Participants eligible for the SPIKE trial were patients with T2DM in whom the target of blood glucose control specified in the Treatment Guide for Diabetes (Edited by Japan Diabetes Society in 2010) was not achieved (HbA1c ≥ 7.0%), despite insulin therapy in addition to dietary/exercise therapy or concomitant therapeutic drugs for T2DM other than DPP-4 inhibitors over a period of 3 months or longer. Here, DPP4 is linked to type 2 diabetes mellitus.