Contrasting with this traditional approach, GCGR agonism has emerged as a credible component of combined therapeutic strategies for treating obesity and T2D in which GLP-1R and GCGR are concurrently targeted [7,8], thereby recapitulating the effects of the endogenous GLP-1R/GCGR co-agonist oxyntomodulin (OXM) [9]. This evidence concerns the gene GCGR and obesity due to melanocortin 4 receptor deficiency.