DPP4 and diabetes mellitus: Furthermore, linagliptin is the first and so far only DPP-4 inhibitor to be evaluated in a randomized clinical trial designed to robustly assess renal outcomes: the ongoing Cardiovascular and Renal Microvascular Outcome Study with Linagliptin in Patients with Type 2 Diabetes Mellitus (CARMELINA®; 20ClinicalTrialsgov: NCT01897532).