The 24-week randomized double-blind placebo-controlled study compared vildagliptin 50mg , q.d. , with placebo as add-on to glimepiride in T2DM patients who were inadequately controlled ( HbA1c 7.5 % -11.0 % [ 58-97mmol / mol ] ) on a stable dose of sulfonylurea for 12 weeks before study entry .