A compound of Formula I: wherein A is B is X is deleted, (CR a' R b') m in which m is 1, 2, 3, 4, or 5, SO, SO 2, CO, COO, CONR c', NR c', or NR c' CONR d', in which each of R a', R b', R c', and R d', independently, is H or C 1-10 alkyl, in which alkyl includes both substituted and unsubstituted moieties, wherein possible substituents are C 2 -C 10 alkenyl, C 2 -C 10 alkynyl, C 3 -C 20 cycloalkyl, C 3 -C 20 cycloalkenyl, C 1 -C 20 heterocycloalkyl, C 1 -C 20 heterocycloalkenyl, C 1 -C 10 alkoxy, aryl, aryloxy, heteroaryl, heteroaryloxy, amino, C 1 -C 10 alkylamino, C 1 -C 20 dialkylamino, arylamino, diarylamino, C 1 -C 10 alkylsulfonamino, arylsulfonamino, C 1 -C 10 alkylimino, arylimino, C 1 -C 10 alkylsulfonimino, arylsulfonimino, hydroxyl, halo, thio, C 1 -C 10 alkylthio, arylthio, C 1 -C 10 alkylsulfonyl, arylsulfonyl, acylamino, aminoacyl, aminothioacyl, amido, amidino, guanidine, ureido, thioureido, cyano, nitro, nitroso, azido, acyl, thioacyl, acyloxy, carboxyl, and carboxylic ester; each of R 1 and R 2, independently, is H, halo, NR c1 C R a1, OR b1, NR c1 R d1, NR c1 C OR b1, NR c1 S 2 R b1, C 1-10 alkyl, or C 1-10 haloalkyl, in which each of R a1 and R b1, independently, is H, C 1-10 alkyl, C 1-10 haloalkyl, aryl, or heteroaryl, and each of R c1 and R d1, independently, is H, C 1-10 alkyl, C 1-10 haloalkyl, aryl, heteroaryl, or R c and R d together with the N atom to which they are attached form a 4-, 5-, 6- or 7-membered heterocycloalkyl group, in which haloalkyl refers to an alkyl group having one or more halogen substituents, and in which alkyl, heterocycloalkyl, aryl and heteroaryl include both substituted and unsubstituted moieties, wherein possible substituents on heterocycloalkyl, aryl, and heteroaryl are C 1 -C 10 alkyl, C 2 -C 10 alkenyl, C 2 -C 10 alkynyl, C 3 -C 20 cycloalkyl, C 3 -C 20 cycloalkenyl, C 1 -C 20 heterocycloalkyl, C 1 -C 20 heterocycloalkenyl, C 1 -C 10 alkoxy, aryl, aryloxy, heteroaryl, heteroaryloxy, amino, C 1 -C 10 alkylamino, C 1 -C 20 dialkylamino, arylamino, diarylamino, C 1 -C 10 alkylsulfonamino, arylsulfonamino, C 1 -C 10 alkylimino, arylimino, C 1 -C 10 alkylsulfonimino, arylsulfonimino, hydroxyl, halo, thio, C 1 -C 10 alkylthio, arylthio, C 1 -C 10 alkylsulfonyl, arylsulfonyl, acylamino, aminoacyl, aminothioacyl, amido, amidino, guanidine, ureido, thioureido, cyano, nitro, nitroso, azido, acyl, thioacyl, acyloxy, carboxyl, and carboxylic ester, and wherein cycloalkyl, cycloalkenyl, heterocycloalkyl, heterocycloalkenyl, aryl, and heteroaryl can be fused with each other, and in which possible substituents on alkyl are all of the above-recited substituents except C 1 -C 10 alkyl; and R 3 is H, halo, OC R a2, C OR b2, OR b2, SR b2, SO 2 R b2, C NR c2 R d2, NR c2 R d2, NR c2 C R a2, NR c2 C C OR a2, NR c2 S 2 R b2, C 1-10 alkyl, C 1-10 haloalkyl, aryl, haloaryl, cycloalkyl, heteroaryl, heterocycloalkyl, arylalkyl, heteroarylalkyl, cycloalkylalkyl or heterocycloalkylalkyl, in which C 1-10 alkyl, C 1-10 haloalkyl, aryl, haloaryl, cycloalkyl, heteroaryl, heterocycloalkyl, arylalkyl, heteroarylalkyl, cycloalkylalkyl or heterocycloalkylalkyl is optionally substituted by halo, C 1-4 alkyl, C 1-4 haloalkyl, aryl, heteroaryl, CN, NO 2, OR b2, C OR b2, C NR c2 R a2, or NR c2 R d2, in which each of R a2 and R b2, independently, is H, C 1-6 alkyl, C 1-6 haloalkyl, aryl, cycloalkyl, heteroaryl, heterocycloalkyl, arylalkyl, or heteroarylalkyl in which C 1-6 alkyl, C 1-6 haloalkyl, aryl, cycloalkyl, heteroaryl, heterocycloalkyl, arylalkyl, or heteroarylalkyl is optionally substituted by OH, C 1-6 alkoxyl, CN, NO 2, or halo, and each of R c2 and R d2, independently, is H, C 1-10 alkyl, C 1-10 haloalkyl, aryl, heteroaryl, cycloalkyl, heterocycloalkyl, arylalkyl, heteroarylalkyl, cycloalkylalkyl or heterocycloalkylalkyl, in which C 1-10 alkyl, C 1-10 haloalkyl, aryl, heteroaryl, cycloalkyl, heterocycloalkyl, arylalkyl, heteroarylalkyl, cycloalkylalkyl or heterocycloalkylalkyl is optionally substituted by C 1-6 alkoxyl, OH, amino, C 1-4 alkylamino, C 2-8 dialkylamino, S 2 R b2, C 1-6 alkyl, C 1-6 haloalkyl, C 1-6 haloalkyl, aryl, arylalkyl, heteroaryl, heteroarylalkyl, cycloalkyl or heterocycloalkyl, or R c2 and R d2 together with the N atom to which they are attached form a 4-, 5-, 6- or 7-membered heterocycloalkyl group, or a pharmaceutically acceptable salt thereof.