Class of polycyclic compounds inhibiting RNA helicase DHX33 and the application thereof

A compound having the structure of formula III or a pharmaceutically acceptable form thereof:

• wherein
• X1 is N or CR1, X2 is N or CR2, X3 is N or CR3, X4 is N or CR4, provided that one of X1, X2, X3 and X4 is N;
• R1, R2, R3 and R4 are each independently hydrogen, halogen, amino, nitro, hydroxyl, C1-4 alkyl, C1-4 haloalkyl, C1-4 alkoxy, C1-4 haloalkoxy, —NH(C1-4 alkyl), or —N(C1-4 alkyl)2;
• X5 is N, X6 is NR6;
• R6 is hydrogen, or C1-4 alkyl;
• R10 is hydrogen, or C1-4 alkyl;
• R9 is cyano;
• ring A is a pyrrole ring;
• ring A is optionally substituted with one or more R11;
• each R11 is independently halogen, C1-4 alkyl, or C1-4 haloalkyl;
• ring B is a furan ring, a thiophene ring, or a thiazole ring;
• ring B is optionally substituted with one or more R12;
• each R12 is independently halogen, cyano, amino, nitro, hydroxyl, C1-4 alkyl, C1-4 haloalkyl, C1-4 alkoxy, C1-4 haloalkoxy, C3-6 cycloalkyl, —C(═O)—O—(C1-4 alkyl), phenyl, benzyl, pyridyl, or —C(═O)—NH2, said phenyl, benzyl and pyridyl are optionally substituted with one or more substituents selected from hydrogen, halogen, cyano, amino, hydroxyl, C1-4 alkyl and C1-4 alkoxy;
• and
• said pharmaceutically acceptable form is a pharmaceutically acceptable salt.