A compound represented by the following structural formula: ** Formula ** or a pharmaceutically acceptable salt thereof, wherein: X is N or CRc； R1 is alkyl or -NRaRb； R2 is H； halogen； -CN； -NRC (O) R； -C (O) OR； -C (O) NRaRb； monocyclic heteroaromatic optionally substituted with one or more groups selected from alkyl, -CN, -NRC (O) R, -C (O) OR, -C (O) NRaRb and halogen； monocyclic non-aromatic heterocycle optionally substituted with one or more groups selected from alkyl, halogen, -CN and>； = O； or alkyl optionally substituted by one or more groups selected from halogen, hydroxy, alkoxy, -NRaRb, -NRC (O) R, -NRC (O) O (alkyl), -NRC (O) N (R) 2, -C (O) OR, thiol, alkylthiol, nitro, -CN,>； = O, -OC (O) H, -OC (O) (alkyl), -OC (O) O (alkyl), -OC (O) N (R) 2 and -C (O) NRaRb. R3 is alkyl, haloalkyl, hydroxyalkyl, alkoxyalkyl, cycloalkyl, monocyclic non-aromatic heterocycle, monocyclic heteroaromatic or phenyl, wherein the phenyl group, monocyclic non-aromatic heterocycle and monocyclic heteroaromatic represented by R3 are optionally substituted with one or more selected alkyl groups, halogen, haloalkyl, alkoxy, haloalkoxy, nitro and -CN. R4 and R5 are independently halogen, -CN, -OR, -SR, -N (R) 2, -C (O) R, -C (O) OR, -OC (O) O (alkyl), -C ( O) O (haloalkyl), -OC (O) R, -C (O) N (R) 2, -OC (O) N (R) 2, -NRC (O) R, -NRC (O) O ( alkyl), -S (O) R, -SO2R, -SO2N (R) 2, -NRS (O) R, -NRSO2R -NRC (O) N (R) 2, -NRSO2N (R) 2, haloalkyl, haloalkoxy , cycloalkoxy, cycloalkyl, monocyclic non-aromatic heterocycle, monocyclic heteroaromatic or alkyl, wherein the alkyl, monocyclic non-aromatic heterocycle and monocyclic heteroaromatic group represented by R4 or R5 are optionally substituted with one or more groups selected from -CN, -OR, - SR, -N (R) 2,>； = O, -C (O) R, -C (O) OR, -C (O) O (haloalkyl), -OC (O) R, -OC (O) O (alkyl), -C (O) N (R) 2, -OC (O) N (R) 2, -NRC (O) R, -NRC (O) O (alkyl), -S (O) R, -SO2R, -SO2N (R) 2, -NRS (O) R, -NRSO2R, -NRC (O) N (R) 2 and -NRSO2N (
