A compound of formula (I) ** Formula ** or a pharmaceutically acceptable salt thereof for use as a medicament, wherein X1 is S； SW)； or S (O) 2； X2 is N； or C (R4)； R1 is H； or methyl； R2 is phenyl； 3 to 7 member heterocyclyl； 7 to 11-membered heterobicyclyl, wherein R2 is optionally substituted with one or more R5, which are the same or different； R5 is halogen； CN； C (O) OR6； OR6； C (O) R6； C (O) N (R6R6a)； S (O) 2N (R6R6a)； S (O) N (R6R6a)； S (O) 2R6； S (O) R6； N (R6) S (O) 2N (R6aR6b)； SR6； N (R6R6a)； OC (O) R6； N (R6) C (O) R6a； N (R6) S (O) 2R6a； N (R6) S (O) R6a； N (R6) C (O) OR6a； N (R6) C (O) N (R6aR6b)； OC (O) N (R6R6a)； oxo (= O), in which the ring is at least partially saturated； T1； C1-6 alkyl； C2-6 alkenyl； or C2-6 alkynyl, wherein C1-6 alkyl； C2-6 alkenyl； and C2-6 alkynyl are optionally substituted with one or more halogen, which are the same or different； R6, R6a, R6b are independently selected from the group consisting of H； C1-6 alkyl, C2-6 alkenyl； and C2-6 alkynyl, wherein C1-6 alkyl； C2-6 alkenyl； and C2-6 alkynyl are optionally substituted with one or more halogen, which are the same or different； T1 is phenyl； C3-7 cycloalkyl； or 3- to 7-membered heterocyclyl, in which T1 is optionally substituted with one or more R7, which are the same or different； R7 is halogen； CN； C (O) OR8； OR8； C (O) R8； C (O) N (R8R8a)； S (O) 2N (R8R8a)； S (O) N (R8R8a)； S (O) 2R8； S (O) R8； N (R8) S (O) 2N (R8aR8b)； SR8； N (R8R8a)； OC (O) R8； N (R8) C (O) R8a； N (R8) S (O) 2R8a； N (R8) S (O) R8a； N (R8) C (O) OR8a； N (R8) C (O) N (R8aR8b)； OC (O) N (R8R8a)； oxo (= O), in which the ring is at least partially saturated； C1-6 alkyl； C2-6 alkenyl； or C2-6 alkynyl, wherein C1-6 alkyl； C2-6 alkenyl； and C2-6 alkynyl are optionally substituted with one or more halogen, which are the same or different； R8, R8a, R8b are independently selected from the group consisting of H； C1-6 alkyl； C2-6 alkenyl； and C2-6 alkynyl, wherein C1-6 alkyl； C2-6 alkenyl； and C2-6 alkynyl are opti
