PT-141

Description

PT-141 (Bremelanotide) is a cyclic heptapeptide melanocortin receptor agonist derived from the tanning peptide Melanotan II. During Melanotan II clinical trials, researchers noted an unexpected side effect: significant increases in sexual arousal in both male and female subjects. PT-141 was subsequently developed to isolate this activity — becoming the only peptide-based compound to receive FDA approval (as Vyleesi) for a sexual health indication.

Research Profile

PT-141 works through a mechanism fundamentally different from PDE5 inhibitors. It activates melanocortin-4 receptors (MC4R) in the central nervous system — specifically in the hypothalamus and limbic system — rather than acting on peripheral vascular tissue. This CNS-mediated mechanism means PT-141 addresses desire and arousal at the neurological level, not just the vascular level. Phase III clinical data showed statistically significant increases in sexual desire scores compared to placebo.

Key Research Areas

• Melanocortin-4 receptor activation in CNS
• Sexual arousal and desire through central mechanisms
• Erectile function in PDE5 non-responder models
• Female sexual interest and arousal
• Melanocortin system signaling pathways

Specifications

Sequence	Cyclic: Ac-Nle-c[Asp-His-D-Phe-Arg-Trp-Lys]-OH
Molecular Weight	1025.18 g/mol
Purity	≥99% (HPLC verified)
Form	Lyophilized powder
Quantity	10mg per vial
Storage	-20°C pre-reconstitution

Related Research Peptides

PT-141 was derived from Melanotan II — which retains both tanning and sexual health properties. For hormonal signaling research, see Kisspeptin. Full overview at our sexual health peptides guide.

Research Dosage Protocols

PT-141 (bremelanotide) is FDA-approved as Vyleesi at 1.75mg subcutaneous injection. Research doses in clinical trials ranged from 0.3–7.5mg, with 1.75mg established as the optimal dose balancing efficacy and nausea incidence. A 10mg vial reconstituted in 5mL bacteriostatic water yields 2,000mcg/mL (2mg/mL). Timing in research protocols: administration occurs 45–120 minutes before the measurement window (observation session, partner interaction study, physiological response measurement) because MC4R-mediated arousal effects peak within this timeframe and persist 4–8 hours. The clinical approval provides unusually detailed human PK and efficacy data compared to most research peptides.

Frequently Asked Questions

How does PT-141 differ from Viagra and Cialis mechanistically?

Viagra (sildenafil) and Cialis (tadalafil) are PDE5 inhibitors — they prevent the breakdown of cGMP in penile smooth muscle, which maintains vasodilation and sustains erection once arousal is already present. They are vascular drugs: they facilitate blood flow but don’t generate arousal. PT-141 is a melanocortin-4 receptor (MC4R) agonist that works in the central nervous system — specifically hypothalamic regions involved in sexual arousal and motivation. It activates the brain’s sexual motivation circuitry, increasing desire rather than just blood flow. This CNS mechanism means PT-141 can work in settings where PDE5 inhibitors fail (female sexual dysfunction, psychogenic causes) and works even in the absence of tactile stimulation.

What is Vyleesi, and what does FDA approval mean for PT-141 research?

Vyleesi is the brand name for FDA-approved bremelanotide (PT-141), approved in June 2019 for hypoactive sexual desire disorder (HSDD) in premenopausal women. It was developed by AMAG Pharmaceuticals (later acquired by Palatin Technologies). The approval followed Phase 2 and 3 clinical trials involving several thousand women, generating detailed human safety, pharmacokinetic, and efficacy data. For research purposes, this clinical history provides a documented human dose-response profile, identified adverse event rates (primarily nausea, flushing, and transient blood pressure elevation), and PK parameters including Tmax (~60 min subcutaneous) and half-life (~2.7 hours).

Does PT-141 work in both males and females in research?

Yes — clinical trials and research have studied PT-141 in both sexes. The FDA approval is specifically for premenopausal women with HSDD, but earlier Phase 2 trials included men with erectile dysfunction who had failed PDE5 inhibitor therapy. In male research, PT-141 demonstrated significant erectile responses without requiring the vascular mechanism of PDE5 inhibitors. The MC4R receptors involved in sexual arousal are present in both male and female hypothalamic circuits. Research in animal models shows consistent effects across sexes. The sex-specific approval doesn’t reflect a biological sex limitation — it reflects that AMAG’s commercial development strategy prioritized the female HSDD indication.

How long before an observation window should PT-141 be administered?

PT-141 peaks in plasma at approximately 60 minutes after subcutaneous injection. Effects on arousal and physiological response variables typically begin within 30–45 minutes and are most prominent at the 1–2 hour mark. Research and clinical protocols consistently recommend 45–120 minutes pre-observation administration. The effect window extends 4–8 hours depending on dose. Importantly, PT-141’s MC4R-mediated effects don’t require physical stimulation to initiate — this is a key research variable when designing observation windows. The blood pressure elevation effect (typically 5–7 mmHg systolic) also peaks around the 60-minute mark, which is relevant for protocols measuring cardiovascular parameters.

How was nausea managed in clinical research studies?

Nausea was the most common adverse event in PT-141 clinical trials, occurring in ~40% of subjects at the 1.75mg dose. Clinical management strategies evaluated in the trials included antiemetic pre-treatment and dose titration approaches. Research starting at lower doses (0.5–1mg) and escalating showed reduced nausea incidence without equivalent efficacy loss at moderate doses. The nausea mechanism is MC4R activation in the area postrema (the brain’s vomiting center) — the same receptor driving the intended effects also mediates this side effect. Some researchers use ondansetron pre-treatment in protocols where nausea would compromise data collection or subject welfare in animal models.

What is PT-141’s relationship to Melanotan II?

PT-141 is a derivative of Melanotan II (MT-II). MT-II was originally developed as a tanning peptide through non-selective melanocortin receptor activation (MC1R through MC5R). During MT-II clinical trials, researchers noticed potent sexual arousal effects — these were traced to MC4R activation. PT-141 was developed by modifying MT-II to reduce melanotropic (tanning/pigmentation) activity while retaining MC4R-mediated arousal effects. The key modification: PT-141 lacks the Nle4 substitution that drives strong MC1R melanin signaling. This selective MC4R emphasis is what makes PT-141 a pharmaceutical candidate while MT-II’s non-selectivity complicated its clinical development.

How do I reconstitute PT-141 for research use?

Add 5mL bacteriostatic water to a 10mg vial for a working concentration of 2,000mcg/mL (2mg/mL). At this concentration, a 1.75mg (clinical-equivalent) dose requires 0.875mL, which is easily drawn in a standard 1mL syringe. For smaller research doses of 0.5–1mg, volumes are 0.25–0.5mL. PT-141 dissolves readily. Refrigerate at 2–8°C post-reconstitution; stable approximately 4–6 weeks. Lyophilized powder stored at -20°C retains potency for 24 months. PT-141 is not particularly light-sensitive compared to some peptides, but amber vials are still preferred for long-term storage to minimize oxidative degradation.

For research and laboratory use only. Not for human consumption. All peptides are sold strictly as research chemicals.