Abstract
INTRODUCTION: Metformin is widely recommended as a first-line therapy for patients with type 2 diabetes; however, evidence supporting its effects on cardiovascular outcomes is limited and derived from older studies. Furthermore, there is little direct evidence that demonstrates the protective effect of metformin on renal events. By contrast, sodium-glucose cotransporter 2 (SGLT2) inhibitors have consistently shown benefits in reducing cardiovascular and renal events. This study aims to directly compare the effects of an SGLT2 inhibitor and metformin on the urinary albumin-to-creatinine ratio (UACR), which is a marker of diabetic nephropathy and endothelial dysfunction. METHODS: This article presents the study protocol for a multicenter, randomized, open-label, controlled trial that evaluates the efficacy of the SGLT2 inhibitor tofogliflozin versus metformin on UACR in patients with type 2 diabetes and diabetic kidney disease (DKD). A total of 120 participants with an estimated glomerular filtration rate (eGFR) ≥ 30 mL/min/1.73 m(2) and UACR between 30 and 2000 mg/gCr will be enrolled. Participants will be randomized (1:1) to receive either tofogliflozin or metformin and will be stratified using baseline UACR (< 300 or ≥ 300 mg/gCr), eGFR (< 60 or ≥ 60 mL/min/1.73 m(2)), and age (< 65 or ≥ 65 years). PLANNED OUTCOMES: The primary endpoint is the change in UACR from baseline at 52 weeks. The secondary endpoints include changes in UACR at 26 and 104 weeks (absolute and percentage changes); slope of eGFR decline; and changes in hemoglobin A1c, body weight, and blood pressure. If tofogliflozin demonstrates a superior reduction in albuminuria, SGLT2 inhibitors may be considered an alternative first-line therapy in selected patients with type 2 diabetes and DKD. TRIAL REGISTRATION: jRCTs031210339; Clinicaltrials.gov (NCT05469659).