INS and type 2 diabetes mellitus: Development studies with five DPP-4 inhibitors: number of examined subjects and placebo-adjusted change in HA1c when DPP-4 inhibitors were added to drug-naïve subjects with type 2 diabetes or as add-on to metformin, sulfonylurea, thiazolidinediones, or insulin in placebo-controlled 24 or 26 week studies.