Substituted cyclobutylpyridine and cyclobutylpyrimidine compounds as indoleamine 2,3-dioxygenase (IDO) inhibitors

A compound of formula (I), or a pharmaceutically acceptable salt thereof:

• wherein:
• each occurrence of A is independently selected from —CH═ and N═;
• provided that at least one A group is —N═ and at least one A group is —CH═;
• L is selected from —NHC(O)— and —C(O)NH—;
• W is selected from —C(O)NH— and —NHC(O)—;
• R1 is selected from:
• (1) C1-6 alkyl,
• (2) —O—C1-6 alkyl,
• (3) C3-6 cycloalkyl,
• (4) aryl, and
• (5) heterocyclyl;
• wherein each of the C1-6 alkyl of (1) and (2) is optionally substituted with 1-3 substituents independently selected from (a) halogen and (b) C3-6 cycloalkyl;
• and
• wherein each of the C3-6 cycloalkyl of (3), aryl of (4), and heterocyclyl of (5) is optionally substituted with 1-3 substituents independently selected from (a) halogen, (b) —CN, (c) —O—C1-6 alkyl, and (d) C1-6 alkyl optionally substituted with 1-3 halogens;
• R2 is selected from:
• (1) C1-6 alkyl,
• (2) C3-6 cycloalkyl,
• (3) aryl, and
• (4) heterocyclyl;
• wherein the C1-6 alkyl of (1) is optionally substituted with 1-3 substituents independently selected from (a) halogen and (b) C3-6 cycloalkyl;
• and
• wherein each of the C3-6 cycloalkyl of (2), aryl of (3), and heterocyclyl of (4) is optionally substituted with 1-3 substituents independently selected from (a) halogen, (b) —CN, and (c) C1-6 alkyl optionally substituted with 1-3 halogens;
• R3 is selected from H, halogen, —OH, and C1-6 alkyl optionally substituted with —OH;
• and each of R4 and R5 is independently selected from H, halogen, and C1-6 alkyl.