According to the standard of care, when a patient fails to reach their HbA1c target with dual therapy of metformin plus insulin, a third agent should be prescribed, such as thiazolidinedione, DPP-4 inhibitor, SGLT2 inhibitor, or GLP-1 receptor agonist.9 However, despite the wide availability of multiple classes of therapeutic agents, most insulin users have HbA1c well above the accepted targets and their diabetes is uncontrolled.13 This evidence concerns the gene DPP4 and diabetes mellitus.