A CRYSTALLINE FORM OF (S)-1-(4-CHLORO-PHENYL)-7-ISOPROPOXY-6-METHOXY-2-(4-{METHYL-[4-(4-METHYL-3-OXO-PIPERAZIN-1-YL)-TRANS-CYCLOHEXYLMETHYL]-AMINO}-PHENYL)-1,4DIHYDRO-2H-ISOQUINOLIN-3-ONE, WHICH IS USEFUL IN THE TREATMENT OF A DISEASE OR DISORDER ASSOCIATED WITH THE INTERACTION BETWEEN P53, OR VARIANTS THEREOF, AND MDM2 AND/OR MDM4, OR VARIANTS THEREOF, RESPECTIVELY, (I).