PT-141, also known as bremelanotide, is a synthetic cyclic heptapeptide derived from Melanotan II by removal of the C-terminal amide group. It acts as a non-selective melanocortin receptor agonist, with primary affinity for MC3R and MC4R in the central nervous system — the melanocortin receptors most implicated in sexual motivation, arousal, and reward pathways.
Unlike phosphodiesterase-5 (PDE5) inhibitors such as sildenafil, which act peripherally via vascular smooth muscle relaxation, PT-141 operates centrally through hypothalamic and limbic melanocortin signalling. MC4R activation in the medial preoptic area (mPOA) and the paraventricular nucleus (PVN) modulates dopaminergic tone, oxytocin release, and nitric oxide synthesis — producing pro-erectile and pro-libido effects through pathways independent of the nitric oxide–cGMP cascade.
A subcutaneous formulation of bremelanotide (Vyleesi®) was approved by the FDA in June 2019 for hypoactive sexual desire disorder (HSDD) in premenopausal women — the first melanocortin-based drug to reach approval. Research with the peptide continues across male erectile function, female arousal disorders, and central melanocortin signalling biology.
Research Applications
MC3R/MC4R Agonism
PT-141 demonstrates high-affinity binding at MC3R (Ki ~0.4 nM) and MC4R (Ki ~1.0 nM), with weaker activity at MC1R and MC5R. Central MC4R activation drives the primary pro-sexual effects; MC3R engagement modulates energy homeostasis and may mediate some of the observed nausea side effects at higher doses.
Male Erectile Function
Subcutaneous PT-141 produces dose-dependent erectile responses in preclinical models via central MC4R activation in the mPOA, independent of PDE5 inhibition. Phase II trials (Diamond et al., 2004; J Sex Med) demonstrated significant improvement in erectile function scores versus placebo, including in men non-responsive to sildenafil.
Female Sexual Arousal Disorder (FSAD) & HSDD
The FDA-approved Vyleesi® formulation (1.75 mg SC) demonstrated statistically significant improvement in desire and distress scores in two Phase III trials (RECONNECT studies, Obstet Gynecol 2019). Mechanistically, MC4R in the mPOA modulates dopamine release in the nucleus accumbens, increasing motivational salience for sexual stimuli.
Central Melanocortin System Research
PT-141 is used as a pharmacological tool to probe melanocortin circuitry — particularly the MC4R-oxytocin pathway. Rodent studies demonstrate that MC4R-expressing PVN neurons project to autonomic preganglionic neurons and release oxytocin, providing a mechanistic link between central melanocortin signalling and peripheral genital response.
Neuropeptide Interaction Studies
Research models use PT-141 to study interactions between the melanocortin system and endocannabinoid, serotonergic, and opioid pathways. MC4R knockout studies have established its role in satiety, reward, and autonomic regulation beyond sexual function — making PT-141 a useful probe for broader neuroendocrine research.
Notes: Confirm CNS-dependent vs peripheral mechanism
Receptor Selectivity
Dose: 10 nM–1 µM binding assay
Endpoint: Ki at MC1R, MC3R, MC4R, MC5R
Notes: Radioligand displacement; compare bremelanotide vs MT-II vs afamelanotide
Oxytocin Pathway
Dose: 0.5 mg/kg SC + OXT antagonist pre-treatment
Endpoint: PVN oxytocin neuron activation
Notes: Atosiban or L-368,899 pre-treatment to block OXT receptor
Peptide Research Tools — Use our free peptide calculator for reconstitution, BAC water, dosing, half-life, and mixing charts.
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Frequently Asked Questions
What is PT-141 (bremelanotide)?
PT-141 is a synthetic cyclic heptapeptide melanocortin receptor agonist derived from Melanotan II. It selectively activates MC3R and MC4R in the central nervous system, modulating hypothalamic pathways involved in sexual motivation and arousal. A pharmaceutical-grade formulation (Vyleesi®) is FDA-approved for HSDD in premenopausal women.
How does PT-141 differ from PDE5 inhibitors like sildenafil?
PDE5 inhibitors act peripherally by preventing breakdown of cGMP in vascular smooth muscle, increasing blood flow. PT-141 acts centrally via MC3R/MC4R in the mPOA and PVN — triggering dopaminergic and oxytocinergic signalling independent of the nitric oxide pathway. This is why PT-141 can produce responses in patients non-responsive to PDE5 inhibitors.
What receptors does PT-141 bind?
PT-141 binds all five melanocortin receptors but with primary affinity for MC3R (Ki ~0.4 nM) and MC4R (Ki ~1.0 nM). MC1R (Ki ~3.6 nM) and MC5R (Ki ~5.4 nM) are lower-affinity targets. MC4R in the medial preoptic area drives the primary pro-sexual and erectile effects observed in research models.
Is PT-141 the same as Melanotan II?
No. PT-141 is derived from Melanotan II by removal of the C-terminal amide group, producing a less lipophilic analogue with reduced tanning activity but retained MC3R/MC4R pro-sexual efficacy. MT-II retains stronger MC1R activity (responsible for melanogenesis), while PT-141’s profile is better suited for CNS-focused melanocortin research.
What is the QSC PT-141 purity specification?
QSC PT-141 is manufactured via in-house solid-phase peptide synthesis (SPPS) at our Qingdao facility. Every batch is tested to ≥99% purity by HPLC and identity-confirmed by mass spectrometry (MS). Janoshik COAs are available on the product page for independent third-party verification.
