Melanin-concentrating hormone 1-receptor antagonist suppresses body weight gain correlated with high receptor occupancy levels in diet-induced obesity mice

Melanin-concentrating hormone (MCH), which is a neuropeptide expressed in the hypothalamus of the brain, is involved in regulating feeding behavior and energy homeostasis via the MCH1 receptor in rodents. It is widely considered that MCH1 receptor antagonists are worthy of development for medical treatment of obesity. Here we report on the development of an ex vivo receptor occupancy assay using a new radiolabeled MCH1 receptor antagonist, [35S]-compound D. An MCH1 receptor antagonist inhibited the binding of [35S]-compound D to brain slices in a dose-dependent manner. The result showed a good correlation between the receptor occupancy levels and plasma or brain levels of the MCH1 receptor antagonist, suggesting that the ex vivo receptor binding assay using this radioligand is practical. Quantitative analysis in diet-induced obese mice showed that the efficacy of body weight reduction correlated with the receptor occupancy levels at 24 h. Furthermore, more than 90% occupancy levels of MCH1 receptor antagonists during 24 h post-dosing are required for potent efficacy on body weight reduction. The present occupancy assay could be a useful pharmacodynamic marker to quantitatively estimate anti-obese efficacy, and would accelerate the development of MCH1 receptor antagonists for treatment of obesity.