Melanocortin ligands and methods of use thereof

1. A compound of formula (I):

R 1 —C(═O)—W—X—Y—Z—N(R 2 ) 2   (I)

wherein

R 1 is H, (C 1 -C 6 )cycloalkyl or (C 1 -C 4 )alkyl, optionally substituted with cycloalkyl;

each R 2 is independently H or (C 1 -C 6 )alkyl;

W is an amino acid;

X is L-arginine or L-glutamine and Y is D-phenylalanine, wherein the phenyl ring is substituted with one or more halo groups and the phenyl ring is further optionally substituted with one or more (C 1 -C 4 )alkyl, —O(C 1 -C 4 )alkyl, (C 1 -C 4 )haloalkyl, or —O(C 1 -C 4 )haloalkyl; or X is L-phenylalanine, wherein the phenyl ring is substituted with one or more halo groups and the phenyl ring is further optionally substituted with one or more (C 1 -C 4 )alkyl, —O(C 1 -C 4 )alkyl, (C 1 -C 4 )haloalkyl, or —O(C 1 -C 4 )haloalkyl, and Y is D-arginine or D-glutamine; and

Z is an amino acid;

or a salt thereof.

2. A compound of claim 1 , which is a compound of formula (Ia):

R 1 —C(═O)—W—X—Y—Z—N(R 2 ) 2   (Ia)

wherein X is L-arginine or L-glutamine and Y is D-phenylalanine, wherein the phenyl ring is substituted with one or more halo groups and the phenyl ring is further optionally substituted with one or more (C 1 -C 4 )alkyl, —O(C 1 -C 4 )alkyl, (C 1 -C 4 )haloalkyl, or —O(C 1 -C 4 )haloalkyl;

or a salt thereof.

3. The compound of claim 2 , wherein X is L-arginine and Y is D-phenylalanine, wherein the phenyl ring is substituted with one or more halo groups.

4. The compound of claim 2 , wherein X is L-glutamine and Y is D-phenylalanine, wherein the phenyl ring is substituted with one or more halo groups.

5. A compound of claim 1 , which is a compound of formula (Ib):

R 1 —C(═O)—W—X—Y—Z—N(R 2 ) 2   (Ib)

wherein X is L-phenylalanine, wherein the phenyl ring is substituted with one or more halo groups and the phenyl ring is further optionally substituted with one or more (C 1 -C 4 )alkyl, —O(C 1 -C 4 )alkyl, (C 1 -C 4 )haloalkyl, or —O(C 1 -C 4 )haloalkyl, and Y is D-arginine or D-glutamine;

or a salt thereof.

6. The compound of claim 5 , wherein X is L-phenylalanine, wherein the phenyl ring is substituted with one or more halo groups, and Y is D-arginine.

7. The compound of claim 1 , wherein R 1 is H and/or each R 2 is H.

8. The compound of claim 1 , wherein W is an amino acid selected from the group consisting of L-Ala, L-Asp, L-Glu, L-Phe, L-Gly, L-His, L-Ile, L-Lys, L-Leu, L-Met, L-Asn, L-Pro, L-Gln, L-Arg, L-Ser, L-Thr, L-Val, L-Trp, L-Tyr, D-Ala, D-Asp, D-Glu, D-Phe, D-His, D-Ile, D-Lys, D-Leu, D-Met, D-Asn, D-Pro, D-Gln, D-Arg, D-Ser, D-Thr, D-Val, D-Trp, D-Tyr, L-Nle, D-Nle, L-Cha, D-Cha, L-PyrAla, D-PyrAla, L-ThiAla, D-ThiAla, L-Tic, D-Tic, (pCl)L-Phe, (pCl)D-Phe, (pI)L-Phe, (pI)D-Phe, (pNO 2 )L-Phe, (pNO 2 )D-Phe, 2-L-Nal, 2-D-Nal, β-Ala, ε-Aminocaproic acid, D-Met[O 2 ], L-Met[O 2 ], L-dehydPro, D-dehydPro, L-(3I)Tyr and D-(3I)Tyr.

9. The compound of claim 1 , wherein W is L-His, L-Arg, D-Tic, L-Val or D-Phe.

10. The compound of claim 1 , wherein Z is an amino acid selected from the group consisting of L-Ala, L-Asp, L-Glu, L-Phe, L-Gly, L-His, L-Ile, L-Lys, L-Leu, L-Met, L-Asn, L-Pro, L-Gln, L-Arg, L-Ser, L-Thr, L-Val, L-Trp, L-Tyr, D-Ala, D-Asp, D-Glu, D-Phe, D-His, D-Ile, D-Lys, D-Leu, D-Met, D-Asn, D-Pro, D-Gln, D-Arg, D-Ser, D-Thr, D-Val, D-Trp, D-Tyr, L-Nle, D-Nle, L-Cha, D-Cha, L-PyrAla, D-PyrAla, L-ThiAla, D-ThiAla, L-Tic, D-Tic, (pCl)L-Phe, (pCl)D-Phe, (pI)L-Phe, (pI)D-Phe, (pNO 2 )L-Phe, (pNO 2 )D-Phe, 2-L-Nal, 2-D-Nal, β-Ala, ε-Aminocaproic acid, D-Met[O 2 ], L-Met[O 2 ], L-dehydPro, D-dehydPro, L-(3I)Tyr and D-(3I)Tyr.

11. The compound of claim 1 , wherein Z is L-Tic, D-Tic, L-Cha, D-Pro, 2-D-Nal or D-His.

12. The compound of claim 1 , selected from the group consisting of:

and salts thereof.

13. The compound of claim 1 , which is a compound of formula (I) selected from the group consisting of SEQ ID NO. 3-50, and SEQ ID NO. 58-108.

14. The compound of claim 1 , wherein the compound is a melanocortin-3 receptor (MC3R) agonist.

15. The compound of claim 1 , wherein the compound is a melanocortin-4 receptor (MC4R) antagonist.

16. The compound of claim 1 , wherein the compound is a melanocortin-3 receptor (MC3R) antagonist.

17. The compound of claim 1 , wherein the compound is not a melanocortin-4 receptor (MC4R) antagonist or agonist.

18. A composition comprising a compound of claim 1 , or a salt thereof, and a carrier.

19. A method for decreasing appetite in a mammal in need thereof, comprising administering an effective amount of a compound of claim 1 , or a pharmaceutically acceptable salt thereof, to the mammal, wherein the compound is a melanocortin-3 receptor (MC3R) antagonist.

20. A method of treating obesity in a mammal in need thereof, comprising administering an effective amount of a compound of claim 1 , or a pharmaceutically acceptable salt thereof, to the mammal, wherein the compound is a melanocortin-3 receptor (MC3R) antagonist.