In comparison to the peptidyl glucagon receptor antagonist des-His1-Glu9-glucagon (28), the anti-glucagon Spiegelmer NOX-G15 was able to lower glucose excursion in ipGTT (1.5 h post substance administration) in both animal models of T1DM and T2DM, whereas the glucagon receptor antagonist des-His1-Glu9-glucagon only proved efficacious in T2DM. This evidence concerns the gene GCGR and type 2 diabetes mellitus.