PT-141

PT-141 (bremelanotide) is a cyclic heptapeptide melanocortin receptor agonist approved by the FDA in 2019 under the brand name Vyleesi for the treatment of hypoactive sexual desire disorder (HSDD) in premenopausal women. PT-141 was derived from Melanotan 2 (MT-2) research at the University of Arizona and differs from MT-2 by having a free carboxylic acid C-terminus instead of an amide. This modification shifts its pharmacological profile toward greater MC4R-mediated effects. PT-141 is the first FDA-approved melanocortin-based therapy for sexual dysfunction and represents a novel mechanism of action distinct from phosphodiesterase inhibitors (like sildenafil) or hormonal therapies. Its mechanism involves central nervous system activation of melanocortin-4 receptors in brain regions controlling sexual arousal, rather than peripheral vascular effects.

PT-141 has been investigated for its agonist activity at melanocortin-4 receptors (MC4R) in the central nervous system. Researchers observed that MC4R activation in the paraventricular nucleus of the hypothalamus triggers oxytocinergic neuron firing, with oxytocin projections to spinal cord autonomic centers controlling genital arousal responses. Studies suggest that this central mechanism is fundamentally different from PDE5 inhibitors, which act peripherally on vascular smooth muscle. In clinical trials, researchers observed that PT-141 produced measurable changes in sexual desire and arousal scores that were not accompanied by direct peripheral vascular effects, confirming its CNS-mediated mechanism. PT-141 also activates MC1R (with lower affinity than MC4R), which can produce transient skin flushing. The compound acts on arousal pathways upstream of genital vascular responses, modulating the neural circuits that initiate sexual motivation rather than the peripheral effector mechanisms.

FDA Approval Studies

Kingsberg et al. (2019) reported results from the RECONNECT Phase 3 trials that led to FDA approval. Researchers observed statistically significant improvements in sexual desire scores and reductions in distress associated with low sexual desire in premenopausal women [1].

MC4R Mechanism

Pfaus et al. (2007) investigated bremelanotide’s mechanism and demonstrated that its sexual function effects were mediated through central MC4R activation and oxytocinergic pathway signaling, distinct from peripheral vascular mechanisms [2].

Development from MT-2

Molinoff et al. (2003) described the development of bremelanotide from the MT-2 scaffold and its characterization as a melanocortin receptor agonist for sexual dysfunction research [3].