A compound of Formula I, or an isomer, pharmaceutically acceptable salt and solvate thereof, wherein: A represents =O; X represents F, Cl, Br or I; R 1 represents phenyl, phenyl-C1-C6 alkyl-, wherein said phenyl is unsubstituted or substituted with 1-4 (e.g., 1-2, 1, 2, 3 or 4) substituents independently selected from the group consisting of: halogens, nitro, hydroxyl, amino, cyano, C1-C6 alkyl, C1-C6 alkoxy, and C1-C6 halogenated alkyl, and wherein said alkyl, alkoxy and halogenated alkyl may be optionally substituted with hydroxyl, -O-(C1-C4)-alkyl, oxo, amino, -NH-(C1-C4)-alkyl, or -N-[(C1-C6)-alkyl] 2, or said alkyl, alkoxy and halogenated alkyl can optionally be intervened by -O-, -S-, -NH-, -COO-, or -CONH-; 5- or 6-membered heterocyclic ring or substituted heterocyclic ring; wherein said heterocyclic ring is unsubstituted or substituted with 1-3 (e.g., 1-2, 1, 2, or 3) substituents independently selected from the group consisting of: halogens, nitro, hydroxyl, amino, cyano, C1-C6 alkyl, C1-C6 alkoxy, and C1-C6 halogenated alkyl, and wherein said alkyl, alkoxy and halogenated alkyl may be optionally substituted with hydroxyl, -O-(C1-C4)-alkyl, oxo, amino, -NH-(C1-C4)-alkyl, or -N-[(C1-C6)-alkyl] 2, or said alkyl, alkoxy and halogenated alkyl can optionally be intervened by -O-, -S-, - NH-, -COO-, said heterocyclic ring may be nitrogen-nitrogen-containing heterocyclic ring, nitrogen-oxygen-containing heterocyclic ring, nitrogen-sulfur-containing heterocyclic ring; R 2 and R 3 represent hydrogen, C1-C6 alkyl, C3-C6 cycloalkyl, substituted C3-C6 cycloalkyl, C1-C6 alkoxy C1-C6 alkyl, aminoC1-C6 alkyl, mono-substituted or di-substituted aminoC1-C6 alkyl, phenyl C1-C6 alkyl, substituted phenyl C1-C6 alkyl, heterocyclic substituent C1-C6 alkyl, substituted heterocyclic substituent C1-C6 alkyl, phenyl, substituted phenyl, C1-C6 heterocyclic substituent or substituted C1-C6 heterocyclic substituent, wherein R 2 and R 3 may be attached together to form a ring. A represents =O; X represents F, Cl, Br or I; R 1 represents phenyl, phenyl-C1-C6 alkyl-, wherein said phenyl is unsubstituted or substituted with 1-4 (e.g., 1-2, 1, 2, 3 or 4) substituents independently selected from the group consisting of: halogens, nitro, hydroxyl, amino, cyano, C1-C6 alkyl, C1-C6 alkoxy, and C1-C6 halogenated alkyl, and wherein said alkyl, alkoxy and halogenated alkyl may be optionally substituted with hydroxyl, -O-(C1-C4)-alkyl, oxo, amino, -NH-(C1-C4)-alkyl, or -N-[(C1-C6)-alkyl] 2, or said alkyl, alkoxy and halogenated alkyl can optionally be intervened by -O-, -S-, -NH-, -COO-, or -CONH-; 5- or 6-membered heterocyclic ring or substituted heterocyclic ring; wherein said heterocyclic ring is unsubstituted or substituted with 1-3 (e.g., 1-2, 1, 2, or 3) substituents independently selected from the group consisting of: halogens, nitro, hydroxyl, amino, cyano, C1-C6 alkyl, C1-C6 alkoxy, and C1-C6 halogenated alkyl, and wherein said alkyl, alkoxy and halogenated alkyl may be optionally substituted with hydroxyl, -O-(C1-C4)-alkyl, oxo, amino, -NH-(C1-C4)-alkyl, or -N-[(C1-C6)-alkyl] 2, or said alkyl, alkoxy and halogenated alkyl can optionally be intervened by -O-, -S-, - NH-, -COO-, said heterocyclic ring may be nitrogen-nitrogen-containing heterocyclic ring, nitrogen-oxygen-containing heterocyclic ring, nitrogen-sulfur-containing heterocyclic ring; R 2 and R 3 represent hydrogen, C1-C6 alkyl, C3-C6 cycloalkyl, substituted C3-C6 cycloalkyl, C1-C6 alkoxy C1-C6 alkyl, aminoC1-C6 alkyl, mono-substituted or di-substituted aminoC1-C6 alkyl, phenyl C1-C6 alkyl, substituted phenyl C1-C6 alkyl, heterocyclic substituent C1-C6 alkyl, substituted heterocyclic substituent C1-C6 alkyl, phenyl, substituted phenyl, C1-C6 heterocyclic substituent or substituted C1-C6 heterocyclic substituent, wherein R 2 and R 3 may be attached together to form a ring.