A compound of formula (I) wherein A is selected from the group consisting of A1 and A2 X 1 and X 2 are independently C or N; R 1 is H or is selected from the group consisting of -NR 3 R 4 , -C(O)NR 3 R 5 , - NR 3 C(O)R 6 and -C(O)OR 7 ; R 2 is H or is selected from the group consisting of -C(O)OR 3 and -C(O)NR 3 R 6 ; or R 2 is absent when X 1 or X 2 is N; R 3 is H or -(C 1 -C 6 )alkyl; R 4 is H or -(C 1 -C 6 )alkyl; R 5 is H or is selected from the group consisting of -(C 1 -C 6 )alkyl, -(C 1- C 6 )alkylene-NR A R B , cycloalkyl, heterocycloalkyl optionally substituted by one or more -(C 1 -C 6 )alkyl, and -(C 1- C 6 )alkylene-heterocycloalkyl, wherein said heterocycloalkyl is optionally substituted by one or more groups selected from -(C 1 -C 6 )alkyl, -C(O)-(C 1- C 6 )alkyl and -SO 2 -(C 1- C 6 )alkyl; R 6 is selected from the group consisting of -(C 1- C 6 )alkylene-NR 3 R 4 and -(C 1- C 6 )alkylene-heterocycloalkyl, wherein said heterocycloalkyl is optionally substituted by one or more -(C 1 -C 6 )alkyl; R 7 is H or is selected from the group consisting of -(C 1 -C 6 )alkyl, -(C 1- C 6 )alkylene-NR 3 R 4 and -(C 1- C 6 )alkylene-heterocycloalkyl, wherein said heterocycloalkyl is optionally substituted by one or more -(C 1 -C 6 )alkyl; R A is H or is selected from the group consisting of -(C 1- C 6 )alkyl and -(C 1 -C 6 )hydroxyalkyl; R B is selected from the group consisting of -(C 1 -C 6 )alkyl, -(C 1- C 6 )alkylene-C(O)O-(C 1- C 6 )alkyl, heterocycloalkyl and -(C 1 -C 6 )hydroxyalkyl; R 8 is selected from the group consisting of aryl and heteroaryl, wherein said aryl is optionally substituted by one or more groups selected from halogen atoms, -(C 1- C 6 )alkyl and -(C 1 -C 4 )haloalkyl, and said heteroaryl is optionally substituted by one or more groups selected from -(C 1 -C 6 )alkyl, halogen atoms and -O-(C 1 -C 6 )alkyl; and pharmaceutically acceptable salts thereof. A is selected from the group consisting of A1 and A2 X 1 and X 2 are independently C or N; R 1 is H or is selected from the group consisting of -NR 3 R 4 , -C(O)NR 3 R 5 , - NR 3 C(O)R 6 and -C(O)OR 7 ; R 2 is H or is selected from the group consisting of -C(O)OR 3 and -C(O)NR 3 R 6 ; or R 2 is absent when X 1 or X 2 is N; R 3 is H or -(C 1 -C 6 )alkyl; R 4 is H or -(C 1 -C 6 )alkyl; R 5 is H or is selected from the group consisting of -(C 1 -C 6 )alkyl, -(C 1- C 6 )alkylene-NR A R B , cycloalkyl, heterocycloalkyl optionally substituted by one or more -(C 1 -C 6 )alkyl, and -(C 1- C 6 )alkylene-heterocycloalkyl, wherein said heterocycloalkyl is optionally substituted by one or more groups selected from -(C 1 -C 6 )alkyl, -C(O)-(C 1- C 6 )alkyl and -SO 2 -(C 1- C 6 )alkyl; R 6 is selected from the group consisting of -(C 1- C 6 )alkylene-NR 3 R 4 and -(C 1- C 6 )alkylene-heterocycloalkyl, wherein said heterocycloalkyl is optionally substituted by one or more -(C 1 -C 6 )alkyl; R 7 is H or is selected from the group consisting of -(C 1 -C 6 )alkyl, -(C 1- C 6 )alkylene-NR 3 R 4 and -(C 1- C 6 )alkylene-heterocycloalkyl, wherein said heterocycloalkyl is optionally substituted by one or more -(C 1 -C 6 )alkyl; R A is H or is selected from the group consisting of -(C 1- C 6 )alkyl and -(C 1 -C 6 )hydroxyalkyl; R B is selected from the group consisting of -(C 1 -C 6 )alkyl, -(C 1- C 6 )alkylene-C(O)O-(C 1- C 6 )alkyl, heterocycloalkyl and -(C 1 -C 6 )hydroxyalkyl; R 8 is selected from the group consisting of aryl and heteroaryl, wherein said aryl is optionally substituted by one or more groups selected from halogen atoms, -(C 1- C 6 )alkyl and -(C 1 -C 4 )haloalkyl, and said heteroaryl is optionally substituted by one or more groups selected from -(C 1 -C 6 )alkyl, halogen atoms and -O-(C 1 -C 6 )alkyl; and pharmaceutically acceptable salts thereof. <EOS>