The FimAsartaN proTeinuriA SusTaIned reduCtion in comparison with losartan in diabetic chronic kidney disease (FANTASTIC) trial.

As angiotensin II type 1 receptor blockers (ARBs) may have different antiproteinuric effects in diabetic kidney disease (DKD), we ascertained the albuminuria-reducing effect of fimasartan and losartan in patients with DKD. This was a randomized, multicenter, double-blind, 4-parallel-group, dose-titration, phase III study designed to compare the efficacy of fimasartan and losartan in reducing albuminuria in patients with DKD (NCT02620306). The primary endpoint was the rate of change in albuminuria from baseline to week 24. A total of 341 patients were randomized to different groups. The urinary albumin-to-creatinine ratio (ACR), systolic blood pressure (SBP), and diastolic blood pressure (DBP) were not different between the fimasartan and losartan groups at baseline (ACR: 1376.84 vs. 1521.07 mg/gCr, SBP: 154.69 vs. 154.47 mmHg, DBP: 83.96 vs. 83.83 mmHg). However, ACR reduction was significantly larger in the fimasartan group than in the losartan group during the entire study period (% changes in the ACR at 4, 8, 12, and 24 weeks were -23.58, -33.06, -35.00, and -38.13 in the fimasartan group vs. -8.74, -10.17, -14.91, and -19.71 in the losartan group, p < 0.01, respectively). The superior antiproteinuric effect of fimasartan compared to losartan was still significant after adjustment for SBP levels. There were no significant differences in adverse events, including the incidences of estimated glomerular filtration decline and hyperkalemia. This study demonstrates that compared to losartan, fimasartan significantly reduces albuminuria in patients with DKD, even after adjustment for SBP and DBP.