A compound of Formula I: or a pharmaceutically acceptable salt thereof, wherein: R 1 is selected from: amino-C 1 -C 6 alkyl, amino-aryl, amino-C 3 -C 7 cycloalkyl, amino-heterocyclyl, and heterocyclyl, each optionally substituted with one or more substituents selected from aryl, aryl-C 1 -C 6 alkyl, C 1 -C 6 alkyl, C 1 -C 6 alkylthio, carboxyl, carboxamide, C 3 -C 7 cycloalkyl, C 3 -C 7 cycloalkyl-C 1 -C 6 alkyl, guanidino, halo, C 1 -C 6 haloalkyl, heterocyclyl, heterocyclyl-C 1 -C 6 alkyl, hydroxyl, and thio; or R 1 is R a R b NCH(R c)-; R a is selected from: H and C 1 -C 6 alkyl; R b is C 1 -C 6 alkyl; and R c is R d -C(CH 3) 2 -; and R d is selected from: H, aryl, C 3 -C 7 cycloalkyl, and heteroaryl, each of which is optionally substituted with one or more substituents selected from: C 1 -C 4 acylthio, C2-C4 alkenyl, C 1 -C 4 alkyl, C 1 -C 4 alkylamino, C 1 -C 4 alkyloxy, amino, amino-C 1 -C 4 alkyl, halo, C 1 -C 4 haloalkyl, hydroxyl, hydroxy-C 1 -C 4 alkyl, and thio, wherein C 2 -C 4 alkenyl, C 1 -C 4 alkylamino and C 1 -C 4 alkyloxy are further optionally substituted with one substituent selected from C 1 -C 4 alkylaryl, hydroxyl, and thio; or R b and R c taken together with the atoms to which they are each bonded form a heterocyclyldiyl; R 2 is selected from: C 1 -C 6 alkyl, aryl, aryl-C 1 -C 6 alkyl, C 3 -C 7 cycloalkyl, C 3 -C 7 cycloalkyl-C 1 -C 6 alkyl, heteroaryl, heteroaryl-C 1 -C 6 alkyl, and heterocyclyl, each optionally substituted with one or more substituents selected from: C 1 -C 6 alkoxy, C 1 -C 6 alkoxycarbonyl, C 1 -C 6 alkyl, C 1 -C 6 alkylamino, amino, amino-C 1 -C 6 alkyl, amino-aryl, amino-C 3 -C 7 cycloalkyl, aryl, carboxamide, carboxyl, cyano, C 1 -C 6 haloacyl, C 1 -C 6 haloalkyl, C 1 -C 6 haloalkoxy, halo, hydroxyl, nitro, thio, and thio-C 1 -C 6 alkyl; and X is absent. R 1 is selected from: amino-C 1 -C 6 alkyl, amino-aryl, amino-C 3 -C 7 cycloalkyl, amino-heterocyclyl, and heterocyclyl, each optionally substituted with one or more substituents selected from aryl, aryl-C 1 -C 6 alkyl, C 1 -C 6 alkyl, C 1 -C 6 alkylthio, carboxyl, carboxamide, C 3 -C 7 cycloalkyl, C 3 -C 7 cycloalkyl-C 1 -C 6 alkyl, guanidino, halo, C 1 -C 6 haloalkyl, heterocyclyl, heterocyclyl-C 1 -C 6 alkyl, hydroxyl, and thio; or R 1 is R a R b NCH(R c)-; R a is selected from: H and C 1 -C 6 alkyl; R b is C 1 -C 6 alkyl; and R c is R d -C(CH 3) 2 -; and R d is selected from: H, aryl, C 3 -C 7 cycloalkyl, and heteroaryl, each of which is optionally substituted with one or more substituents selected from: C 1 -C 4 acylthio, C2-C4 alkenyl, C 1 -C 4 alkyl, C 1 -C 4 alkylamino, C 1 -C 4 alkyloxy, amino, amino-C 1 -C 4 alkyl, halo, C 1 -C 4 haloalkyl, hydroxyl, hydroxy-C 1 -C 4 alkyl, and thio, wherein C 2 -C 4 alkenyl, C 1 -C 4 alkylamino and C 1 -C 4 alkyloxy are further optionally substituted with one substituent selected from C 1 -C 4 alkylaryl, hydroxyl, and thio; or R b and R c taken together with the atoms to which they are each bonded form a heterocyclyldiyl; R 2 is selected from: C 1 -C 6 alkyl, aryl, aryl-C 1 -C 6 alkyl, C 3 -C 7 cycloalkyl, C 3 -C 7 cycloalkyl-C 1 -C 6 alkyl, heteroaryl, heteroaryl-C 1 -C 6 alkyl, and heterocyclyl, each optionally substituted with one or more substituents selected from: C 1 -C 6 alkoxy, C 1 -C 6 alkoxycarbonyl, C 1 -C 6 alkyl, C 1 -C 6 alkylamino, amino, amino-C 1 -C 6 alkyl, amino-aryl, amino-C 3 -C 7 cycloalkyl, aryl, carboxamide, carboxyl, cyano, C 1 -C 6 haloacyl, C 1 -C 6 haloalkyl, C 1 -C 6 haloalkoxy, halo, hydroxyl, nitro, thio, and thio-C 1 -C 6 alkyl; and X is absent.