Antagonists of the mGlu receptor and uses thereof

A compound of formula (I)

• or a pharmaceutically acceptable salt or prodrug thereof, wherein
• R1 is selected from the group consisting of alkyl, aryl, cycloalkyl, heterocycle and heteroaryl;
• R2 is selected from the group consisting of hydrogen and alkyl,
• R3 is selected from the group consisting of hydrogen, alkoxyl, aryloxyl, cyano, halogen, heteroalkoxyl, and heteroaryloxyl;
• X1 is selected from the group consisting of —N—, —N+(O−)— and —C(R4)—;
• X2 is selected from the group consisting of —N—, —N+(O−)— and —C(R5)—;
• X3 is selected form the group consisting of S, O, and NH;
• X4 is selected from the group consisting of N and —C(R6)—;
• X5 is selected from the group consisting of —NRaRb and —N+(O−)RaRb;
• R4 and R5 are each independently selected from the group consisting of hydrogen, alkyl, haloalkyl, hydroxy, and hydroxyalkyl;
• R6 are each independently selected from the group consisting of hydrogen, alkyl, haloalkyl, hydroxy, and hydroxyalkyl;
• and
• Ra and Rb are each independently selected from the group consisting of hydrogen, alkyl, alkoxyalkyl, haloalkyl, hydroxyalkyl, arylalkyl, heteroarylalkyl and heterocyclealkyl, RcRdNalkyl, cyanoalkyl, and cycloalkyl, wherein Rc and Rd are independently selected from the group consisting of hydrogen and alkyl;
• alternatively, Ra and Rb taken together with the nitrogen to which they are attached form a heterocycle;
• with the proviso that
• if X1 is N, then X2 is —C(R5)—, and
• if X2 is N, then X1 is —C(R4)—;
• and
• the compound is not
• 9-Dimethylamino-3-(p-tolyl)-3H-5-thia-1,3,6-triazafluoren-4-one;
• 9-Dimethylamino-3-(p-methoxyphenyl)-3H-5-thia-1,3,6-triazafluoren-4-one;
• 9-Dimethylamino-3-(p-chlorophenyl)-3H-5-thia-1,3,6-triazafluoren-4-one;
• and
• 9-Dimethylamino-3-(p-phenyl)-3H-5-thia-1,3,6-triazafluoren-4-one.