Rationale and study design of a randomized controlled trial to investigate the renoprotective effect of canagliflozin assessed by test of renal hemodynamics in diabetic kidney disease (the FAGOTTO study)

Abstract Background Sodium-glucose cotransporter 2 inhibitors (SGLT2i) are considered to have the potential to maintain renal function by correcting glomerular hypertension in patients with diabetic kidney disease (DKD). The aim of this study is to demonstrate the renoprotective effect of SGLT2i by measuring renal hemodynamics, including glomerular filtration fraction (FF), in type 2 diabetic patients with moderate renal dysfunction. Methods Renoprotective effect of canagliflozin derived from test of renal hemodynamics in diabetic kidney disease (FAGOTTO) study is a 12-week multicenter, open-label, randomized (1:1), parallel-group trial of type 2 diabetic patients with diabetic kidney disease (30 ≤ estimated glomerular filtration rate [eGFR] ≤ 60 mL/min/1.73 m2). A total of 110 patients are to be randomly allocated to receive once-daily canagliflozin 100 mg or control (standard therapy). FF will be calculated by dividing the measured GFR (mGFR) by the effective renal plasma flow (eRPF). mGFR and eRPF will be measured by the clearance of inulin and para-aminohippuric acid (PAH), respectively. The primary endpoint of this trial is the percentage change in FF after 4 weeks of treatment in the canagliflozin and control groups. Discussion The FAGOTTO study will elucidate the mechanism of the renoprotective action of SGLT2i. The background, rationale, and study design of this trial are presented. To date, > 80 patients have been enrolled in this trial. The study will end in 2025. Trial registration jRCT (Japan Registry Of Clinical Trials) jRCTs041200069. Date of registration: November 27, 2020.