The present disclosure relates to the finding that certain DPP-4 inhibitors are particularly suitable for improving glycemic control in type 2 diabetes patients with inadequate glycemic control despite metformin therapy. In one embodiment the DPP-4 inhibitor is 1-[(4-methyl-quinazolin-2-yl)methyl]-3-methyl-7-(2-butyn-1-yl)-8-(3-(R)-amino-piperidin-1-yl)-xanthine and is used in combination with metformin. In a sub-embodiment the type 2 diabetes patient with inadequate glycemic control despite metformin therapy has HbA1c at baseline &ge 9 %.
