A compound of Formula: or a pharmaceutically acceptable salt thereof, wherein R 2 is hydrogen or C 1 - C 6 alkyl; R 3 is hydrogen, CN, C R 3a, C NHOH or 5-tetrazolyl; R 3a is OH, alkoxy or NHR 3b; R 3b is hydrogen, NH 2, OH or C 1 - C 6 alkyl; R 5a and R 5b are each independently hydrogen, C 1 - C 6 alkyl, or aralkyl which is optionally substituted with one to three substituents, each independently selected from Q 0 groups; where Q 0 is halo, cyano, nitro, NH 2, alkyl or alkoxy; R 6 is halo; in each instance, independently, R a and X 3 are selected from (i) or (ii) as follows: (i) R a is hydrogen or C 1 - C 6 alkyl; and X 3 is substituted or unsubstituted C 1 -C 3 alkylene, substituted or unsubstituted 3-6 membered cycloalkylene or substituted or unsubstituted 3-6 membered heterocyclylene, wherein the substituents when present are selected from one to four Q 2 groups; or (ii) R a and X 3 together with the nitrogen atom to which they are bonded, may form a 5 to 7 membered saturated or unsaturated ring optionally containing one or more O or S atoms, or one or more additional N atoms, in the ring; R b is -(CHR 7a) n R 7, -NR 7b R 7, -OR 7, -S r R 7, -NR 7b COY 1 R 7 or -Y 2 CONR 7b R 7; Y 1 is bond, O or NR 7b; Y 2 is bond or O; n is 0 or 1; r is an integer of 0 to 2; R 7 is alkyl, aryl, cycloalkyl, heterocyclyl, heteroaryl, fused heterocyclylaryl, or fused arylheterocyclyl, where R 7 is optionally substituted with one to five substituents, each independently selected from Q 1 groups; R 7a is hydrogen alkyl, aryl, cycloalkyl, heterocyclyl, heteroaryl, fused heterocyclylaryl, or fused arylheterocyclyl, where R 7a is optionally substituted with one to five substituents, each independently selected from Q 1 groups; R 7b is hydrogen, alkyl, aryl, heteroaryl, aralkyl, heteroaralkyl, or fused heterocyclylaryl, where R 7b is optionally substituted with one to five substituents, each independently selected from Q 1 groups; wherein Q 1 is halo, hydroxy, oxo, thioxo, cyano, nitro, azido, mercapto, formyl, hydroxycarbonyl, hydroxycarbonylalkyl, alkyl, haloalkyl, alkenyl, alkynyl, cycloalkyl, heterocyclyl, aryl, heteroaryl, aralkyl, heteroaralkyl, alkoxy, haloalkoxy, cycloalkoxy, heterocyclyloxy, aryloxy, heteroaryloxy, aralkyloxy, heretoaralkyloxy, alkylcarbonyl, arylcarbonyl, heteroarylcarbonyl, alkoxycarbonyl, aryloxycarbonyl, aralkyloxycarbonyl, unsubstituted or substituted aminocarbonyl, alkylcarbonyloxy, arylcarbonyloxy, aralkylcarbonyloxy, alkoxycarbonyloxy, aryloxycarbonyloxy, aralkyloxycarbonyloxy, unsubstituted or substituted aminocarbonyloxy, unsubstituted or substituted amino, alkylthio, cycloalkylthio, arylthio, heteroarylthio, aralkylthio, heteroaralkylthio, alkylsulfinyl, cycloalkylsulfinyl, arylsulfinyl, heteroarylsulfinyl, aralkylsulfinyl, heteroaralkylsulfinyl, alkylsulfonyl, cycloalkylsulfonyl, arylsulfonyl, heteroarylsulfonyl, aralkylsulfonyl, heteroaralkylsulfonyl, alkoxysulfonyl, aryloxysulfonyl, unsubstituted or substituted aminosulfonyl or hydroxysulfonyl; X 1 is O or NR 8; R 8 is hydrogen or C 1 - C 6 alkyl; X 2 is CH 2, O or NR 1; R 1 is hydrogen or C 1 - C 6 alkyl; A is substituted or unsubstituted C 1 -C 2 alkylene, wherein the substituents when present are selected from one to four Q 2 groups; where Q 2 is alkyl or haloalkyl; p is 0 or 1; and q is an integer of 0 to 2; wherein the term "cycloalkyl" refers to a saturated mono- or multicyclic system. (i) R a is hydrogen or C 1 - C 6 alkyl; and X 3 is substituted or unsubstituted C 1 -C 3 alkylene, substituted or unsubstituted 3-6 membered cycloalkylene or substituted or unsubstituted 3-6 membered heterocyclylene, wherein the substituents when present are selected from one to four Q 2 groups; or (ii) R a and X 3 together with the nitrogen atom to which they are bonded, may form a 5 to 7 membered saturated or unsaturated ring optionally containing one or more O or S atoms, or one or more additional N atoms, in the ring;