GCG and type 2 diabetes mellitus: Two new categories of T2D drugs, however, have been developed based on the glucose-lowering effect of GLP-1: GLP-1 analogs such as exenatide (or exendin-4) and liraglutide, and inhibitors of DPP-IV such as sitagliptin and vildagliptin (Wideman and Kieffer, 2009).