Melanotan II vs PT-141 (Bremelanotide): Melanocortin Receptor Selectivity

Melanotan II (MT-II) is a synthetic cyclic heptapeptide analog of α-MSH that acts as a non-selective agonist across MC1R, MC3R, MC4R, and MC5R. PT-141 (bremelanotide) is a metabolite of MT-II that lacks the C-terminal amide and shows altered receptor-selectivity.

In binding studies, MT-II shows comparable nanomolar affinity across the four melanocortin receptor subtypes. PT-141 retains MC3R/MC4R agonism but with reduced MC1R activity — which is the molecular basis for its distinct pharmacological profile in research models.

For researchers comparing the two: cAMP-accumulation assays in HEK293 cells stably expressing individual MCR subtypes are the standard. Expect EC50 values in the low-nM range for both peptides at MC4R; MT-II will show comparable potency at MC1R while PT-141 will not.

Storage: lyophilized at -20°C. Both peptides are stable in solution at 2–8°C for several weeks. For research use only.