During the enrollment period for the CHanges to Treatment and Outcomes in Patients with Type 2 Diabetes Initiating Injectable Therapy (CHOICE) study, exenatide twice daily (b.i.d.), the first approved glucagon-like peptide-1 (GLP-1) receptor agonist, was available in Europe for use in combination with metformin and/or a sulfonylurea in patients with type 2 diabetes mellitus (T2DM) with insufficient glycemic control on maximal doses of these medications. This evidence concerns the gene GLP1R and type 2 diabetes mellitus.