A compound of formula: or a pharmaceutically acceptable salt thereof, wherein: X 1, X 2 and X 3 are each -CH=; R 1 is halo, hydroxyl, cyano, C 1-6 alkyl, C 1-6 alkenyl, C 1-6 haloalkyl, C 1-6 alkoxy, -O-C -C 1-6 alkyl, -C -O-C 1-6 alkyl, -C -NR 6 -C 1-6 alkyl, -NR 6 -C -C 1-6 alkyl, -C 1-6 alkyl-C -NR 6 -C 1-6 alkyl, -C 1-6 alkyl-NR 6 -C -C 1-6 alkyl, -C 1-6 alkyl-NR 6 -C -O-C 1-6 alkyl,-C 1-6 alkyl-C -O-C 1-6 alkyl, -O-C -NR 6 -C 1-6 alkyl, C 3-7 cycloalkyl, C 3-7 cycloalkylalkyl, aryl, heteroaryl, aralkyl, heteroaralkyl, heterocyclyl or heterocyclylalkyl, wherein each alkyl, alkenyl, alkoxy, cycloalkyl, aryl, heteroaryl and heterocyclyl is substituted with 0-3 occurrences of R 7; R 2 is halo, hydroxyl, C 1-6 alkyl, C 1-6 haloalkyl or C 1-6 alkoxy; or alternatively, R 1 and R 2 taken together with the carbon atom to which they are attached form a cycloalkyl or heterocyclyl substituted with 0-3 occurrences of R 7; R 3 is hydrogen; R 4 is absent; R 5 is cycloalkyl substituted with 0-3 occurrences of R 7, wherein cycloalkyl refers to a monocyclic, bicyclic, tricyclic, or tetracyclic carbon ring, wherein for a bicyclic, tricyclic, or tetracyclic carbon ring, the point of attachment is a fully or partially saturated bridged or non-bridged hydrocarbon ring, and the other ring(s) may be saturated, partially unsaturated, or aromatic ring(s) and optionally containing one or more heteroatoms selected from O, S or N; each R 6 is independently hydrogen or C 1-6 alkyl; each R 7 is independently halo, cyano, N(R 8) 2, -C -N(R 8) 2, hydroxyl, C 1-6 alkyl, C 1-6 alkoxy, C 3-7 cycloalkyl, aryl, aryloxy, heteroaryl, heteroaryloxy or heterocyclyl, wherein each alkyl, alkoxy, cycloalkyl, aryl, aryloxy, heteroaryl, heteroaryloxy or heterocyclyl is substituted with 0-3 occurrences of R 9; each R 8 is independently hydrogen, C 1-6 alkyl, C -C 1-6 alkyl, aryl, or benzyl; or alternatively, two R 8 groups taken together with the nitrogen to which they are attached form a heterocyclyl; and each R 9 is independently halo, C 1-6 alkyl, C 1-6 alkoxy or C 1-6 haloalkyl. X 1, X 2 and X 3 are each -CH=; R 1 is halo, hydroxyl, cyano, C 1-6 alkyl, C 1-6 alkenyl, C 1-6 haloalkyl, C 1-6 alkoxy, -O-C -C 1-6 alkyl, -C -O-C 1-6 alkyl, -C -NR 6 -C 1-6 alkyl, -NR 6 -C -C 1-6 alkyl, -C 1-6 alkyl-C -NR 6 -C 1-6 alkyl, -C 1-6 alkyl-NR 6 -C -C 1-6 alkyl, -C 1-6 alkyl-NR 6 -C -O-C 1-6 alkyl,-C 1-6 alkyl-C -O-C 1-6 alkyl, -O-C -NR 6 -C 1-6 alkyl, C 3-7 cycloalkyl, C 3-7 cycloalkylalkyl, aryl, heteroaryl, aralkyl, heteroaralkyl, heterocyclyl or heterocyclylalkyl, wherein each alkyl, alkenyl, alkoxy, cycloalkyl, aryl, heteroaryl and heterocyclyl is substituted with 0-3 occurrences of R 7; R 2 is halo, hydroxyl, C 1-6 alkyl, C 1-6 haloalkyl or C 1-6 alkoxy; or alternatively, R 1 and R 2 taken together with the carbon atom to which they are attached form a cycloalkyl or heterocyclyl substituted with 0-3 occurrences of R 7; R 3 is hydrogen; R 4 is absent; R 5 is cycloalkyl substituted with 0-3 occurrences of R 7, wherein cycloalkyl refers to a monocyclic, bicyclic, tricyclic, or tetracyclic carbon ring, wherein for a bicyclic, tricyclic, or tetracyclic carbon ring, the point of attachment is a fully or partially saturated bridged or non-bridged hydrocarbon ring, and the other ring(s) may be saturated, partially unsaturated, or aromatic ring(s) and optionally containing one or more heteroatoms selected from O, S or N; each R 6 is independently hydrogen or C 1-6 alkyl; each R 7 is independently halo, cyano, N(R 8) 2, -C -N(R 8) 2, hydroxyl, C 1-6 alkyl, C 1-6 alkoxy, C 3-7 cycloalkyl, aryl, aryloxy, heteroaryl, heteroaryloxy or heterocyclyl, wherein each alkyl, alkoxy, cycloalkyl, aryl, aryloxy, heteroaryl, heteroaryloxy or heterocyclyl is substituted with 0-3 occurrences of R 9; each R 8 is independently hydrogen, C 1-6 alkyl, C -C 1-6 alkyl, aryl, or benzyl; or alternatively, two R 8 groups taken together with the nitrogen to which they are attached form a heterocyclyl; and each R 9 is independently halo, C 1-6 alkyl, C 1-6 alkoxy or C 1-6 haloalkyl.