– MSG606 TFA, a potent antagonist of the human MC1 receptor (IC50 = 17 nM), functions as a partial agonist at the human MC3 and MC5 receptors (EC50 values of 59 and 1300 nM, respectively). It demonstrates binding affinity for A375 melanoma cells in vitro and selectively reverses induced hyperalgesia in female mice without affecting male mice.