SNT207858 free base is a selective, blood brain barrier penetrating, potent and orally active melanocortin-4 (MC-4) receptor antagonist. SNT207858 free base has an IC50 of 22 nM (binding) and 11 nM (function) on the MC-4 receptor.IC50 & Target: MC-4 receptorIn Vitro: SNT207858 binds to the MC-4 receptor with an affinity of 22 nM and shows a 170-fold selectivity vs. MC-3 and a 40-fold selectivity vs. MC-5.In Vivo: SNT207858 (30 mg/kg; oral administration; once daily; 15 days) significantly reduces the tumor induced weight loss in mice.