A compound of the Formula or a pharmaceutically acceptable salt thereof, wherein X is N or O; B is a 5- to 10-membered mono- or bicyclic heteroaryl optionally containing 1 heteroatom in addition to the illustrated X atom, selected from the group consisting of N, O, and S; wherein B is unsubstituted or substituted by one to three R 3 moieties, wherein each R 3 moiety is independently selected from the group consisting of C 1 -C 3 alkyl, C 1 -C 3 alkoxy, C 1 -C 3 fluoroalkyl, C 1 -C 3 hydroxyalkyl, di(C 1 -C 3 alkyl)sulfonium, halo, hydroxy, amino, (C 1 -C 3 alkyl)amino, di(C 1 -C 3 alkyl)amino, -N SO 2 -(C 1 -C 3 alkyl), -CO 2 H, -C NH 2, -C N (C 1 -C 3 alkyl), -C N (C 1 -C 3 alkyl) 2, -CH 2 O-(C 1 -C 4 alkylene)-OH, phenyl, methyl pyrazolyl, pyridyl, and -CH 2 CH 2 -pyrrolidon-2-yl; or two R 3 moieties when substituted on adjacent carbon atoms of B, together with their attached carbon atoms, form a dioxanyl or dioxolanyl ring; A is selected from the group consisting of: (a) wherein Y is -CH 2 -, -S 2 -, or -O-; R 11 and R 12 are independently H or F; and the subscript n is 1 or 2; the subscript n' is 0 or 1; or (b) wherein R a and R b are independently H, C 1 -C 3 alkyl, or (C 1 -C 3 alkoxy)methyl; R c is H, C 1 -C 6 alkyl, C 1 -C 3 fluoroalkyl, C 3 -C 6 cycloalkyl, -(CH 2) r OR 13, -C NH 2, -C N (C 1 -C 3 alkyl), -C N(C 1 -C 3 alkyl) 2, -(CH 2) r S t R 14, -(CH 2) r -phenyl, or -(CH 2) r N C -(C 1 -C 3 alkyl); R 13 is H or C 1 -C 3 alkyl; and R 14 is C 1 -C 3 alkyl; the subscript r is 1 or 2; the subscript t is 0, 1, or 2; R d is H or C 1 -C 3 alkyl. X is N or O; B is a 5- to 10-membered mono- or bicyclic heteroaryl optionally containing 1 heteroatom in addition to the illustrated X atom, selected from the group consisting of N, O, and S; wherein B is unsubstituted or substituted by one to three R 3 moieties, wherein each R 3 moiety is independently selected from the group consisting of C 1 -C 3 alkyl, C 1 -C 3 alkoxy, C 1 -C 3 fluoroalkyl, C 1 -C 3 hydroxyalkyl, di(C 1 -C 3 alkyl)sulfonium, halo, hydroxy, amino, (C 1 -C 3 alkyl)amino, di(C 1 -C 3 alkyl)amino, -N SO 2 -(C 1 -C 3 alkyl), -CO 2 H, -C NH 2, -C N (C 1 -C 3 alkyl), -C N (C 1 -C 3 alkyl) 2, -CH 2 O-(C 1 -C 4 alkylene)-OH, phenyl, methyl pyrazolyl, pyridyl, and -CH 2 CH 2 -pyrrolidon-2-yl; or two R 3 moieties when substituted on adjacent carbon atoms of B, together with their attached carbon atoms, form a dioxanyl or dioxolanyl ring; A is selected from the group consisting of: (a) wherein Y is -CH 2 -, -S 2 -, or -O-; R 11 and R 12 are independently H or F; and the subscript n is 1 or 2; the subscript n' is 0 or 1; or (b) wherein R a and R b are independently H, C 1 -C 3 alkyl, or (C 1 -C 3 alkoxy)methyl; R c is H, C 1 -C 6 alkyl, C 1 -C 3 fluoroalkyl, C 3 -C 6 cycloalkyl, -(CH 2) r OR 13, -C NH 2, -C N (C 1 -C 3 alkyl), -C N(C 1 -C 3 alkyl) 2, -(CH 2) r S t R 14, -(CH 2) r -phenyl, or -(CH 2) r N C -(C 1 -C 3 alkyl); R 13 is H or C 1 -C 3 alkyl; and R 14 is C 1 -C 3 alkyl; the subscript r is 1 or 2; the subscript t is 0, 1, or 2; R d is H or C 1 -C 3 alkyl. (a) wherein Y is -CH 2 -, -S 2 -, or -O-; R 11 and R 12 are independently H or F; and the subscript n is 1 or 2; the subscript n' is 0 or 1; or Y is -CH 2 -, -S 2 -, or -O-; R 11 and R 12 are independently H or F; and the subscript n is 1 or 2; the subscript n' is 0 or 1; or (b) wherein R a and R b are independently H, C 1 -C 3 alkyl, or (C 1 -C 3 alkoxy)methyl; R c is H, C 1 -C 6 alkyl, C 1 -C 3 fluoroalkyl, C 3 -C 6 cycloalkyl, -(CH 2) r OR 13, -C NH 2, -C N (C 1 -C 3 alkyl), -C N(C 1 -C 3 alkyl) 2, -(CH 2) r S t R 14, -(CH 2) r -phenyl, or -(CH 2) r N C -(C 1 -C 3 alkyl); R 13 is H or C 1 -C 3 alkyl; and R 14 is C 1 -C 3 alkyl; the subscript r is 1 or 2; the subscript t is 0, 1, or 2; R d is H or C 1 -C 3 alkyl. R a and R b are independently H, C 1 -C 3 alkyl, or (C 1 -C 3 alkoxy)methyl; R c is H, C 1 -C 6 alkyl, C 1 -C 3 fluoroalkyl, C 3 -C 6 cycloalkyl, -(CH 2) r OR 13, -C NH 2, -C N (C 1 -C 3 alkyl), -C N(C 1 -C 3 alkyl) 2, -(CH 2) r S t R 14, -(CH 2) r -phenyl, or -(CH 2) r N C -(C 1 -C 3 alkyl); R 13 is H or C 1 -C 3 alkyl; and R 14 is C 1 -C 3 alkyl; the subscript r is 1 or 2; the subscript t is 0, 1, or 2; R d is H or C 1 -C 3 alkyl.