Evaluate the safety and efficacy of RVT-1502, a novel oral glucagon receptor antagonist, in subjects with type 2 diabetes inadequately controlled on metformin. RESEARCH DESIGN AND METHODS In a phase 2, double-blind, randomized, placebo-controlled study, subjects with type 2 diabetes (n 5 166) on a stable dose of metformin were randomized (1:1:1:1) to placebo or RVT-1502 5, 10, or 15 mg once daily for 12 weeks. The primary end point was change from baseline in HbA 1c for each dose of RVT-1502 compared with placebo. Secondary end points included change from baseline in fasting plasma glucose (FPG) and safety assessments. RESULTS Over 12 weeks, RVT-1502 significantly reduced HbA 1c relative to placebo by 0.74%, 0.76%, and 1.05% in the 5-, 10-, and 15-mg groups (P < 0.001), respectively, and FPG decreased by 2.1, 2.2, and 2.6 mmol/L (P < 0.001). The proportions of subjects achieving an HbA 1c <7.0% were 19.5%, 39.5%, 39.5%, and 45.0% with placebo and RVT-1502 5, 10, and 15 mg (P £ 0.02 vs. placebo). The frequency of hypoglycemia was low, and no episodes were severe. Mild increases in mean aminotransferase levels remaining below the upper limit of normal were observed with RVT-1502 but were reversible and did not appear to be dose related, with no other liver parameter changes. Weight and lipid changes were similar between RVT-1502 and placebo. RVT-1502-associated mild increases in blood pressure were not dose related or consistent across time. CONCLUSIONS Glucagon receptor antagonism with RVT-1502 significantly lowers HbA 1c and FPG, with a safety profile that supports further clinical development with longer-duration studies (NCT02851849). Glucagon stimulates gluconeogenesis and glycogenolysis through the glucagon receptor, thereby counteracting the role of insulin in the regulation of glucose homeostasis (1). In subjects with diabetes, the normal feedback system becomes imbalanced, and glucagon secretion is dysregulated, remaining elevated in both fasting