FIELD: chemistry.SUBSTANCE: invention relates to the field of organic chemistry, specifically to a heterocyclic compound of formula I, where R1a: H or halogen； R1b: halogen, C1-4-alkyl (optionally substituted with three halogens), C1-4-alkoxy group (optionally substituted with three halogens)； X: -S-, -O- or -N=CH-； W: N or CR3, when W is N, R2 is H or -CN, when W is CR3, one of R2 or R3 represents H, -CN, halogen, C1-4-alkyl (optionally substituted with one substituent selected from OH or CN), -C(=O)CH3, -C(=O)CF3, -C(=O)OCH3, -C(=O)NH2, -NHC(=O)CH3, and the other one is H or C1-4-alkyl； R4: C1-4-alkyl； R5: C1-4-alkyl optionally substituted with one or three substituents selected from CN, halogen or -C(=O)NH2； one of R6a or R6b is selected from H, -CH3 and halogen, and the other is H； Cy: 4–6 membered monocyclic heterocycloalkyl containing 1-2 heteroatoms selected from O, N and S, or 5-6 membered heterocycloalkenyl containing 1 double bond containing 1-2 heteroatoms independently selected from O, N and S； R7: OH, oxo, halogen and C1-4-alkyl； the subscript a is 0, 1, or 2； R8: -(L1-W1)m-L2-G1, where L1 is absent or represents -C(=O)-, -NRi, -NRhC(=O)- or -SO2-； W1: C1-4alkylene； the subscript m is 0 or 1； L2 is absent or represents -O-, -C(=O)-, -C(=O)O-, -OC(=O)-, -C(=O)-C(=O)-, -C(=O)-C(=O)NRa-, -NRb-, -C(=O)NRc-, -SO2- or -SO2NRe-； G1: H, -CN, C1-4-alkyl (optionally substituted with one or three substituents selected from -CN, OH, halogen or phenyl), C3-6-cycloalkyl (optionally substituted with -NH2), 5-membered heterocycloalkenyl containing 1 double bond, containing 2 heteroatoms independently selected from O and N (optionally substituted with one substituent selected from groups R9), 4–6 membered monocyclic heterocycloalkyl containing 1-2 heteroatoms independently selected from O and N (optionally substituted with one or two substituents independently selected from the groups R9), or a 5-membered heteroaryl containing 1–4 heteroatoms independently selected fr
