A compound having structural Formula I: or a pharmaceutically acceptable salt thereof wherein: X 1 is N; X 2 is CH; R 1 is CH 3 or CD 3; R 2 is: (a) -C 1-6 alkyl unsubstituted or substituted with (i) one to six of -F; (ii) -C 3-6 cycloalkyl unsubstituted or substituted with one to three of -F, or; (iii) phenyl unsubstituted or independently substituted at each occurrence with one to three of halo, -CN, -CH 3, or -OCH 3; (b) -C 3-6 cycloalkyl unsubstituted or substituted with one to three of -F, or; (c) phenyl unsubstituted or independently substituted at each occurrence with one to three of halo, -CN, -CH 3, or -OCH 3; R 2a is -H or -C 1-3 alkyl unsubstituted or substituted with one to three of -F; R 2b is -H or -C 1-3 alkyl unsubstituted or substituted with one to three of -F, or; R 2b is -H and R 2 and R 2a are joined together with the carbon to which they are both attached to represent: (a) -C 3-6 cycloalkyl unsubstituted or substituted with one to three of -F, or; (b) a 4 to 6 membered heterocycle comprised of carbons and one or two heteroatoms independently selected from N, O, or S, wherein the heterocycle is unsubstituted or independently substituted at each occurrence with one to three of halo, -CN, -CH 3, or -OCH 3; R 3 is -C 1-6 alkyl or -C 3-6 cycloalkyl; R 4 is (a) -C 1-6 alkyl; (b) -OC 1-6 alkyl; (c) -C 2-6 alkynyl; (d) -C 3-6 cycloalkyl; (e) -COO-C 1-6 alkyl; (f) -NHR a; (g) -NH-C -R a; (h) -C NHR a; (i) -CN; (j) phenyl unsubstituted or substituted with one to three substituents independently selected at each occurrence from halo,-C 1-6 alkyl, -OC 1-6 alkyl, -OH; or -CN, or; (k) phenyl substituted with a 5 or 6 membered heteroaryl comprised of carbon atoms, one to three of N, and zero or one of O, wherein the heteroaryl is unsubstituted or substituted with -C 1-3 alkyl; R a is (a) -H; (b) -C 1-6 alkyl unsubstituted or substituted with one or more substituents independently selected from -OH, one to three of -F, (c) -C 1-3 alkyl-C 3-6 cycloalkyl, (d) -C 3-6 cycloalkyl, or; (e) a 5 or 6 membered heteroaryl comprised of carbon atoms and one to three heteroatoms independently selected from N, O, and S, wherein the heteroaryl is unsubstituted or substituted with -C 1-3 alkyl, and; R 5 is NH 2. X 1 is N; X 2 is CH; R 1 is CH 3 or CD 3; R 2 is: (a) -C 1-6 alkyl unsubstituted or substituted with (i) one to six of -F; (ii) -C 3-6 cycloalkyl unsubstituted or substituted with one to three of -F, or; (iii) phenyl unsubstituted or independently substituted at each occurrence with one to three of halo, -CN, -CH 3, or -OCH 3; (b) -C 3-6 cycloalkyl unsubstituted or substituted with one to three of -F, or; (c) phenyl unsubstituted or independently substituted at each occurrence with one to three of halo, -CN, -CH 3, or -OCH 3; (a) -C 1-6 alkyl unsubstituted or substituted with (i) one to six of -F; (ii) -C 3-6 cycloalkyl unsubstituted or substituted with one to three of -F, or; (iii) phenyl unsubstituted or independently substituted at each occurrence with one to three of halo, -CN, -CH 3, or -OCH 3; (b) -C 3-6 cycloalkyl unsubstituted or substituted with one to three of -F, or; (c) phenyl unsubstituted or independently substituted at each occurrence with one to three of halo, -CN, -CH 3, or -OCH 3; R 2a is -H or -C 1-3 alkyl unsubstituted or substituted with one to three of -F; R 2b is -H or -C 1-3 alkyl unsubstituted or substituted with one to three of -F, or; R 2b is -H and R 2 and R 2a are joined together with the carbon to which they are both attached to represent: (a) -C 3-6 cycloalkyl unsubstituted or substituted with one to three of -F, or; (b) a 4 to 6 membered heterocycle comprised of carbons and one or two heteroatoms independently selected from N, O, or S, wherein the heterocycle is unsubstituted or independently substituted at each occurrence with one to three of halo, -CN, -CH 3, or -OCH 3; (a) -C 3-6 cycloalkyl unsubstituted or substituted with one to three of -F, or; (b) a 4 to 6 membered heterocycle comprised of carbons and one or two heteroatoms independently selected from N, O, or S, wherein the heterocycle is unsubstituted or independently substituted at each occurrence with one to three of halo, -CN, -CH 3, or -OCH 3; R 3 is -C 1-6 alkyl or -C 3-6 cycloalkyl; R 4 is (a) -C 1-6 alkyl; (b) -OC 1-6 alkyl; (c) -C 2-6 alkynyl; (d) -C 3-6 cycloalkyl; (e) -COO-C 1-6 alkyl; (f) -NHR a; (g) -NH-C -R a; (h) -C NHR a; (i) -CN; (j) phenyl unsubstituted or substituted with one to three substituents independently selected at each occurrence from halo,-C 1-6 alkyl, -OC 1-6 alkyl, -OH; or -CN, or; (k) phenyl substituted with a 5 or 6 membered heteroaryl comprised of carbon atoms, one to three of N, and zero or one of O, wherein the heteroaryl is unsubstituted or substituted with -C 1-3 alkyl; R a is (a) -H; (b) -C 1-6 alkyl unsubstituted or substituted with one or more substituents independently selected from -OH, one to three of -F, (c) -C 1-3 alkyl-C 3-6 cycloalkyl, (d) -C 3-6 cycloalkyl, or; (e) a 5 or 6 membered heteroaryl comprised of carbon atoms and one to three heteroatoms independently selected from N, O, and S, wherein the heteroaryl is unsubstituted or substituted with -C 1-3 alkyl, and; (a) -H; (b) -C 1-6 alkyl unsubstituted or substituted with one or more substituents independently selected from -OH, one to three of -F, (c) -C 1-3 alkyl-C 3-6 cycloalkyl, (d) -C 3-6 cycloalkyl, or; (e) a 5 or 6 membered heteroaryl comprised of carbon atoms and one to three heteroatoms independently selected from N, O, and S, wherein the heteroaryl is unsubstituted or substituted with -C 1-3 alkyl, and; R 5 is NH 2.