In summary, the GLP1R antagonistic antibody Glp1R0017, developed and extensively characterised here, provides a novel tool for investigating the GLP-1 component of unimolecular dual agonists for the treatment of type 2 diabetes, and for further understanding the physiology of GLP1R in vitro and in vivo. The gene discussed is GCG; the disease is type 2 diabetes mellitus.