Inhibitors of the glycine transporter 1

A compound of formula (I): wherein: X is -CH; R1 and R2 are, independently, hydrogen or alkyl; R3 and R4 are, independently, hydrogen, alkyl, haloalkyl, alkoxy or haloalkoxy; n1 is 0 or 1 and n2 is 1 or 2; and R5 is -NAr1Ar2, wherein Ar1 and Ar2 are independently aryl, heteroaryl. cycloalkyl or heterocyclyl wherein each of the rings mentioned above are optionally substituted by Ra, Rb or Rc wherein Ra is alkyl, halo, haloalkyl, haloalkoxy, alkylthio, cyano, alkoxy, amino, monosubstituted amino, disubstituted amino, sulfonyl, acyl , carboxy, alkoxycarbonyl, hydroxyalkyl, alkoxyalkyl, aminoalkyl, hydroxyalkoxy, alkoxyalkoxy, aminoalkoxy, aminosulfonyl, aminocarbonyl, or acylamino and Rb and Rc are independently selected from alkyl, halo, haloalkyl, haloalkoxy, alkylthio, cyano, alkoxy, amino, monosubstituted amino , disubstituted amino, sulfonyl, acyl, carboxy, alkoxycarbonyl. Hydroxyalkyl, alkoxyalkyl, aminoalkyl, hydroxyalkoxy, alkoxyalkoxy, aminoalkoxy, aminosulfonyl, aminocarbonyl, acylamino, aryl, heteroaryl, cycloalkyl or heterocyclyl and wherein the aromatic or alicyclic ring in Ra, Rb and Rc is optionally substituted with Rd, Re or Rf is independently selected from alkyl, halo, haloalkyl, haloalkoxy, alkylthio, cyano, alkoxy, amino, monosubstituted amino, disubstituted amino, sulfonyl, acyl, carboxy, alkoxycarbonyl, hydroxyalkyl, alkoxyalkyl, aminoalkyl. hydroxyalkoxy, alkoxyalkoxy, aminoalkoxy, aminosulfonyl, aminocarbonyl, or acylamino; or a pharmaceutically acceptable salt thereof.