- At randomization, patients are treated for diabetes by diet and exercise, or by diet, exercise and metformin (>1000 mg/day; any type and regimen). Patients on a stable regimen of metformin (defined as the same metformin dose and type) for at least 6 weeks prior to entering the placebo run-in period. Other anti-diabetic agents not in use for the 6 weeks prior to entering the placebo run-in period;