Inhibitors of the kynurenine pathway

A compound of formula (I):

• wherein:
• X1 is CR1;
• X2 is CR2;
• X3 is N;
• X4 is CR4;
• Y is O,
• Z is NR5R6;
• R1, R2 and R4 are independently selected from the group consisting of H, optionally substituted C1-C6 alkyl, optionally substituted C2-C6 alkenyl, optionally substituted C2-C6 alkynyl, optionally substituted C1-C6 alkoxy, mono or bicyclic optionally substituted C6-C14 aryl, mono or bicycle optionally substituted heteroaryl, optionally substituted (aryl)alkyl, (alkoxy)carbonyl, (alkyl)amido, (alkyl)amino, optionally substituted mono or bicyclic cycloalkyl, optionally substituted mono or bicycle heterocyclyl, aminoalkyl, alkylcarboxyl, (alkyl)carboxyamido, optionally substituted (aryl)amino, hydroxyl, halogen, C1-C6 haloalkyl, optionally substituted heterocyclyl(alkyl)-, optionally substituted heteroaryl(alkyl), hydroxyalkyl, perfluoroalkyl, optionally substituted aryloxy, optionally substituted heteroaryloxy, optionally substituted C3-C8 cycloalkoxy, N(R7)2, CN, NO2, CO2H, CONRARB, S(O)nR7, and optionally substituted heterocyclyloxy having 1 to 2 heteroatoms selected from the group consisting of O, S(O)n, and NR7;
• n is 0 to 2;
• RA and RB are independently selected from the group consisting of H, optionally substituted C1-C6 alkyl, optionally substituted mono or bicyclic C6-C14 aryl, optionally substituted mono or bicyclic heteroaryl, optionally substituted (aryl)alkyl, optionally substituted mono or bicyclic C3-C8 cycloalkyl, optionally substituted mono or bicyclic heterocyclyl, C1-C6 haloalkyl, optionally substituted heterocyclyl(alakyl), optionally substituted heteroaryl(alkyl), hydroxyalkyl, and perfluoroalkyl;
• R5 is selected from the group consisting of optionally substituted C1-C6 alkyl, optionally substituted mono or bicyclic C6-C14 aryl, optionally substituted (aryl)alkyl, optionally substituted mono or bicyclic cycloalkyl, optionally substituted mono or bicyclic heterocyclyl, C1-C6 haloalkyl, optionally substituted heterocyclyl(alkyl), optionally substituted heteroaryl(alkyl), hydroxyalkyl, and perfluoroalkyl;
• R6 is H;
• and
• R7 is H, C1-C6 alkyl, mono or bicyclic C6-C14 aryl, mono or bicyclic heteroaryl, (aryl)alkyl, (alkoxy)carbonyl, (alkyl)amido, (alkyl)amino, mono or bicyclic cycloalkyl, mono or bicyclic heterocyclyl, alkylcarboxyl, heterocyclyl(alkyl), heteroaryl(alkyl), hydroxyalkyl, perfluoroalkyl, aryloxy, heteroaryloxy, C3-C6 cycloalkoxy, or heterocyclyloxy having 1 to 2 heteroatoms selected from the group consisting of O, S(O)n, and NRA;
• or a pharmaceutically acceptable salt thereof.