Very potent and selective, non-competitive antagonist of the human glucagon receptor (hGR). Binds with high affinity to human GR (IC 50 = 3.7 nM), and moderate affinity to murine and canine GRs (IC 50 values are 63 and 60 nM respectively). In contrast, displays poor affinity for rat, guinea pig, and rabbit glucagon receptors (IC 50 > 1 μ M). In functional studies, inhibits glucagon-stimulated cAMP synthesis in CHO cells expressing hGR (IC 50 = 41 nM), and in murine liver membranes. Orally active in vivo .