Investigation of a Dipeptidyl Peptidase-4 Inhibitor/Thiazolidinedione Combination Drug for Patients With Type 2 Diabetes and Poor Glycemic Control: Difficulty With Patient Enrollment

BACKGROUND: One of the treatment options for type 2 diabetes mellitus (DM) is a combination drug (CD) that contains the dipeptidyl peptidase-4 inhibitor (DPP4I) alogliptin (AG) together with pioglitazone (PG). This CD can improve impaired insulin secretion and insulin resistance, which are the two major pathologic factors for type 2 DM, and is also expected to increase adherence to treatment. We conducted a multicenter open-label prospective study to examine the usefulness of this CD for routine management of type 2 DM. METHODS: In type 2 DM patients with poor glycemic control who had been taking a DPP4I for ≥ 1 month, PG (15 mg/day) was added (first point). When the safety of PG was confirmed after 1 - 3 months, the DPP4I and PG were switched to the CD containing AG (25 mg) and PG (15 mg) (second point). Three months after switching to the CD was defined as the final point. Evaluation of objective findings, laboratory test results, and medication adherence was performed at these three points. RESULTS: Nineteen subjects completed the study, but this was far short of the target (160 subjects). Compared to the first point, white blood cell count (WBC), aspartate aminotransferase (AST), alanine aminotransferase (ALT), γ-glutamyl transpeptidase (γ-GTP), and fasting blood glucose (FBG) all showed a significant decrease at both the second and final points. No change in medication adherence was observed throughout the study period. The most notable point about this study was the extremely small number of subjects enrolled. As a possible explanation, we considered whether the preferences of the study doctors for antidiabetic drugs differed between specialties. The study doctors were mainly gastroenterologists, followed by endocrinologists/diabetologists and cardiologists in equal numbers. As an additional investigation, we determined the percentages of specialist doctors prescribing DPP4Is, sodium-glucose cotransporter-2 inhibitors (SGLT2Is), PG, or biguanides (BGs) as the main treatment for DM in 1 month at our hospital. We found that a low percentage of endocrinologists/diabetologists prescribing PG compared to other drugs, while cardiologists prescribed PG frequently. CONCLUSIONS: It was confirmed that the combination of DPP4I with PG was effective for the treatment of type 2 DM and improving metabolic function. Our data also showed that prescription of antidiabetic drugs differed between specialties, suggesting differences in their response to the results of various clinical studies and adverse reaction reports.