N-hydroxyamidinoheterocycles as modulators of indoleamine 2,3-dioxygenase

1. A compound of Formula I:

or pharmaceutically acceptable salt thereof, wherein:

Q is C 1-6 alkyl substituted by phenyl, wherein said phenyl is substituted by 1, 2, or 3 substituents independently selected from halo and C 1-4 alkyl; or

Q is aryl optionally substituted by 1, 2, 3, 4, or 5 substituents independently selected from halo, C 1-6 alkyl, C 2-6 alkenyl, C 2-6 alkynyl, C 1-6 haloalkyl, C 1-6 hydroxyalkyl, C 1-6 cyanoalkyl, Cy 4 , —(C 1-4 alkyl)-Cy 4 , CN, NO 2 , OR a4 —(C 1-4 alkyl)-OR a4 , SR a4 , —(C 1-4 alkyl)-SR a4 , C(O)R b4 , —(C 1-4 alkyl)-C(O)R b4 , C(O)NR c4 R d4 , —(C 1-4 alkyl)-C(O)NR c4 R d4 , C(O)OR a4 , —(C 1-4 alkyl)-C(O)OR a4 , OC(O)R b4 , —(C 1-4 alkyl)-OC(O)R b4 , OC(O)NR c4 R d4 , —(C 1-4 alkyl)-OC(O)NR c4 R d4 , NR c4 R d4 , NR c4 C(O)R b4 , —(C 1-4 alkyl)-NR c4 COR b4 , NR c4 C(O)NR c4 R d4 , —(C 1-4 alkyl)-NR c4 ,C(O)NR c4 R d4 , NR c4 C(O)OR a4 , —(C 1-4 alkyl)-NR c4 C(O)OR a4 , C(═NR i4 )NR c4 R d4 , NR c4 C(═NR i4 )NR c4 R d4 , P(R f4 ) 2 , P(O)R e4 R f4 , P(O)OR e4 OR f4 , S(O)R b4 , —(C 1-4 alkyl)-S(O)R b4 , S(O)NR c4 R d4 , —(C 1-4 alkyl)-S(O)NR c4 R d4 , S(O) 2 R b4 , —(C 1-4 alkyl)-S(O) 2 R b4 , NR c4 S(O) 2 R b4 , —(C 1-4 alkyl)-NR(O) c4 S(O) 2 R b4 , S(O) 2 NR c4 R d4 , and —(C 1-4 alkyl)-S(O) 2 NR c4 R d4 ;

R 2 is halo, C 1-10 alkyl, C 2-10 alkenyl, C 2-10 alkynyl, C 1-6 haloalkyl, C 1-6 hydroxyalkyl, C 1-6 cyanoalkyl, pentahalosulfanyl, Cy 3 , CN, NO 2 , OR a3 , SR a3 , C(O)R b3 , C(O)NR c3 R d3 , C(O)OR a3 , OC(O)R b3 , OC(O)NR c3 Rd3, NR c3 R d3 , NR c3 C(O)R b3 , NR c3 C(O)NR c3 R d3 , NR c3 C(O)OR a3 , C(═NR i3 )NR c3 R d3 , NR c3 C(═NR i3 )NR c3 R d3 , P(R f3 ) 2 , S(O)R b3 , S(O)NR c3 R d3 , S(O) 2 R b3 , NR c3 S(O) 2 R b3 , or S(O) 2 NR c3 R d3 ; wherein said C 1-10 alkyl, C 2-10 alkenyl, or C 2-10 alkynyl, is optionally substituted with 1, 2, 3, 4, or 5 substituents independently selected from halo, C 1-10 alkyl, C 2-10 alkenyl, C 2-10 alkynyl, C 1-10 haloalkyl, C 1-10 hydroxyalkyl, C 1-10 cyanoalkyl, pentahalosulfanyl, Cy 3 , CN, NO 2 , OR a3 , SR a3 , C(O)R b3 , C(O)NR c3 R d3 , C(O)OR a3 , OC(O)R b3 , OC(O)NR c3 R d3 , NR c3 R d3 , NR c3 R d3 , NR c3 C(O)R b3 , NR c3 C(O)NR c3 R d3 , NR c3 C(O)OR a3 , C(═NR i3 )NR c3 R d3 , NR c3 C(═NR i3 )NR c3 R d3 , P(R f3 ) 2 , S(O)R b3 , S(O)NR c3 R d3 , S(O) 2 R b3 , NR c3 S(O) 2 R b3 , and S(O) 2 NR c3 R d3 ;

R 4 is selected from H, halo, C 1-4 alkyl, C 2-6 alkenyl, and C 2-6 alkynyl;

R 5 is H;

or R 2 and R 4 together with the atoms to which they are attached form an aryl, cycloalkyl, heteroaryl or 4-20 membered heterocycloalkyl ring, wherein said aryl, cycloalkyl, heteroaryl, or 4-20 membered heterocycloalkyl ring is optionally substituted with 1, 2, 3, 4, or 5 substituents independently selected from halo, C 1-6 alkyl, C 2-6 alkenyl, C 2-6 alkynyl, C 1-6 haloalkyl, C 1-6 hydroxyalkyl, C 1-6 cyanoalkyl, Cy 2 , CN, NO 2 , OR a2 , SR a2 , C(O)R b2 , C(O)NR c2 R d2 , C(O)OR a2 , OC(O)R b2 , OC(O)NR c2 R d2 , NR c2 R d2 , NR c2 C(O)R b2 , NR c2 C(O)NR c2 R d2 , NR c2 C(O)OR a2 , C(═NR i2 )NR c2 R d2 , NR c2 C(═NR i2 )NR c2 R d2 , P(R f2 ) 2 , P(OR e2 ) 2 , P(O)R e2 R f2 , P(O)OR e2 OR f2 , S(O)R b2 , S(O)NR c2 R d2 , S(O) 2 R b2 , NR c2 S(O) 2 R b2 , and S(O) 2 NR c2 R d2 , wherein said C 1-6 alkyl, C 2-6 alkenyl, or C 2-6 alkynyl, is optionally substituted with 1, 2, or 3 substituents independently selected from Cy 2 , CN, NO 2 , OR a2 , SR a2 , C(O)R b2 , C(O)NR c2 R d2 , C(O)OR a2 , OC(O)R b2 , OC(O)NR c2 R d2 , NR c2 R d2 , NR c2 C(O)R b2 , NR c2 C(O)NR c2 R d2 , NR c2 C(O)OR a2 , C(═NR i2 )NR c2R d2 NR c2 C(═NR i2 )NR c2 R d2 , P(R f2 ) 2 , P(OR e2 ) 2 , P(O)R e2 R f2 , P(O)OR e2 OR f2 , S(O)R b2 , S(O)NR c2 R d2 , S(O) 2 R b2 , NR c2 S(O) 2 R b2 , and S(O) 2 NR c2 R d2 ;

R a3 and R a4 are independently selected from H, C 1-6 alkyl, C 1-6 haloalkyl, C 2-6 alkenyl, C 2-6 alkynyl, Cy 5 , and Cy 5 —(C 1-6 alkyl)-, wherein said C 1-6 alkyl, C 2-6 alkenyl, or C 2-6 alkynyl is optionally substituted with 1, 2, 3, 4, or 5 substituents independently selected from halo, C 1-6 alkyl, C 2-6 alkenyl, C 2-6 alkynyl, C 1-6 haloalkyl, C 1-6 hydroxyalkyl, C 1-6 cyanoalkyl, Cy 5 , CN, NO 2 , OR a5 , SR a5 , C(O)R b5 , C(O)NR c5 R d5 , C(O)OR a5 , OC(O)R b5 , OC(O)NR c5 R d5 , NR c5 R d5 , NR c5 C(O)R b5 , NR c5 C(O)NR c5 R d5 , NR c5 C(O)OR a5 , C(═NR i5 )NR c5 R d5 , NR c5 C(═NR i5 )NR c5 R d5 , P(R f5 ) 2 , P(OR e5 ) 2 , P(O)R e5 R f5 , P(O)OR e5 OR f5 , S(O)R b5 , S(O)NR c5 R d5 , S(O) 2 R b5 , NR c5 S(O) 2 R b5 , and S(O) 2 NR c5 R d5 ;

R b3 and R b4 are independently selected from H, C 1-6 alkyl, C 1-6 haloalkyl, C 2-6 alkenyl, C 2-6 alkynyl, Cy 5 , and Cy 5 —(C 1-6 alkyl)-, wherein said C 1-6 alkyl, C 2-6 alkenyl, or C 2-6 alkynyl is optionally substituted with 1, 2, 3, 4, or 5 substituents independently selected from halo, C 1-6 alkyl, C 2-6 alkenyl, C 2-6 alkynyl, C 1-6 haloalkyl, C 1-6 hydroxyalkyl, C 1-6 cyanoalkyl, Cy 5 , CN, NO 2 , OR a5 , SR a5 , C(O)R b5 , C(O)NR c5 R d5 , C(O)OR a5 , OC(O)R b5 , OC(O)NR c5 R d5 , NR c5 R d5 , NR c5 C(O)R b5 , NR c5 C(O)NR c5 R d5 , NR c5 C(O)OR a5 , C(═NR i5 )NR c5 R d5 , NR c5 C(═NR i5 )NR c5 R d5 , P(R f5 ) 2 , P(OR e5 ) 2 , P(O)R e5 R f5 , P(O)OR e5 OR f5 , S(O)R b5 , S(O)NR c5 R d5 , S(O) 2 R b5 , NR c5 S(O) 2 R b5 , and S(O) 2 NR c5 R d5 ;

R c3 and R c4 are independently selected from H, C 1-6 alkyl, C 1-6 haloalkyl, C 2-6 alkenyl, C 2-6 alkynyl, C(O)R b5 , C(O)NR c5 R d5 , C(═NR i5 )NR c5 R d5 , Cy 5 , and Cy 5 —(C 1-6 alkyl)-, wherein said C 1-6 alkyl, C 2-6 alkenyl, or C 2-6 alkynyl is optionally substituted with 1, 2, 3, 4, or 5 substituents independently selected from halo, C 1-6 alkyl, C 2-6 alkenyl, C 2-6 alkynyl, C 1-6 haloalkyl, C 1-6 hydroxyalkyl, C 1-6 cyanoalkyl, Cy 5 , CN, NO 2 , OR a5 , SR a5 , C(O)R b5 , C(O)NR c5 R d5 , C(O)OR a5 , OC(O)R b5 , OC(O)NR c5 R d5 , NR c5 R d5 , NR c5 C(O)R b5 , NR c5 C(O)NR c5 R d5 , NR c5 C(O)OR a5 , C(═NR i5 )NR c5 R d5 , NR c5 C(═NR i5 )NR c5 R d5 , P(R f5 ) 2 , P(OR e5 ) 2 , P(O)R e5 R f5 , P(O)OR e5 OR f5 , S(O)R b5 , S(O)NR c5 R d5 , S(O) 2 R b5 , NR c5 S(O) 2 R b5 , and S(O) 2 NR c5 R d5 ;

R d3 and R d4 are independently selected from H, C 1-6 alkyl, C 1-6 haloalkyl, C 2-6 alkenyl, C 2-6 alkynyl, C(O)R b5 , C(O)NR c5 R d5 , C(═NR i5 )NR c5 R d5 , Cy 5 , and Cy 5 -(C 1-6 alkyl)-, wherein said C 1-6 alkyl, C 2-6 alkenyl, or C 2-6 alkynyl is optionally substituted with 1, 2, 3, 4, or 5 substituents independently selected from halo, C 1-6 alkyl, C 2-6 alkenyl, C 2-6 alkynyl, C 1-6 haloalkyl, C 1-6 hydroxyalkyl, C 1-6 cyanoalkyl, Cy 5 , CN, NO 2 , OR a5 , SR a5 , C(O)R b5 , C(O)NR c5 R d5 , C(O)OR a5 , OC(O)R b5 , OC(O)NR c5 R d5 , NR c5 R d5 , NR c5 C(O)R b5 , NR c5 C(O)NR c5 R d5 , NR c5 C(O)OR a5 , C(═NR i5 )NR c5 R d5 , NR c5 (═NR i5 )NR c5 R d5 , P(R f5 ) 2 , P(OR e5 ) 2 , P(O)R e5 R f5 , P(O)OR e5 OR f5 , S(O)R b5 , S(O)NR c5 R d5 , S(O) 2 R b5 , NR c5 S(O) 2 R b5 , and S(O) 2 NR c5 R d5 ;

or R c3 and R d3 together with the N atom to which they are attached form a 4-, 5-, 6- or 7- Membered heteroaryl or heterocycloalkyl group, each optionally substituted with 1, 2, 3, 4, or 5 substituents independently selected from halo, C 1-6 alkyl, C 2-6 alkenyl, C 2-6 alkynyl, C 1-6 haloalkyl, C 1-6 hydroxyalkyl, C 1-6 cyanoalkyl, Cy 5 , CN, NO 2 , OR a5 , SR a5 , C(O)R b5 , C(O)NR c5 R d5 , C(O)OR a5 , OC(O)R b5 , OC(O)NR c5 R d5 , NR c5 R d5 , NR c5 C(O)R b5 , NR c5 C(O)NR c5 R d5 , NR c5 C(O)OR a5 , C(═NR i5 )NR c5 R d5 , NR c5 C(═NR i5 )NR c5 R d5 , P(R f5 ) 2 , P(OR e5 ) 2 , P(O)R e5 R f5 , P(O)OR e5 OR f5 , S(O)R b5 , S(O)NR c5 R d5 , S(O) 2 R b5 , NR c5 S(O) 2 R b5 , and S(O) 2 NR c5 R d5 ;

or R c4 and R d4 together with the N atom to which they are attached form a 4-, 5-, 6- or 7- membered heteroaryl or heterocycloalkyl group, each optionally substituted with 1, 2, 3, 4, or 5 substituents independently selected from halo, C 1-6 alkyl, C 2-6 alkenyl, C 2-6 alkynyl, C 1-6 haloalkyl, C 1-6 hydroxyalkyl, C 1-6 cyanoalkyl, Cy 5 , CN, NO 2 , OR a5 , SR a5 , C(O)R b5 , C(O)NR c5 R d5 , C(O)OR a5 , OC(O)R b5 , OC(O)NR c5 R d5 , NR c5 R d5 , NR c5 C(O)R b5 , NR c5 C(O)NR c5 R d5 , NR c5 C(O)OR a5 , C(═NR i5 )NR c5 R d5 , NR c5 C(═NR i5 )NR c5 R d5 , P(R f5 ) 2 , P(OR e5 ) 2 , P(O)R e5 R f5 , P(O)OR e5 OR f5 , S(O)R b5 , S(O)NR c5 R d5 , S(O) 2 R b5 , NR c5 S(O) 2 R b5 , and S(O) 2 NR c5 R d5 ;

Cy 2 , Cy 3 , Cy 4 , and Cy 5 are independently selected from aryl, heteroaryl, cycloalkyl, and heterocycloalkyl, each optionally substituted by 1, 2, 3, 4 or 5 substituents selected from halo, C 1-4 alkyl, C 2-4 alkenyl, C 2-4 alkynyl, C 1-4 haloalkyl, pentahalosulfanyl, CN, NO 2 , OR a6 , SR a6 , C(O)R b6 , C(O)NR c6 R d6 , C(O)OR a6 , OC(O)R b6 , OC(O)NR c5 R d6 , NR c6 R d6 , NR c6 C(O)R b6 , NR c6 C(O)OR a6 , C(═NR i6 )NR c6 R d6 , NR c6 C(═NR i6 )NR c6 R d6 , P(R f6 ) 2 , P(OR e6 ) 2 , P(O)R e6 R f6 , S(O)R b6 , S(O)NR c6 R d6 , S(O) 2 R b6 , and S(O) 2 NR c6 R d6 ;

R a2 , R a5 , and R a6 are independently selected from H, C 1-10 alkyl, C 1-10 haloalkyl, C 2-10 alkenyl, C 2-10 alkynyl, aryl, cycloalkyl, heteroaryl, heterocycloalkyl, arylalkyl, heteroarylalkyl, cycloalkylalkyl, and heterocycloalkylalkyl, wherein said C 1-10 alkyl, C 1-10 haloalkyl, C 2-10 alkenyl, C 2-10 alkynyl, aryl, cycloalkyl, heteroaryl, heterocycloalkyl, arylalkyl, heteroarylalkyl, cycloalkylalkyl, or heterocycloalkylalkyl is optionally substituted with 1, 2, 3, 4, or 5 substituents independently selected from OH, amino, halo, C 1-6 alkyl, aryl, arylalkyl, heteroaryl, heteroarylalkyl, cycloalkyl, and heterocycloalkyl;

R b2 , R b5 , and R b6 are independently selected from H, C 1-10 alkyl, C 1-10 haloalkyl, C 2-10 alkenyl, C 2-10 alkynyl, aryl, cycloalkyl, heteroaryl, heterocycloalkyl, arylalkyl, heteroarylalkyl, cycloalkylalkyl, and heterocycloalkylalkyl, wherein said C 1-10 alkyl, C 1-10 haloalkyl, C 2-10 alkenyl, C 2-10 alkynyl, aryl, cycloalkyl, heteroaryl, heterocycloalkyl, arylalkyl, heteroarylalkyl, cycloalkylalkyl, or heterocycloalkylalkyl is optionally substituted with 1, 2, 3, 4, or 5 substituents indpendently selected from OH, amino, halo, C 1-6 alkyl, aryl, arylalkyl, heteroaryl, heteroarylalkyl, cycloalkyl, and heterocycloalkyl;

R c2 , R c5 , and R c6 are independently selected from H, C 1-10 alkyl, C 1-10 haloalkyl, C 2-10 alkenyl, C 2-10 alkynyl, aryl, cycloalkyl, heteroaryl, heterocycloalkyl, arylalkyl, heteroarylalkyl, cycloalkylalkyl, and heterocycloalkylalkyl, wherein said C 1-10 alkyl, C 1-10 haloalkyl, C 2-10 alkenyl, C 2-10 alkynyl, aryl, cycloalkyl, heteroaryl, heterocycloalkyl, arylalkyl, heteroarylalkyl, cycloalkylalkyl, or heterocycloalkylalkyl is optionally substituted with 1, 2, 3, 4, or 5 substituents independently selected from OH, amino, halo, C 1-6 alkyl, aryl, arylalkyl, heteroaryl, heteroarylalkyl, cycloalkyl, and heterocycloalkyl;

R d2 , R d5 , and R d6 are independently selected from H, C 1-10 alkyl, C 1-10 haloalkyl, C 2 - 10 alkenyl, C 2-10 alkynyl, aryl, cycloalkyl, heteroaryl, heterocycloalkyl, arylalkyl, heteroarylalkyl, cycloalkylalkyl, and heterocycloalkylalkyl, wherein said C 1-10 alkyl, C 1-10 haloalkyl, C 2-10 alkenyl, C 2-10 alkynyl, aryl, cycloalkyl, heteroaryl, heterocycloalkyl, arylalkyl, heteroarylalkyl, cycloalkylalkyl, or heterocycloalkylalkyl is optionally substituted with 1, 2, 3, 4, or 5 substituents independently selected from OH, amino, halo, C 1-6 alkyl, aryl, arylalkyl, heteroaryl, heteroarylalkyl, cycloalkyl, and heterocycloalkyl;

R e2 , R e5 , and R e6 are independently selected from H, C 1-10 alkyl, C 1-10 haloalkyl, C 2-10 alkenyl, C 2-10 alkynyl, aryl, cycloalkyl, heteroaryl, heterocycloalkyl, arylalkyl, heteroarylalkyl, cycloalkylalkyl, and heterocycloalkylalkyl, wherein said C 1-10 alkyl, C 1-10 haloalkyl, C 2-10 alkenyl, C 2-10 alkynyl, aryl, cycloalkyl, heteroaryl, heterocycloalkyl, arylalkyl, heteroarylalkyl, cycloalkylalkyl, or heterocycloalkylalkyl is optionally substituted with 1, 2, 3, 4, or 5 substituents independently selected from OH, amino, halo, C 1-6 alkyl, aryl, arylalkyl, heteroaryl, heteroarylalkyl, cycloalkyl, and heterocycloalkyl;

R f2 , R f3 , R f4 , R f5 , and R f6 are independently selected from H, C 1-10 alkyl, C 1-10 haloalkyl, C 2-10 alkenyl, C 2-10 alkynyl, aryl, cycloalkyl, heteroaryl, heterocycloalkyl, arylalkyl, heteroarylalkyl, cycloalkylalkyl, and heterocycloalkylalkyl, wherein said C 1-10 alkyl, C 1-10 haloalkyl, C 2-10 alkenyl, C 2-10 alkynyl, aryl, cycloalkyl, heteroaryl, heterocycloalkyl, arylalkyl, heteroarylalkyl, cycloalkylalkyl, or heterocycloalkylalkyl is optionally substituted with 1, 2, 3, 4, or 5 substituents independently selected from OH, amino, halo, C 1-6 alkyl, aryl, arylalkyl, heteroaryl, heteroarylalkyl, cycloalkyl, and heterocycloalkyl; and

R i2 , R i3 , R i4 , R i5 ,and R i6 are independently selected from H, C 1-10 alkyl, C 1-10 haloalkyl, C 2-10 alkenyl, C 2-10 alkynyl, aryl, cycloalkyl, heteroaryl, heterocycloalkyl, arylalkyl, heteroarylalkyl, cycloalkylalkyl, and heterocycloalkylalkyl, wherein said C 1-10 alkyl, C 1-10 haloalkyl, C 2-10 alkenyl, C 2-10 alkynyl, aryl, cycloalkyl, heteroaryl, heterocycloalkyl, arylalkyl, heteroarylalkyl, cycloalkylalkyl, or heterocycloalkylalkyl is optionally substituted with 1, 2, 3, 4, or 5 substituents independently selected from OH, amino, halo, C 1-6 alkyl, aryl, arylalkyl, heteroaryl, heteroarylalkyl, cycloalkyl, and heterocycloalkyl.

2. The compound of claim 1 , or pharmaceutically acceptable salt thereof, wherein Q is phenyl optionally substituted by 1, 2, 3, 4, or 5 substituents independently selected from halo, C 1-6 alkyl, C 2-6 alkenyl, C 2-6 alkynyl, C 1-6 haloalkyl, C 1-6 hydroxyalkyl, C 1-6 cyanoalkyl, CN, NO 2 , OR a4 , SR a4 , C(O)R b4 , C(O)NR c4 R d4 , C(O)OR a4 , OC(O)R b4 , OC(O)NR c4 R d4 , NR c4 R d4 , NR c4 C(O)R b4 , NR c4 C(O)NR c4 R d4 , NR c4 C(O)OR a4 , S(O)R b4 , S(O)NR c4 R d4 , S(O) 2 R b4 , NR c4 S(O) 2 R b4 , and S(O) 2 NR c4 R d4 .

3. The compound of claim 1 , or pharmaceutically acceptable salt thereof, wherein Q is phenyl optionally substituted by 1, 2, 3, 4, or 5 substituents independently selected from halo, C 1-6 alkyl, C 1-6 haloalkyl, and CN.

4. The compound of claim 1 , or pharmaceutically acceptable salt thereof, wherein Q is phenyl optionally substituted by 1, 2, 3, 4, or 5 substituents independently selected from halo and CN.

5. The compound of claim 1 , or pharmaceutically acceptable salt thereof, wherein R 2 is halo, C 1-10 alkyl, OR a3 , aryl, heteroaryl, or heterocycloalkyl, wherein said C 1-10 alkyl, aryl, heteroaryl, or heterocycloalkyl is optionally substituted with 1, 2, 3, 4, or 5 substituents independently selected from halo, C 1-10 alkyl, C 1-6 haloalkyl, OR a3 , and NR c3 R d3 .

6. The compound of claim 1 , or pharmaceutically acceptable salt thereof, wherein R 2 is halo.

7. The compound of claim 1 , or pharmaceutically acceptable salt thereof, wherein R 2 is C 1-10 alkyl.

8. The compound of claim 1 , or pharmaceutically acceptable salt thereof, wherein R 2 is NR c3 R d3 .

9. The compound of claim 1 , or pharmaceutically acceptable salt thereof, wherein R 2 is NH 2 .

10. The compound of claim 1 , or pharmaceutically acceptable salt thereof, wherein R 2 and R 4 together with the atoms to which they are attached form a phenyl group.

11. The compound of claim 1 selected from:

N-(3-chloro-4-fluorophenyl)-N′-hydroxy-3-(3-morpholin-1-ylpropoxy)isoxazole-5-carboximidamide;

N-(3-chloro-4-fluorophenyl)-N′-hydroxy-3-(3-(pyrrolidin-1-yl)propoxy)isoxazole-5-carboximidamide;

N-(3-chloro-4-fluorophenyl)-N′-hydroxy-3-morpholin-1-ylisoxazole-5-carboximidamide;

N-(3-chloro-4-fluorophenyl)-N′-hydroxy-3-phenylisoxazole-5-carboximidamide;

N-(3-chloro-4-fluorophenyl)-N′-hydroxy-3-(4-methoxyphenyl)isoxazole-5-carboximidamide;

N-(3-chloro-4-fluorophenyl)-N′-hydroxy-3-methoxyisoxazole-5-carboximidamide;

3-bromo-N-(3-bromophenyl)-N′-hydroxyisoxazole-5-carboximidamide;

3-bromo-N-(3-chloro-4-fluorophenye-N′-hydroxyisoxazole-5-carboximidamide;

N-(3-chloro-4-fluorophenyl)-N′-hydroxy-3-(3-(4-methylpiperazin-1-yl)propoxy)isoxazole-5-carboximidamide;

N-(3-chloro-4-fluorophenyl)-N′-hydroxy-3-methylisoxazole-5-carboximidamide;

4-chloro-N-(3-chloro-4-fluorophenyl)-N′-hydroxy-3-methylisoxazole-5-carboximidamide;

N-(3-chloro-4-fluorophenyl)-N′-hydroxy-2,1-benzisoxazole-3-carboximidamide;

3-bromo-N-(3-chlorobenzyl)-N-hydroxyisoxazole-5-carboximidamide;

3-bromo-N-(3-chloro-2-methylbenzyl)-N′-hydroxyisoxazole-5-carboximidamide;

3-bromo-N-(5-chloro-2-methylbenzyl)-N′-hydroxyisoxazole-5-carboximidamide;

3-bromo-N′-hydroxy-N-(2-methylbenzyl)isoxazole-5-carboximidamide;

N′-hydroxy-3-methyl-N-(2-methylbenzyl)isoxazole-5-carboximidamide;

N′-hydroxy-N-(2-methylbenzyl)-2,1-benzisoxazole-3-carboximidamide;

3-Amino-N-(5-chloro-2-methylbenzyl)-N′-hydroxyisoxazole-5-carboximidamide;

N-[5-[(5-chloro-2-methylbenzyeamino](hydroxyimino)methyl]isoxazol-3-ylacetamide;

N-(5-chloro-2-methylbenzyl)-N′-hydroxy-3-[(2-methoxyethy)amino]isoxazole-5-carboximidamide; and

3-amino-N-(3-bromo-4-fluorophenyl)-N′-hydroxyisoxazole-5-carboximidamide, or pharmaceutically acceptable salt thereof.

12. A composition comprising a compound of claim 1 , or pharmaceutically acceptable salt thereof, and a pharmaceutically acceptable carrier.

13. A method of inhibiting activity of indoleamine 2,3-dioxygenase comprising contacting said indoleamine 2,3-dioxygenase with a compound of claim 1 , or pharmaceutically acceptable salt thereof.

14. A method of treating breast cancer, wherein treating does not include preventing, in a patient in need thereof, comprising administering to said patient a therapeutically effective amount of a compound of claim 1 , or pharmaceutically acceptable salt thereof.

15. A method of treating melanoma, wherein treating does not include preventing, in a patient in need thereof, comprising administering to said patient a therapeutically effective amount of a compound of claim 1 , or pharmaceutically acceptable salt thereof.

16. A method of treating ovarian cancer, wherein treating does not include preventing, in a patient in need thereof, comprising administering to said patient a therapeutically effective amount of a compound of claim 1 , or pharmaceutically acceptable salt thereof.

17. The method of claim 14 , wherein the compound or salt is administered in combination with an anti-cancer agent.

18. The method of claim 17 , wherein the anti-cancer agent is an anti-CTLA4 antibody.

19. The method of claim 15 , wherein the compound or salt is administered in combination with an anti-cancer agent.

20. The method of claim 19 , wherein the anti-cancer agent is an anti-CTLA4 antibody.

21. The method of claim 16 , wherein the compound or salt is administered in combination with an anti-cancer agent.

22. The method of claim 21 , wherein the anti-cancer agent is an anti-CTLA4 antibody.