TYK2 inhibitors and uses thereof

1. A compound of formula XX:

or a pharmaceutically acceptable salt thereof, wherein:

R 3 is —C(O)NH 2 , —C(O)NHR 3A , —C(O)N(R 3A ) 2 , —C(O)OR, —C(O)NHOR, or a 5-6 membered monocyclic heteroaryl ring having 1-4 heteroatoms independently selected from nitrogen, oxygen, and sulfur, wherein said ring is substituted with m instances of R 3B ;

R 6 is hydrogen, R A , or R B ;

R 7 is hydrogen, halogen, —NH 2 , —NHR 7A , or —NHC(O)R 7A ;

or R 6 and R 7 are taken together with their intervening atoms to form a 4-7 membered partially unsaturated, or heteroaryl ring having 0-3 heteroatoms independently selected from nitrogen, oxygen, and sulfur; wherein said ring is substituted by p instances of R C ;

R 3A , R 3B , and R 7A are each independently R B , and are each substituted by q instances of R C , wherein two R C substituents on the same carbon are optionally taken together to form a 3-6 membered saturated or partially unsaturated spiro-fused heterocyclic ring having 1-4 heteroatoms independently selected from nitrogen, oxygen, and sulfur, or wherein two R C substituents on adjacent carbons are optionally taken together to form a 3-6 membered saturated or partially unsaturated fused heterocyclic ring having 1-4 heteroatoms independently selected from nitrogen, oxygen, and sulfur;

each instance of R A is independently oxo, halogen, —CN, —NO 2 , —OR, —SR, —NR 2 , —S(O) 2 R, —S(O) 2 NR 2 , —S(O)R, —S(O)NR 2 , —C(O)R, —C(O)OR, —C(O)NR 2 , —C(O)N(R)OR, —OC(O)R, —OC(O)NR 2 , —N(R)C(O)OR, —N(R)C(O)R, —N(R)C(O)NR 2 , —N(R)C(NR)NR 2 , —N(R)S(O) 2 NR 2 , or —N(R)S(O) 2 R;

each instance of R B is independently C 1-6 aliphatic, phenyl, a 5-6 membered monocyclic heteroaryl ring having 1-4 heteroatoms independently selected from nitrogen, oxygen, and sulfur; an 8-10 membered bicyclic heteroaryl ring having 1-4 heteroatoms independently selected from nitrogen, oxygen, and sulfur; a 3-7 membered saturated or partially unsaturated carbocyclic ring, a 3-7 membered saturated or partially unsaturated monocyclic heterocyclic ring having 1-2 heteroatoms independently selected from nitrogen, oxygen, and sulfur; or a 7-12 membered saturated or partially unsaturated bicyclic heterocyclic ring having 1-4 heteroatoms independently selected from nitrogen, oxygen, and sulfur;

each instance of R C is independently oxo, halogen, —CN, —NO 2 , —OR, —SR, —NR 2 , —S(O) 2 R, —S(O) 2 NR 2 , —S(O)R, —S(O)NR 2 , —C(O)R, —C(O)OR, —C(O)NR 2 , —C(O)N(R)OR, —OC(O)R, —OC(O)NR 2 , —N(R)C(O)OR, —N(R)C(O)R, —N(R)C(O)NR 2 , —N(R)C(NR)NR 2 , —N(R)S(O) 2 NR 2 , or —N(R)S(O) 2 R or an optionally substituted group selected from C 1-6 aliphatic, phenyl, a 3-7 membered saturated or partially unsaturated heterocyclic ring having 1-2 heteroatoms independently selected from nitrogen, oxygen, and sulfur, and a 5-6 membered heteroaryl ring having 1-4 heteroatoms independently selected from nitrogen, oxygen, and sulfur, wherein two optional substituents on the same carbon are optionally taken together to form a 3-6 membered saturated or partially unsaturated spiro-fused heterocyclic ring having 1-4 heteroatoms independently selected from nitrogen, oxygen, and sulfur, or wherein two optional substituents on adjacent carbons are optionally taken together to form a 3-6 membered saturated or partially unsaturated fused heterocyclic ring having 1-4 heteroatoms independently selected from nitrogen, oxygen, and sulfur;

each R is independently hydrogen, or an optionally substituted group selected from C 1-6 aliphatic, phenyl, a 3-7 membered saturated or partially unsaturated heterocyclic having 1-2 heteroatoms independently selected from nitrogen, oxygen, and sulfur, and a 5-6 membered heteroaryl ring having 1-4 heteroatoms independently selected from nitrogen, oxygen, and sulfur, or:

two R groups on the same nitrogen are taken together with their intervening atoms to form a 4-7 membered saturated, partially unsaturated, or heteroaryl ring having 0-3 heteroatoms, in addition to the nitrogen, independently selected from nitrogen, oxygen, and sulfur;

wherein each hydrogen bound to carbon can be optionally and independently replaced by deuterium; and

each instance of m, p, q, and r is independently 0, 1, 2, 3, or .

2. The compound of claim 1 wherein R 7 is —NH 2 or —NHR 7A , or a pharmaceutically acceptable salt thereof.

3. The compound of claim 2 wherein each of R 3A and R 7A is independently R B , and is substituted by q instances of R C , provided that neither of R 3A or R 7A is phenyl.

4. The compound of claim 3 wherein R 7A is C 1-6 aliphatic.

5. The compound of claim 4 wherein R 7A is methyl.

6. The compound of claim 1 , wherein R 3 is selected from

7. The compound of claim 1 , wherein R is selected from

8. The compound of claim 1 , wherein R 3 is selected from

9. The compound of claim 8 , wherein R 3 is selected from

10. The compound of claim 1 , wherein R 3 is selected from

11. The compound of claim 1 , wherein R 6 is selected from hydrogen and methyl.

12. The compound of claim 1 , wherein R is selected from —NH 2 , —NHMe, —NHCD 3 ,

13. The compound of claim 1 , wherein R C is selected from

14. The compound of claim 1 , wherein m is 0, 1, 2, or 3.

15. The compound of claim 1 , wherein p is 0, 1, 2, or 3.

16. The compound of claim 1 , wherein q is 0, 1, 2, or 3.

17. The compound of claim 1 , wherein r is 0, 1, 2, or 3.

18. A compound selected from:

or a pharmaceutically acceptable salt thereof.

19. A pharmaceutical composition comprising a compound according to claim 1 , or a pharmaceutically acceptable salt thereof, and a pharmaceutically acceptable carrier, adjuvant, or vehicle.