosing exceeding recommended frequency. Rare instances of clinically apparent acute liver injury have been reported, though no cases of acute liver failure or chronic liver injury have occurred ^[7].

Research Gaps

Long-term safety data beyond 52 weeks remains limited. The mechanism by which bremelanotide enhances sexual desire is not fully understood, with recent 2025 animal studies suggesting it may work through pathways other than the dopamine reward system previously hypothesized ^[6]. Additional research is needed to understand individual response variability, optimal dosing strategies, and efficacy in postmenopausal women and men with sexual dysfunction. The long-term cardiovascular effects of repeated blood pressure elevations require further investigation.