A compound of Formula I: or a pharmaceutically acceptable salt, an optical isomer, or a mixture of optical isomers thereof; wherein: W is N or CR 5; X is N or CR 6; Y is N or CR 7; and Z is N or CR 8; provided not more than two of W, X, Y, and Z are N; R 1 is selected from H and C 1 -C 3 alkyl; R 2 is C 2 -C 3 alkylene optionally substituted with C 1 -C 2 haloalkyl or 3 or 4-membered cycloalkyl; R 3 and R 4, together with the nitrogen atom to which they are attached, form: a 4 or 7-membered heteromonocyclic group optionally substituted with one to five substituents each independently selected from: C 1 -C 3 alkoxy, C 1 -C 3 alkyl, C 1 -C 3 haloalkoxy, C 1 -C 3 haloalkyl, 3 or 4-membered cycloalkoxy, 3 or 4-membered cycloalkyl, 3 or 4-membered heterocycloalkyl, carboxy, aryl, cyano, halo, and heteroaryl, wherein aryl and heteroaryl are optionally further substituted with one to five substituents each independently selected from C 1 -C 3 alkyl, C 1 -C 3 haloalkyl, and halo, or a 6, 7, 8, 9, or 10-membered heterobicyclic group, which is optionally substituted with one to five substituents each independently selected from: C 1 -C 3 alkoxy, C 1 -C 3 alkyl, C 1 -C 3 haloalkoxy, C 1 -C 3 haloalkyl, 3 or 4-membered cycloalkoxy, 3 or 4-membered cycloalkyl, 3 or 4-membered heterocycloalkyl, carboxy, aryl, cyano, halo, and heteroaryl, wherein aryl and heteroaryl are optionally further substituted with one to five substituents each independently selected from C 1 -C 3 alkyl, C 1 -C 3 haloalkyl, and halo; and R 5, R 6, R 7 and R 8 are each independently selected from H, C 1 -C 4 alkyl, C 1 -C 4 haloalkyl, and halo. W is N or CR 5; X is N or CR 6; Y is N or CR 7; and Z is N or CR 8; provided not more than two of W, X, Y, and Z are N; R 1 is selected from H and C 1 -C 3 alkyl; R 2 is C 2 -C 3 alkylene optionally substituted with C 1 -C 2 haloalkyl or 3 or 4-membered cycloalkyl; R 3 and R 4, together with the nitrogen atom to which they are attached, form: a 4 or 7-membered heteromonocyclic group optionally substituted with one to five substituents each independently selected from: C 1 -C 3 alkoxy, C 1 -C 3 alkyl, C 1 -C 3 haloalkoxy, C 1 -C 3 haloalkyl, 3 or 4-membered cycloalkoxy, 3 or 4-membered cycloalkyl, 3 or 4-membered heterocycloalkyl, carboxy, aryl, cyano, halo, and heteroaryl, wherein aryl and heteroaryl are optionally further substituted with one to five substituents each independently selected from C 1 -C 3 alkyl, C 1 -C 3 haloalkyl, and halo, or a 6, 7, 8, 9, or 10-membered heterobicyclic group, which is optionally substituted with one to five substituents each independently selected from: C 1 -C 3 alkoxy, C 1 -C 3 alkyl, C 1 -C 3 haloalkoxy, C 1 -C 3 haloalkyl, 3 or 4-membered cycloalkoxy, 3 or 4-membered cycloalkyl, 3 or 4-membered heterocycloalkyl, carboxy, aryl, cyano, halo, and heteroaryl, wherein aryl and heteroaryl are optionally further substituted with one to five substituents each independently selected from C 1 -C 3 alkyl, C 1 -C 3 haloalkyl, and halo; and a 4 or 7-membered heteromonocyclic group optionally substituted with one to five substituents each independently selected from: C 1 -C 3 alkoxy, C 1 -C 3 alkyl, C 1 -C 3 haloalkoxy, C 1 -C 3 haloalkyl, 3 or 4-membered cycloalkoxy, 3 or 4-membered cycloalkyl, 3 or 4-membered heterocycloalkyl, carboxy, aryl, cyano, halo, and heteroaryl, wherein aryl and heteroaryl are optionally further substituted with one to five substituents each independently selected from C 1 -C 3 alkyl, C 1 -C 3 haloalkyl, and halo, or a 6, 7, 8, 9, or 10-membered heterobicyclic group, which is optionally substituted with one to five substituents each independently selected from: C 1 -C 3 alkoxy, C 1 -C 3 alkyl, C 1 -C 3 haloalkoxy, C 1 -C 3 haloalkyl, 3 or 4-membered cycloalkoxy, 3 or 4-membered cycloalkyl, 3 or 4-membered heterocycloalkyl, carboxy, aryl, cyano, halo, and heteroaryl, wherein aryl and heteroaryl are optionally further substituted with one to five substituents each independently selected from C 1 -C 3 alkyl, C 1 -C 3 haloalkyl, and halo; and R 5, R 6, R 7 and R 8 are each independently selected from H, C 1 -C 4 alkyl, C 1 -C 4 haloalkyl, and halo.