PT-141 (Bremelanotide) is a synthetic cyclic peptide analogue of α-MSH and a non-selective melanocortin receptor agonist, with activity at MC1R, MC3R, MC4R, and MC5R. Its primary research application centers on MC4R activation in the central nervous system, which has been linked to sexual arousal and motivation pathways in both male and female models. Unlike PDE5 inhibitors, PT-141 acts centrally rather than through vascular mechanisms, making it a mechanistically distinct compound for libido and sexual function research. It has been studied in models of hypoactive sexual desire and erectile dysfunction.