A compound of Formula (IV-2), or a pharmaceutically acceptable salt thereof, wherein, R 1 is selected from the group consisting of H, halogen and C 1-6 alkyl; R 2 is selected from the group consisting of NH 2, C 1-6 alkyl, C 1-6 heteroalkyl, and C 2-6 alkenyl, wherein the C 1-6 alkyl, C 1-6 heteroalkyl, and C 2-6 alkenyl are optionally substituted with 1, 2 or 3 R; R 4 is selected from the group consisting of H, CN, halogen, C 1-4 alkyl, C 1-4 heteroalkyl, C 3-6 cycloalkyl, 3- to 6-membered heterocycloalkyl and 5- to 6-membered heteroaryl; R 5 and R 6 are each independently selected from the group consisting of H, NH 2, C 1-6 alkyl, C 1-6 heteroalkyl, C 3-6 cycloalkyl and 3- to 6-membered heterocycloalkyl, wherein the C 1-6 alkyl, C 1-6 heteroalkyl, C 3-6 cycloalkyl and 3- to 6-membered heterocycloalkyl are optionally substituted with 1, 2 or 3 R; L 1 and L 2 are each independently selected from the group consisting of a single bond and -C(=O)-; R is each independently selected from the group consisting of F, Cl, Br, I, OH, CN, NH 2, C 1-4 alkyl, C 1-4 heteroalkyl, C 3-6 cycloalkyl and 3- to 6-membered heterocycloalkyl, wherein the C 1-4 alkyl, C 1-4 heteroalkyl, C 3-6 cycloalkyl and 3- to 6-membered heterocycloalkyl are optionally substituted with 1, 2 or 3 R'; R' is selected from the group consisting of F, Cl, Br, I, OH, CN, NH 2, CH 3, CF 3, CHF 2, CH 3 O, CH 3 CH 2, CH 3 CH 2 O, COOH, NH(CH 3), N(CH 3) 2, and the C 1-6 heteroalkyl, 3- to 6-membered heterocycloalkyl, 5- to 6-membered saturated heterocycle, C 1-4 heteroalkyl and 5- to 6-membered heteroaryl each independently contains 1, 2 or 3 heteroatoms or heteroatom groups selected from the group consisting of N, -NH-, -O-, -S-, =O, =S, -C(=O)O-, -C(=O)-, -C(=0)NH-, -C(=S)-, -S(=O)-, -S(=O) 2 -, -C(=NH)-, -S(=0) 2 NH-, -S(=O)NH-, and -NHC(=0)NH-. R 1 is selected from the group consisting of H, halogen and C 1-6 alkyl; R 2 is selected from the group consisting of NH 2, C 1-6 alkyl, C 1-6 heteroalkyl, and C 2-6 alkenyl, wherein the C 1-6 alkyl, C 1-6 heteroalkyl, and C 2-6 alkenyl are optionally substituted with 1, 2 or 3 R; R 4 is selected from the group consisting of H, CN, halogen, C 1-4 alkyl, C 1-4 heteroalkyl, C 3-6 cycloalkyl, 3- to 6-membered heterocycloalkyl and 5- to 6-membered heteroaryl; R 5 and R 6 are each independently selected from the group consisting of H, NH 2, C 1-6 alkyl, C 1-6 heteroalkyl, C 3-6 cycloalkyl and 3- to 6-membered heterocycloalkyl, wherein the C 1-6 alkyl, C 1-6 heteroalkyl, C 3-6 cycloalkyl and 3- to 6-membered heterocycloalkyl are optionally substituted with 1, 2 or 3 R; L 1 and L 2 are each independently selected from the group consisting of a single bond and -C(=O)-; R is each independently selected from the group consisting of F, Cl, Br, I, OH, CN, NH 2, C 1-4 alkyl, C 1-4 heteroalkyl, C 3-6 cycloalkyl and 3- to 6-membered heterocycloalkyl, wherein the C 1-4 alkyl, C 1-4 heteroalkyl, C 3-6 cycloalkyl and 3- to 6-membered heterocycloalkyl are optionally substituted with 1, 2 or 3 R'; R' is selected from the group consisting of F, Cl, Br, I, OH, CN, NH 2, CH 3, CF 3, CHF 2, CH 3 O, CH 3 CH 2, CH 3 CH 2 O, COOH, NH(CH 3), N(CH 3) 2, and the C 1-6 heteroalkyl, 3- to 6-membered heterocycloalkyl, 5- to 6-membered saturated heterocycle, C 1-4 heteroalkyl and 5- to 6-membered heteroaryl each independently contains 1, 2 or 3 heteroatoms or heteroatom groups selected from the group consisting of N, -NH-, -O-, -S-, =O, =S, -C(=O)O-, -C(=O)-, -C(=0)NH-, -C(=S)-, -S(=O)-, -S(=O) 2 -, -C(=NH)-, -S(=0) 2 NH-, -S(=O)NH-, and -NHC(=0)NH-.