Substituted fused heterocyclic compound, and preparation method therefor and use thereof

A compound having a structure of formula I, or a pharmaceutically acceptable salt thereof,

• wherein,
• Y1, Y2, Y3 and Y4 are each independently CH or N, and at least one of Y1 and Y2 is N, and at least one of Y3 and Y4 is CH;
• R1 is a 5:6 ring-fused heteroaromatic cyclic group or a 6:6 ring-fused heteroaromatic cyclic group containing n heteroatoms, or a 5-membered or 6-membered aromatic cyclic group containing m heteroatoms, wherein n is an integer selected from 1 to 4, m is an integer selected from 0 to 3, and the heteroatoms are selected from one or two of O, N, and S;
• the 5:6 ring-fused heteroaromatic cyclic group or 6:6 ring-fused heteroaromatic cyclic group containing n heteroatoms is optionally substituted with one or more substituents selected from halogen, —OH, —OMe, —NH2, —NHMe, —NMe2, —CN, —CONH2, and -Me;
• the 5-membered or 6-membered aromatic cyclic group containing m heteroatoms is optionally substituted with one or more substituents selected from a 4- to 6-membered heterocycloalkyl, halogen, —OH, —OMe, —NH2, —NHMe, —NMe2, —CN, —CONH2, and -Me;
• when the aromatic cyclic group is substituted with a 4- to 6-membered heterocycloalkyl, they are connected via a single bond or joined together to share one or more member atoms;
• R2 is —OH, a C1-6 alkoxy, —NR3R4, —CN, a C1-6 alkyl, a C2-6 alkenyl, a C2-6 alkynyl, a C3-6 cycloalkyl, or a 4- to 6-membered heterocycloalkyl, wherein the heteroatom is selected from one of O and N;
• the C1-6 alkyl, C2-6 alkenyl, C2-6 alkynyl, C3-6 cycloalkyl, or the 4- to 6-membered heterocycloalkyl is optionally substituted with one or more substituents selected from halogen, —OH, a C1-6 alkoxy, —NR5R6, and —CN;
• R3 and R4 are each independently hydrogen or a C1-6 alkyl;
• and
• R5 and R6 are each independently hydrogen or a C1-6 alkyl, or —NR5R6 as a whole represents azetidinyl, tetrahydropyrrolyl, piperidinyl, morpholinyl, or 4-methylpiperazinyl.