A compound of Formula I: ** Formula ** or pharmaceutically acceptable salts thereof, wherein: R1 is a saturated cyclic amino group, which may be optionally substituted by 1, 2, 3 or 4 R1a； R1a is H, halogen, cyano, C1-6 alkyl, hydroxy C1-6 alkyl, haloalkyl, cyanoalkyl, ORa, SRa, NRbRc, NRbC (O) Rd, NRbS (O) 2Rd, C (O) NRbRc, C (O) Rd, C (O) ORa, S (O) 2Rd, C2-6 alkenyl, C2-6 alkynyl, aryl, heteroaryl, cycloalkyl or heterocycloalkyl, wherein said C1-6 alkyl, C2-6 alkenyl, C2-6 alkynyl, aryl, heteroaryl, cycloalkyl and heterocycloalkyl can be optionally substituted by 1, 2 or 3 groups independently selected from the cyano, halogen, ORa, SRa, NRbRc, NRb (CO) Rd, NRbS (O) 2Rd, C (O) NRbRc groups, S (O) 2NRbRc, C (O) Rd, C (O) ORa, S (O) 2Rd, C1-6 haloalkyl, C1-6 hydroxyalkyl, C1-6 cyanoalkyl, aryl, heteroaryl, cycloalkyl and heterocycloalkyl； or two R1a groups taken together with the atoms attached thereto can form a 3, 4, 5, 6 or 7 ring cycloalkyl or a heterocycloalkyl, and can be optionally substituted by 1, 2 or 3 groups independently selected from cyano , halogen, ORa, SRa, NRbRc, NRb (CO) Rd, NRbS (O) 2Rd, C (O) NRbRc15, S (O) 2NRbRc, C (O) Rd, C (O) ORa, S (O) 2Rd , C1-6 haloalkyl, C1-6 hydroxyalkyl, C1-6 cyanoalkyl, C2-6 alkenyl, C2-6 alkynyl, aryl, heteroaryl, cycloalkyl and heterocycloalkyl； R2 is H, halogen, cyano group, ORa, SRa, NRbRc, C1-6 alkyl, C1-6 hydroxyalkyl, C1-6 haloalkyl, C1-6 cyanoalkyl, C2-6 alkenyl, C2-6 alkynyl； or two R2 groups taken together with the atoms attached thereto may form a 3, 4, 5, 6 or 7 ring cycloalkyl and heterocycloalkyl, and may be optionally substituted by 1, 2 or 3 groups independently selected from cyano, halogen, ORa, SRa, NRbRc, NRb (CO) Rd, NRbS (O) 2Rd, C (O) NRbRc, S (O) 2NRbRc, C (O) Rd, C (O) ORa, S (O) 2Rd, C 1-6 haloalkyl, C 1-6 hydroxyalkyl, C 1-6 cyanoalkyl, C 2-6 alkenyl, and C 2-6 alkynyl； R3 is H, halogen, cyano, ORa, SRa, NRbRc, C1-6 alkyl, C1-6 hydroxyalkyl, C1-6 haloalkyl, C1-6 cyanoalkyl, C2-6 alkenyl, C2-
