Substituted imidazolidin-2-one derivatives as prmt5 inhibitors

A compound of formula (I):

• or a pharmaceutically acceptable salt thereof or a stereoisomer thereof;
• wherein,
• each X1, X2 and X3 are independently CR5 or N;
• ring A is cycloalkyl, aryl, heterocycloalkyl or heteroaryl;
• R is hydrogen, alkyl or halo;
• R1 is
• R2 is hydrogen or alkyl;
• alternatively, R1 and R2 together with the nitrogen to which they are attached form a bicyclic heterocyclyl ring optionally containing 1 to 3 additional heteroatoms selected from N, O and S;
• wherein the bicyclic heterocyclyl ring is optionally substituted by one or more R6;
• R3 is hydrogen or alkyl;
• R4 at each occurrence independently is hydrogen, halo, haloalkyl, cyano, alkyl, alkenyl, alkynyl, hydroxy, alkoxy, —C(O)R7, -alkyl-C(O)R7, —S(O)2R7;
• wherein the said alkyl, alkenyl and alkynyl are optionally substituted with 1 to 3 groups selected from hydroxyl, halo, heterocycloalkyl and heteroaryl;
• alternatively, two R4 on the same atom together form an oxo (═O) group;
• R5 at each occurrence independently is hydrogen, alkyl, halo, haloalkyl or alkoxy;
• R6 is alkyl, alkoxy, hydroxy, cyano, halo, or haloalkyl;
• R7 is alkyl, hydroxy, alkoxy, —NReRf, cycloalkyl, aryl, heterocycloalkyl or heteroaryl;
• wherein each alkyl, cycloalkyl, aryl, heterocycloalkyl and heteroaryl is further optionally substituted by one or more R6;
• Ra and Rb each independently are hydrogen or alkyl;
• Rc and Rd each independently are hydrogen or alkyl;
• alternatively Rc and Rd together represent an oxo (═O) group;
• Re and Rf, each independently are hydrogen or alkyl;
• alternatively, Re and Rf, together with the nitrogen to which they are attached form an optionally substituted 3 to 7 membered heterocyclic ring with 1 to 2 additional heteroatoms selected from N, O and S;
• wherein the optional substituent is one or more R6;
• ‘m’ is an integer from 1 to 3;
• and
• ‘n’ is 0 or 1.