Substituted tetrahydroquinoline compounds as indoleamine 2,3-dioxygenase inhibitors

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

• wherein:
• X is selected from (1) a bond, (2) —O—, (3) —S— and (4) —NH—;
• each occurrence of R1 is independently selected from:
• (1) hydrogen, (2) halogen and (3) C1-6 alkyl;
• each of R2 and R3 is independently selected from:
• (1) hydrogen and (2) C1-6 alkyl;
• or alternatively, R2 and R3 together with the carbon to which they are attached form a C3-5 cycloalkyl;
• and
• R is selected from:
• (1) aryl,
• (2) heteroaryl and
• (3) C1-6 alkyl, optionally substituted with a C3-5 cycloalkyl;
• wherein each of the aryl of (1) and the heteroaryl of (2) is optionally substituted with one to four substituents independently selected from:
• (a) halogen,
• (b) —OH,
• (c) —CN,
• (d) C1-6 alkyl, optionally substituted with one to four substituents independently selected from (i) halogen and (ii) C3-6 cycloalkyl, and
• (e) —NRaRa, wherein each occurrence of Ra is independently selected from (i) hydrogen and (ii) C1-6 alkyl.