AACR 2021: Anti-GCGR in vivo efficacy evaluated in a new humanized hGCGR mouse model
GCGR (glucagon receptor) is a G-protein-coupled seven-transmembrane protein, a typical representative of the class B GPCR family. Animals homozygous for a targeted mutation in this gene exhibit reduced blood glucose levels, increased plasma glucagon and amino acid levels associated with alpha-cell hyperplasia. Glucagon activates intracellular adenylate cyclase by specifically binding to GCGR on the surface of target cells in the liver. This results in an increase in intracellular cAMP levels, playing a role in promoting glycogenolysis and gluconeogenesis, and promoting blood glucose elevation. The crucial role in the regulation of blood glucose levels and glucose homeostasis is posing GCGR as a potential drug target for type 2 diabetes and related diseases. Currently, much attention and many resources are directed towards the research and development of antibody drugs targeting the glucagon receptor. Joining these efforts, Biocytogen has developed a GCGR humanized mouse model (B-hGCGR mouse). Human GCGR protein and mRNA were detected in liver tissue of homozygous B-hGCGR mice, but not in wild-type mice. Physiological indexes have been analyzed. Results indicated that the random blood glucose, fasting blood glucose, and glucose tolerance was comparable to the wild-type mice. In addition, we characterized the ability of glucagon to stimulate the production of cAMP. We observed that glucagon elicits a dose-specific increase of cAMP in membranes prepared from the humanized GCGR mice comparable to the cAMP levels observed in membranes prepared from wild-type mice. In pharmacodynamic experiments using B-hGCGR mice, we showed that an anti-GCGR antibody (Crotedumab) was able to effectively reduce random blood glucose and fasting blood glucose levels and improve glucose tolerance, validating our humanized mouse model. This antibody also blocked the functional response to glucagon in B-hGCGR mice more efficiently than what can be observed in an approach targeting the wild-type murine receptor using antagonists. These data demonstrate that B-hGCGR mice are a promising model for preclinical in vivo pharmacodynamic assessment of anti-GCGR antibodies.