Effects of exenatide (exendin-4) on glycemic control and weight over 30 weeks in metformin-treated patients with type 2 diabetes

This phase III, randomized, double-blind, placebo-controlled study evaluated the efficacy and safety of exenatide as adjunctive therapy to metformin in 336 patients with inadequately controlled type 2 diabetes. Participants were randomized to exenatide 5 µg, 10 µg (twice daily), or placebo, while maintaining stable metformin during 30 weeks.

Exenatide 10 µg produced an HbA1c reduction of -0.78% from baseline, compared to +0.08% in the placebo group (p<0.002). Impressively, 46% of patients in the high-dose group achieved HbA1c ≤7%. The combination with metformin proved particularly favorable, as the risk of hypoglycemia was minimal — metformin does not directly stimulate insulin secretion, and exenatide has glucose-dependent insulin secretion.

Weight loss was a consistent finding, with progressive reduction of -2.8 kg in the exenatide 10 µg group by study end. This result reinforced the observation that exenatide's effects on weight are independent of nausea, as weight loss continued even after the resolution of initial gastrointestinal symptoms.

The data from this study, combined with the Buse et al. (2004) trial, formed the evidence base for the regulatory approval of exenatide, consolidating the GLP-1 agonist class as a therapeutic option with dual benefit — effective glycemic control without the adverse metabolic effects of weight gain typical of other antidiabetic therapies.