An amide derivative of formula or a pharmaceutically acceptable salt thereof: wherein, A is R 4, R 5, R 6 and R 7 being each independently hydrogen, halogen, N -C 1-6 alkyl or N -hydroxy amido or C -C 1-6 alkyl reverse amido(-NHCOC 1-6), hydroxycarbonyl (-COOH), C 1-6 alkyloxycarbonyl (-COOC 1-6), C 1-6 alkyl, or C 1-6 alkyl substituted with a hydroxy, C 1-6 dialkylamine or heterocyclic group; R 1 is an aryl substituted with one to five X, heterocyclic group substituted with one to five X or C 1-6 alkyl substituted with aryl; R 2 is hydrogen, hydroxy, C 1-6 alkoxy, or C 1-6 alkoxy substituted with C 1-6 alkoxy or heterocyclic group; R 3 is hydrogen, -COOH, C 1-6 alkyloxycarbonyl, or amido N -unsubstituted or N- substituted with Y; n a and n b are each an integer ranging from 2 to 6; in which: X is hydrogen, halogen, hydroxy, cyano, nitro, (mono-, di-, or trihalogeno)methyl, mercapto, C 1-6 alkylthio, acrylamido, C 1-6 alkyl, C 1-6 alkenyl, C 1-6 alkynyl, C 1-6 alkoxy, aryloxy, C 1-6 dialkylamino, or C 1-6 alkyl or C 1-6 alkoxy substituted with Z, with the proviso that when the number of X is two or more, the X groups can fuse together to form a ring structure; Y is hydroxy, C 1-6 alkyl or C 1-6 alkyl substituted with Z, the C 1-6 alkyl containing one to four of the moiety selected from the group consisting of N, O, S, SO, and SO 2; and Z is a C 1-6 alkyl, aryl, or heterocyclic group, said aryl group being C 5-12 monocyclic or bicyclic aromatic group, said heterocyclic group being a C 5-12 monocyclic or bicyclic aromatic or non-aromatic group containing one to four of the moiety selected from the group consisting of N, O, S, SO, and SO 2 and said aryl and heterocyclic group being unsubstituted, or substituted with substituents selected from the group consisting of halogen, hydroxyl, amino, nitro, cyano, C 1-6 alkyl, C 1-6 alkenyl, C 1-6 alkynyl, C 1-6 alkoxy, C 1-6 monoalkylamino and C 1-6 dialkylamino; and wherein the term alkyl refers to saturated monovalent hydrocarbon radicals having straight, cyclic or branched moieties. X is hydrogen, halogen, hydroxy, cyano, nitro, (mono-, di-, or trihalogeno)methyl, mercapto, C 1-6 alkylthio, acrylamido, C 1-6 alkyl, C 1-6 alkenyl, C 1-6 alkynyl, C 1-6 alkoxy, aryloxy, C 1-6 dialkylamino, or C 1-6 alkyl or C 1-6 alkoxy substituted with Z, with the proviso that when the number of X is two or more, the X groups can fuse together to form a ring structure; Y is hydroxy, C 1-6 alkyl or C 1-6 alkyl substituted with Z, the C 1-6 alkyl containing one to four of the moiety selected from the group consisting of N, O, S, SO, and SO 2; and Z is a C 1-6 alkyl, aryl, or heterocyclic group, said aryl group being C 5-12 monocyclic or bicyclic aromatic group, said heterocyclic group being a C 5-12 monocyclic or bicyclic aromatic or non-aromatic group containing one to four of the moiety selected from the group consisting of N, O, S, SO, and SO 2 and said aryl and heterocyclic group being unsubstituted, or substituted with substituents selected from the group consisting of halogen, hydroxyl, amino, nitro, cyano, C 1-6 alkyl, C 1-6 alkenyl, C 1-6 alkynyl, C 1-6 alkoxy, C 1-6 monoalkylamino and C 1-6 dialkylamino; and wherein the term alkyl refers to saturated monovalent hydrocarbon radicals having straight, cyclic or branched moieties.