Dihydro pyridazin-3,5-dione derivatives

PROBLEM TO BE SOLVED: To provide a novel compound that is a sodium-dependent phosphate transporter inhibitor, useful for developing a preventive and/or therapeutic agent for hyperphosphatemia, secondary hyperparathyroidism, and chronic renal failure, and a method for prevention and/or treatment.SOLUTION: Provided are a dihydropyridazine-3,5-dione derivative represented by formula (I), a salt thereof, and solvates of them. [R1, R4 and R5 represent H, alkyl, or together form cycloalkyl or the like; R3 is a C1-10 alkyl or the like; Ar1 is a C6-10 aryl or 5-10 membered heteroaryl].SELECTED DRAWING: None