SHU 9119 is a potent human melanocortin 3 and 4 receptors (MC3/4R) antagonist and a partial MC5R agonist; with IC₅₀ values of 0.23, 0.06, and 0.09 nM for human MC3R, MC4R and MC5R, respectively. IC50 & Target: IC50: 0.23 nM (MC3R); 0.23 nM (MC4R); 0.23 nM (MC5R)^[1] In Vivo: Blockade of CNS-Mcr via chronic intracerebroventricular infusion of SHU9119 (24 nmol/d for 7 days) increases food intake in ad libitum-fed rats compared with control. Weight gain of SHU9119 treated rats is significantly higher than control. SHU9119 treatment potently increases metabolic efficiency. SHU9119 markedly increases mRNA levels of genes promoting lipogenesis and TAG storage in adipocytes, including stearoyl-CoA desaturase-1, lipoprotein lipase, acetyl-CoA carboxylase α, and fatty acid synthase^[2]. SHU9119 increases food intake (+30%) and body fat (+50%) and decreases EE by reduction in fat oxidation (−42%). In addition, SHU9119 impairs the uptake of VLDL-TG by BAT. In line with this, SHU9119 decreases uncoupling protein-1 levels in BAT (−60%) and induces large intracellular lipid droplets, indicative of severely disturbed BAT activity^[3].