Pyrimidopyrrole spiro compounds and derivatives thereof as dna-pk inhibitors

A compound represented by formula (III) or a pharmaceutically acceptable salt thereof,

• wherein,
• R5 and R6 combining with the carbon atoms to which they are attached form
• when is a single bond, E1 is selected from —O—, —S—, —C(═O)—, —S(═O)2—, —C(R1)(R2)—, —N(R3)— and
• when is a double bond, E1 is selected from —C(R1—;
• R1and R2 are each independently selected from H, OH, F, CI, Br, I, C1-3 alkoxy and C1-3 alkyl, and the C1-3 alkoxy and C1-3 alkyl are optionally substituted by 1, 2 or 3 Ra;
• or, R1and R2 combining with the carbon atoms to which they are attached form a cyclopropyl, cyclobutyl and oxetanyl;
• R3 is selected from C1-3 alkyl-C(═O)— and C1-3 alkyl, and the C1-3 alkyl-C(═O)— and C1-3 alkyl are optionally substituted by 1, 2 or 3 Rb;
• R4 is selected from C1-3 alkoxy;
• n is selected from 0, 1 and 2, provided that when E1 is selected from —C(R1)(R2)—, and both R1 and R2 are selected from H, n is not 0;
• m is selected from 1, 2 and 3;
• X1, X2, X3, X4 and X5 are each independently selected from N, C and CH, provided that at most three of X1, X2, X3, X4 and X5 are N, and the ring formed with X1, X2, X3, X4 and X5 is an aromatic ring;
• X6 is selected from CH and N;
• Y1 is selected from F, CI, Br, I, cyclopropyl and C1-3 alkyl, and the C1-3 alkyl is optionally substituted by OH or 1, 2 or 3 Ra;
• Y2 is selected from cyclopropyl and C1-3 alkyl, and the C1-3 alkyl is optionally substituted by 1, 2, 3, 4 or 5 F;
• Ra and Rb are each independently selected from H, F, Cl, Br, I.