A compound of Formula I wherein R 1 is selected from the group consisting of hydrogen, C 1 -C 6 alkyl, C 3 -C 7 cycloalkyl and C 3 -C 7 cycloalkylC 1 -C 3 alkyl; wherein the C 1 -C 6 alkyl, C 3 -C 7 cycloalkyl and C 3 -C 7 cycloalkylC 1 -C 3 alkyl are each optionally substituted with one to three independently selected halo, hydroxy or C 1 -C 3 alkoxy; R 2 is independently selected at each occurrence from the group consisting of halo, hydroxy and C 1 -C 3 alkyl; a is 0, 1, 2, 3 or 4; R 3 is selected from the group consisting of hydrogen, hydroxy, C 1 -C 6 alkyl and C 1 -C 6 alkoxy, wherein the C 1 -C 6 alkyl and C 1 -C 6 alkoxy are each optionally substituted with 1 to 3 fluoro; R 4 is hydrogen or C 1 -C 6 alkyl optionally substituted with one to three substituents independently selected from the group consisting of fluoro, C 1 -C 3 alkoxy and hydroxy; A is selected from the group consisting of C 6 -C 10 aryl and 5- to 10-membered heteroaryl; wherein the C 6 -C 10 aryl and 5- to 10-membered heteroaryl are optionally substituted with 1 to 3 R 6; R 5 is selected from the group consisting of halo, C 1 -C 6 alkyl, C 1 -C 6 alkoxy, C 1 -C 6 alkoxyC 1 -C 6 alkyl, C 3 -C 7 cycloalkyl, C 3 -C 7 cycloalkylC 1 -C 6 alkyl, C 3 -C 7 cycloalkoxy, phenoxy, 4- to 10-membered heterocycloalkyl and 4- to 10-membered heterocycloalkoxy; wherein the C 1 -C 6 alkyl, C 1 -C 6 alkoxy and C 1 -C 6 alkoxyC 1 -C 6 alkyl are optionally substituted with one to four independently selected halo or hydroxy; and wherein the C 3 -C 7 cycloalkyl, C 3 -C 7 cycloalkylC 1 -C 6 alkyl, C 3 -C 7 cycloalkoxy, phenoxy, 4-to 10-membered heterocycloalkyl and 4- to 10-membered heterocycloalkoxy are optionally substituted with one to four R 7; or R 4 and R 5 taken together are a C 1 -C 3 alkylene; R 6 is selected from the group consisting of halo, cyano, C 1 -C 6 alkyl optionally substituted with one to three fluoro, C 1 -C 6 alkoxy optionally substituted with one to three fluoro, and C 1 -C 6 alkoxyC 1 -C 6 alkyl; or R 4 and R 6 taken together are a C 1 -C 3 alkylene; or R 5 and R 6 when attached to adjacent carbons and taken together with the adjacent carbons to which they are attached form a fused 5- to 7-membered cycloalkyl ring or a 5- to 7-membered heterocycloalkyl ring, each of which is optionally substituted with one to four R 8; R 7 at each occurrence is independently selected from the group consisting of halo, hydroxy, C 1 -C 3 alkyl optionally substituted with one to three fluoro or C 1 -C 3 alkoxy, and C 1 -C 3 alkoxy optionally substituted with one to three fluoro; and R 8 at each occurrence is independently selected from halo, hydroxy, C 1 -C 3 alkyl optionally substituted with one to three fluoro, and C 1 -C 3 alkoxy optionally substituted with one to three fluoro; or a pharmaceutically acceptable salt thereof. R 1 is selected from the group consisting of hydrogen, C 1 -C 6 alkyl, C 3 -C 7 cycloalkyl and C 3 -C 7 cycloalkylC 1 -C 3 alkyl; wherein the C 1 -C 6 alkyl, C 3 -C 7 cycloalkyl and C 3 -C 7 cycloalkylC 1 -C 3 alkyl are each optionally substituted with one to three independently selected halo, hydroxy or C 1 -C 3 alkoxy; R 2 is independently selected at each occurrence from the group consisting of halo, hydroxy and C 1 -C 3 alkyl; a is 0, 1, 2, 3 or 4; R 3 is selected from the group consisting of hydrogen, hydroxy, C 1 -C 6 alkyl and C 1 -C 6 alkoxy, wherein the C 1 -C 6 alkyl and C 1 -C 6 alkoxy are each optionally substituted with 1 to 3 fluoro; R 4 is hydrogen or C 1 -C 6 alkyl optionally substituted with one to three substituents independently selected from the group consisting of fluoro, C 1 -C 3 alkoxy and hydroxy; A is selected from the group consisting of C 6 -C 10 aryl and 5- to 10-membered heteroaryl; wherein the C 6 -C 10 aryl and 5- to 10-membered heteroaryl are optionally substituted with 1 to 3 R 6; R 5 is selected from the group consisting of halo, C 1 -C 6 alkyl, C 1 -C 6 alkoxy, C 1 -C 6 alkoxyC 1 -C 6 alkyl, C 3 -C 7 cycloalkyl, C 3 -C 7 cycloalkylC 1 -C 6 alkyl, C 3 -C 7 cycloalkoxy, phenoxy, 4- to 10-membered heterocycloalkyl and 4- to 10-membered heterocycloalkoxy; wherein the C 1 -C 6 alkyl, C 1 -C 6 alkoxy and C 1 -C 6 alkoxyC 1 -C 6 alkyl are optionally substituted with one to four independently selected halo or hydroxy; and wherein the C 3 -C 7 cycloalkyl, C 3 -C 7 cycloalkylC 1 -C 6 alkyl, C 3 -C 7 cycloalkoxy, phenoxy, 4-to 10-membered heterocycloalkyl and 4- to 10-membered heterocycloalkoxy are optionally substituted with one to four R 7; or R 4 and R 5 taken together are a C 1 -C 3 alkylene; R 6 is selected from the group consisting of halo, cyano, C 1 -C 6 alkyl optionally substituted with one to three fluoro, C 1 -C 6 alkoxy optionally substituted with one to three fluoro, and C 1 -C 6 alkoxyC 1 -C 6 alkyl; or R 4 and R 6 taken together are a C 1 -C 3 alkylene; or R 5 and R 6 when attached to adjacent carbons and taken together with the adjacent carbons to which they are attached form a fused 5- to 7-membered cycloalkyl ring or a 5- to 7-membered heterocycloalkyl ring, each of which is optionally substituted with one to four R 8; R 7 at each occurrence is independently selected from the group consisting of halo, hydroxy, C 1 -C 3 alkyl optionally substituted with one to three fluoro or C 1 -C 3 alkoxy, and C 1 -C 3 alkoxy optionally substituted with one to three fluoro; and R 8 at each occurrence is independently selected from halo, hydroxy, C 1 -C 3 alkyl optionally substituted with one to three fluoro, and C 1 -C 3 alkoxy optionally substituted with one to three fluoro;