A compound of Formula Ia or Formula Ib: or a pharmaceutically acceptable salt, solvate, solvate of the salt, hydrate, a single stereoisomer, a mixture of stereoisomers, or a racemic mixture of stereoisomers thereof, wherein: Ar is phenyl, and is optionally substituted with 1 to 3 substituents independently selected from: (a) C 1 -C 6 alkyl, (b) C 3 -C 7 cycloalkyl, (c) heterocycle, (d) aryl, (e) heteroaryl, (f) halogen, (g) CN, (h) OR b, (i) N(R b)C(=O)R c, (j) C(=O)N(R b)(R c), (k) S(=O)mR b, (l) S(=O) 2 N(R b)(R c), (m) N(R b)S(=O) 2 R c, (n) SF 5; and (o) C 1 -C 6 haloalkyl W is selected from: (a) C(=O)OR 5, (b) C(=O)NHOH, (c) S(=O) 2 NHR b, (d) S(=O) 2 NHC(=O)R b, (e) NHC(=O)NHSO 2 R b, (f) 1 H -tetrazole, (g) 1,2,4-oxadiazol-5(4 H)one, (h) 1,2,4-thiadiazol-5(4 H)one, (i) 1,2,4-oxadiazole-5(4 H)-thione, (j) 1,2,4-triazole-5(4 H -one, (k) tetrazol-5(4 H)-one, and (l) C(=O)NHS(=O) 2 R b; X 1, X 2, X 3, X 4, and X 5 are each independently N or CR a, wherein not more than 2 of X 1, X 2, X 3, X 4, and X 5 are N; Y is a bond or -CH 2 -; R 3 and R 4 are independently selected from H, C 1 -C 3 alkyl, and C 1 -C 3 haloalkyl; R 5 is selected from (a) H, (b) C 1 -C 6 alkyl, (c) aryl, (d) aralkyl, (e) CH(R 7)OC(=O)R 8, (f) CH(R 7)OC(=O)OR 8, and (g) a (5-alkyl-2-oxo-1,3-dioxolen-4-yl)methyl group having the following formula: wherein R 6 is C 1 -C 6 alkyl; R 7 is hydrogen or C 1 -C 6 alkyl; R 8 is C 1 -C 6 alkyl or C 3 -C 6 cycloalkyl; R a is selected from: (a) H, (b) C 1 -C 6 alkyl, (c) halogen, (d) aryl, (e) OR b, (f) cyano, (g) heteroaryl, (h) C 3 -C 6 cycloalkyl, and (i) C 1 -C 6 haloalkyl; R b and R c are independently selected from: (a) H, (b) C 1 -C 6 alkyl, (c) aryl, (d) heteroaryl, (e) C 3 -C 6 cycloalkyl, and (f) C 1 -C 6 haloalkyl; or R b and R c taken together with the N to which they are both attached form a 3-to 6-membered heterocycle optionally having an additional heteroatom selected from N, O and S; m is 0, 1 or 2; and n is 1, 2 or 3. Ar is phenyl, and is optionally substituted with 1 to 3 substituents independently selected from: (a) C 1 -C 6 alkyl, (b) C 3 -C 7 cycloalkyl, (c) heterocycle, (d) aryl, (e) heteroaryl, (f) halogen, (g) CN, (h) OR b, (i) N(R b)C(=O)R c, (j) C(=O)N(R b)(R c), (k) S(=O)mR b, (l) S(=O) 2 N(R b)(R c), (m) N(R b)S(=O) 2 R c, (n) SF 5; and (o) C 1 -C 6 haloalkyl (a) C 1 -C 6 alkyl, (b) C 3 -C 7 cycloalkyl, (c) heterocycle, (d) aryl, (e) heteroaryl, (f) halogen, (g) CN, (h) OR b, (i) N(R b)C(=O)R c, (j) C(=O)N(R b)(R c), (k) S(=O)mR b, (l) S(=O) 2 N(R b)(R c), (m) N(R b)S(=O) 2 R c, (n) SF 5; and (o) C 1 -C 6 haloalkyl W is selected from: (a) C(=O)OR 5, (b) C(=O)NHOH, (c) S(=O) 2 NHR b, (d) S(=O) 2 NHC(=O)R b, (e) NHC(=O)NHSO 2 R b, (f) 1 H -tetrazole, (g) 1,2,4-oxadiazol-5(4 H)one, (h) 1,2,4-thiadiazol-5(4 H)one, (i) 1,2,4-oxadiazole-5(4 H)-thione, (j) 1,2,4-triazole-5(4 H -one, (k) tetrazol-5(4 H)-one, and (l) C(=O)NHS(=O) 2 R b; (a) C(=O)OR 5, (b) C(=O)NHOH, (c) S(=O) 2 NHR b, (d) S(=O) 2 NHC(=O)R b, (e) NHC(=O)NHSO 2 R b, (f) 1 H -tetrazole, (g) 1,2,4-oxadiazol-5(4 H)one, (h) 1,2,4-thiadiazol-5(4 H)one, (i) 1,2,4-oxadiazole-5(4 H)-thione, (j) 1,2,4-triazole-5(4 H -one, (k) tetrazol-5(4 H)-one, and (l) C(=O)NHS(=O) 2 R b; X 1, X 2, X 3, X 4, and X 5 are each independently N or CR a, wherein not more than 2 of X 1, X 2, X 3, X 4, and X 5 are N; Y is a bond or -CH 2 -; R 3 and R 4 are independently selected from H, C 1 -C 3 alkyl, and C 1 -C 3 haloalkyl; R 5 is selected from (a) H, (b) C 1 -C 6 alkyl, (c) aryl, (d) aralkyl, (e) CH(R 7)OC(=O)R 8, (f) CH(R 7)OC(=O)OR 8, and (g) a (5-alkyl-2-oxo-1,3-dioxolen-4-yl)methyl group having the following formula: wherein R 6 is C 1 -C 6 alkyl; (a) H, (b) C 1 -C 6 alkyl, (c) aryl, (d) aralkyl, (e) CH(R 7)OC(=O)R 8, (f) CH(R 7)OC(=O)OR 8, and (g) a (5-alkyl-2-oxo-1,3-dioxolen-4-yl)methyl group having the following formula: wherein R 6 is C 1 -C 6 alkyl; R 7 is hydrogen or C 1 -C 6 alkyl; R 8 is C 1 -C 6 alkyl or C 3 -C 6 cycloalkyl; R a is selected from: (a) H, (b) C 1 -C 6 alkyl, (c) halogen, (d) aryl, (e) OR b, (f) cyano, (g) heteroaryl, (h) C 3 -C 6 cycloalkyl, and (i) C 1 -C 6 haloalkyl; (a) H, (b) C 1 -C 6 alkyl, (c) halogen, (d) aryl, (e) OR b, (f) cyano, (g) heteroaryl, (h) C 3 -C 6 cycloalkyl, and (i) C 1 -C 6 haloalkyl; R b and R c are independently selected from: (a) H, (b) C 1 -C 6 alkyl, (c) aryl, (d) heteroaryl, (e) C 3 -C 6 cycloalkyl, and (f) C 1 -C 6 haloalkyl; or (a) H, (b) C 1 -C 6 alkyl, (c) aryl, (d) heteroaryl, (e) C 3 -C 6 cycloalkyl, and (f) C 1 -C 6 haloalkyl; or R b and R c taken together with the N to which they are both attached form a 3-to 6-membered heterocycle optionally having an additional heteroatom selected from N, O and S; m is 0, 1 or 2; and n is 1, 2 or 3.