A compound of Formula I or a pharmaceutically acceptable salt thereof, wherein: X is: -O-Ar; -NR a -Ar; or -Ar; R 1 is: hydrogen; C 1-6 alkyl; halo; C 1-6 alkoxy; cyano; heteroaryl selected from furanyl, thienyl, pyrrolyl, pyrazolyl, imidazolyl, pyridinyl and pyrimidinyl, each of which may be unsubstituted or substituted once or twice with R b; -C -NHR c; -C -R c; or cyclopropyl which may be unsubstituted or substituted once or twice with R d; R 2 is: hydrogen; C 1-6 alkyl; C 1-6 alkoxy; halo; or halo-C 1-6 alkyl; R 3 is: hydrogen; C 1-6 alkyl; C 1-6 alkoxy; halo; or halo-C 1-6 alkyl; R 4 is: hydrogen; or C 1-6 alkyl; R 5 is: hydrogen; or C 1-6 alkyl; and R 6 is: hydrogen; C 1-6 alkyl; Ar is: phenyl or pyrazolyl, each of which may be unsubstituted or substituted one or two times with R e; R a is: hydrogen; or C 1-6 alkyl; each R b is independently: C 1-6 alkyl; halo; halo-C 1-6 alkyl; or cyclopropyl; R c is: C 1-6 alkyl; or halo-C 1-6 alkyl; R d is: C 1-6 alkyl; halo; halo-C 1-6 alkyl; hydroxy-C 1-6 alkyl; C 1-6 alkoxy-C 1-6 alkyl; or cyano; each R c is independently: C 1-6 alkyl; halo; halo-C 1-6 alkyl; -NH-C -R f; cyano; or cyclopropyl; and R f is furanyl, thienyl, pyrrolyl, pyrazolyl or imidazolyl; provided that 2-Benzyl-6-methyl-pyrido[1,2-a]pyrimidin-4-one; and 2-Benzyl-pyrido[1,2-a]pyrimidin-4-one; are excluded. X is: -O-Ar; -NR a -Ar; or -Ar; -O-Ar; -NR a -Ar; or -Ar; R 1 is: hydrogen; C 1-6 alkyl; halo; C 1-6 alkoxy; cyano; heteroaryl selected from furanyl, thienyl, pyrrolyl, pyrazolyl, imidazolyl, pyridinyl and pyrimidinyl, each of which may be unsubstituted or substituted once or twice with R b; -C -NHR c; -C -R c; or cyclopropyl which may be unsubstituted or substituted once or twice with R d; hydrogen; C 1-6 alkyl; halo; C 1-6 alkoxy; cyano; heteroaryl selected from furanyl, thienyl, pyrrolyl, pyrazolyl, imidazolyl, pyridinyl and pyrimidinyl, each of which may be unsubstituted or substituted once or twice with R b; -C -NHR c; -C -R c; or cyclopropyl which may be unsubstituted or substituted once or twice with R d; R 2 is: hydrogen; C 1-6 alkyl; C 1-6 alkoxy; halo; or halo-C 1-6 alkyl; hydrogen; C 1-6 alkyl; C 1-6 alkoxy; halo; or halo-C 1-6 alkyl; R 3 is: hydrogen; C 1-6 alkyl; C 1-6 alkoxy; halo; or halo-C 1-6 alkyl; hydrogen; C 1-6 alkyl; C 1-6 alkoxy; halo; or halo-C 1-6 alkyl; R 4 is: hydrogen; or C 1-6 alkyl; hydrogen; or C 1-6 alkyl; R 5 is: hydrogen; or C 1-6 alkyl; and hydrogen; or C 1-6 alkyl; and R 6 is: hydrogen; C 1-6 alkyl; hydrogen; C 1-6 alkyl; Ar is: phenyl or pyrazolyl, each of which may be unsubstituted or substituted one or two times with R e; R a is: hydrogen; or C 1-6 alkyl; hydrogen; or C 1-6 alkyl; each R b is independently: C 1-6 alkyl; halo; halo-C 1-6 alkyl; or cyclopropyl; C 1-6 alkyl; halo; halo-C 1-6 alkyl; or cyclopropyl; R c is: C 1-6 alkyl; or halo-C 1-6 alkyl; C 1-6 alkyl; or halo-C 1-6 alkyl; R d is: C 1-6 alkyl; halo; halo-C 1-6 alkyl; hydroxy-C 1-6 alkyl; C 1-6 alkoxy-C 1-6 alkyl; or cyano; C 1-6 alkyl; halo; halo-C 1-6 alkyl; hydroxy-C 1-6 alkyl; C 1-6 alkoxy-C 1-6 alkyl; or cyano; each R c is independently: C 1-6 alkyl; halo; halo-C 1-6 alkyl; -NH-C -R f; cyano; or cyclopropyl; and R f is furanyl, thienyl, pyrrolyl, pyrazolyl or imidazolyl; C 1-6 alkyl; halo; halo-C 1-6 alkyl; -NH-C -R f; cyano; or cyclopropyl; and R f is furanyl, thienyl, pyrrolyl, pyrazolyl or imidazolyl; provided that 2-Benzyl-6-methyl-pyrido[1,2-a]pyrimidin-4-one; and 2-Benzyl-pyrido[1,2-a]pyrimidin-4-one; are excluded. 2-Benzyl-6-methyl-pyrido[1,2-a]pyrimidin-4-one; and 2-Benzyl-pyrido[1,2-a]pyrimidin-4-one;