Refers to compounds dihidropiridazin - 3.5 - dione Derivatives of formula (i) wherein R1, R3, R4, R5 and AR1 are as defined in the description.Preferred compounds are: (4AR) - 1 - [(2,3 - difluorofenil) methyl] - 4 - hydroxy - 4 - methyl - 2 - oxo -, N - [4 - (trifluoromethyl) - 2 - [6 - (trifluoromethyl) pyrimidin-4-yl] phenyl] - 6.7 - dihydro - 5h pyrrolo [1,2-b] pyridazin-3 3 - carboxamide (4AR) - N - [2 - (6 - cyano - 4 - 5 - metilpirimidin - yl) - 4 - (trifluoromethyl) phenyl] - 3 - [1 - [4 - (2 - difluoro - Mor Folin - 4 - iletoxi) phenyl] methyl] - 4 - hydroxy - 4 - methyl - 2 - oxo - 6.7 - dihydro - 5h pyrrolo [12 - 3 - B] pyridazin-3 carboxamide among others. It also relates to a Pharmaceutical composition. These compounds are inhibitors of the sodium dependent phosphate transporter to be useful for the treatment of hyperphosphatemia in chronic renal failureSE REFIERE A COMPUESTOS DERIVADOS DE DIHIDROPIRIDAZIN-3,5-DIONA DE FORMULA (I) DONDE R1, R3, R4, R5 Y Ar1 SON TAL COMO SE DEFINE EN LA DESCRIPCION. SON COMPUESTOS PREFERIDOS: (4aR)-1-[(2,3-DIFLUOROFENIL)METIL]-4-HIDROXI-4a-METIL-2-OXO-N-[4-(TRIFLUOROMETIL)-2-[6-(TRIFLUOROMETIL)PIRIMIDIN-4-IL]FENIL]-6,7-DIHIDRO-5H-PIRROLO[1,2-b]PIRIDAZIN-3-CARBOXAMIDA (4aR)-N-[2-(6-CIANO-5-METILPIRIMIDIN-4-IL)-4-(TRIFLUOROMETIL)FENIL]-1-[[2,3-DIFLUORO-4-(2-MORFOLIN-4-ILETOXI)FENIL]METIL]-4-HIDROXI-4a-METIL-2-OXO-6,7-DIHIDRO-5H-PIRROLO[1,2-b]PIRIDAZIN-3-CARBOXAMIDA ENTRE OTROS. TAMBIEN SE REFIERE A UNA COMPOSICION FARMACEUTICA. DICHOS COMPUESTOS SON INHIBIDORES DEL TRANSPORTADOR DE FOSFATO DEPENDIENTE DE SODIO SIENDO UTILES PARA EL TRATAMIENTO DE HIPERFOSFATEMIA, INSUFICIENCIA RENAL CRONICA
