1,2,4-oxadiazole derivatives as immunomodulators

1. A method of modulating an immune response mediated by a PD-1 signaling pathway in a subject, comprising administering to the subject a compound of formula (I) or a pharmaceutically acceptable salt or a pharmaceutically acceptable composition thereof:

wherein,

Q is S or O;

R 1 represents a side chain of an amino acid residue Ser or Thr, optionally substituted with alkyl or acyl;

R 2 is hydrogen or —CO-Aaa;

Aaa is an amino acid residue selected from Thr and Ser; wherein a C-terminus thereof is a free terminus, is amidated, or is esterified;

R 3 represents a side chain of an amino acid residue selected from Asn, Asp, Gln, and Glu;

----- is an optional bond;

R 4 and R 5 independently are hydrogen or absent; and

R 6 is hydrogen, alkyl, or acyl.

2. The method of claim 1 , wherein Q is O.

3. The method of claim 1 , wherein R 6 is H.

4. The method of claim 1 , wherein R 6 is —C(O)CH 3 , —C(O)CH 2 CH 3 , —C(O)(CH 2 ) 2 CH 3 , —C(O)(CH 2 ) 3 CH 3 , —C(O)(CH 2 ) 4 CH 3 or —C(O)(CH 2 ) 5 CH 3 .

5. The method of claim 1 , wherein R 2 is —CO-Aaa.

6. The method according to claim 1 , wherein the compound of formula (I) is a compound of formula (IA):

or a pharmaceutically acceptable salt thereof; wherein,

R 1 represents a side chain of an amino acid residue Ser or Thr, optionally substituted with alkyl or acyl;

R 3 represents a side chain of an amino acid residue selected from Asn, Asp, Gln, and Glu; and

Aaa is an amino acid residue selected from Thr and Ser; wherein the C-terminus thereof is a free terminus, is amidated, or is esterified.

7. The method according to claim 1 , wherein Aaa is an amino acid residue selected from Thr and Ser; wherein the C-terminus is a free terminus.

8. The method according to claim 1 , wherein the compound of formula (I) is a compound of formula (IB):

or a pharmaceutically acceptable salt thereof; wherein,

R 1 represents a side chain of an amino acid residue Ser or Thr, optionally substituted with alkyl or acyl; and

R 3 represents a side chain of an amino acid residue selected from Asn, Asp, Gln, and Glu.

9. The method according to claim 1 , wherein R 1 represents a side chain of an amino acid residue Ser or Thr.

10. The method according to claim 1 , wherein R 1 is substituted with C 1-5 alkyl.

11. The method according to claim 1 , wherein R 3 represents a side chain of an amino acid residue Asn or Glu.

12. The method according to claim 1 , wherein:

R 1 represents a side chain of an amino acid residue Ser or Thr;

R 2 is CO-Aaa;

Aaa is an amino acid residue selected from Thr and Ser; wherein the C-terminus is a free terminus; and

R 3 represents a side chain of an amino acid residue Asn or Glu.

13. The method according to claim 1 , wherein R 1 represents a side chain of an amino acid residue Ser.

14. The method according to claim 1 , wherein R 1 represents a side chain of an amino acid residue Thr.

15. The method according to claim 1 , wherein Aaa is Ser.

16. The method according to claim 1 , wherein Aaa is Thr.

17. The method according to claim 1 , wherein R 3 represents a side chain of an amino acid residue Asn.

18. The method according to claim 1 , wherein R 3 represents a side chain of an amino acid residue Asp.

19. The method according to claim 1 , wherein R 3 represents a side chain of an amino acid residue Gln.

20. The method according to claim 1 , wherein R 3 represents a side chain of an amino acid residue Glu.

21. The method of claim 1 , wherein R 2 is H.

22. The method according to claim 1 , wherein the compound of formula (I) has the following structure:

or a pharmaceutically acceptable salt thereof.

23. The method according to claim 1 , wherein the compound of formula (I) has the following structure:

or a pharmaceutically acceptable salt thereof.

24. The method according to claim 1 , wherein the compound of formula (I) has the following structure:

or a pharmaceutically acceptable salt thereof.

25. The compound according to claim 1 , wherein the compound of formula (I) has the following structure:

or a pharmaceutically acceptable salt thereof.

26. The method according to claim 1 , wherein the compound of formula (I) has the following structure:

or a pharmaceutically acceptable salt thereof.

27. The method according to claim 1 , wherein the compound of formula (I) has the following structure:

or a pharmaceutically acceptable salt thereof.

28. The method according to claim 1 , wherein the compound of formula (I) has the following structure:

or a pharmaceutically acceptable salt thereof.

29. The method according to claim 1 , wherein the compound of formula (I) has the following structure:

or a pharmaceutically acceptable salt thereof.

30. The method according to claim 1 , wherein the compound of formula (I) has the following structure:

or a pharmaceutically acceptable salt thereof.

31. The method according to claim 1 , wherein the compound of formula (I) has the following structure:

or a pharmaceutically acceptable salt thereof.

32. The method according to claim 1 , wherein the compound of formula (I) has the following structure:

or a pharmaceutically acceptable salt thereof.

33. The method according to claim 1 , wherein the compound of formula (I) has the following structure:

or a pharmaceutically acceptable salt thereof.

34. The method according to claim 1 , wherein the compound of formula (I) has the following structure:

or a pharmaceutically acceptable salt thereof.

35. The method according to claim 1 , wherein the compound of formula (I) has the following structure:

or a pharmaceutically acceptable salt thereof.

36. The method according to claim 1 , wherein the compound of formula (I) has the following structure:

or a pharmaceutically acceptable salt thereof.

37. The method according to claim 1 , wherein the compound of formula (I) has the following structure:

or a pharmaceutically acceptable salt thereof.

38. The method according to claim 1 , wherein the compound of formula (I) has the following structure:

or a pharmaceutically acceptable salt thereof.

39. The method according to claim 1 , wherein the compound of formula (I) has the following structure:

or a pharmaceutically acceptable salt thereof.

40. The method according to claim 1 , wherein the compound of formula (I) has the following structure:

or a pharmaceutically acceptable salt thereof.

41. The method according to claim 1 , wherein the compound of formula (I) has the following structure:

or a pharmaceutically acceptable salt thereof.

42. The method according to claim 1 , wherein the compound of formula (I) has the following structure:

or a pharmaceutically acceptable salt thereof.

43. The method according to claim 1 , wherein the compound of formula (I) has the following structure:

or a pharmaceutically acceptable salt thereof.

44. The method according to claim 1 , wherein the compound of formula (I) has the following structure:

or a pharmaceutically acceptable salt thereof.

45. The method according to claim 1 , wherein the compound of formula (I) has the following structure:

or a pharmaceutically acceptable salt thereof.

46. The method according to claim 1 , wherein the compound of formula (I) has the following structure:

or a pharmaceutically acceptable salt thereof.

47. The method of claim 1 , wherein the subject is suffering from a cancer.

48. The method of claim 47 , wherein the cancer is selected from breast cancer, colon cancer, lung cancer, melanoma, prostate cancer, and renal cancer.

49. The method of claim 47 , wherein the cancer is selected from bone cancer, cancer of the head or neck, pancreatic cancer, skin cancer, cutaneous or intraocular malignant melanoma, carcinoma of the endometrium, carcinoma of the cervix, carcinoma of the vagina, carcinoma of the vulva, Hodgkin's Disease, non-Hodgkin's lymphoma, cancer of the esophagus, cancer of the small intestine, cancer of the endocrine system, cancer of the thyroid gland, cancer of the parathyroid gland, cancer of the adrenal gland, sarcoma of soft tissue, cancer of the urethra, cancer of the penis, chronic or acute leukemias including acute myeloid leukemia, chronic myeloid leukemia, acute lymphoblastic leukemia, chronic lymphocytic leukemia, solid tumors of childhood, lymphocytic lymphoma, cancer of the bladder, cancer of the kidney or ureter, carcinoma of the renal pelvis, neoplasm of the central nervous system (CNS), primary CNS lymphoma, tumor angiogenesis, spinal axis tumor, brain stem glioma, pituitary adenoma, Kaposi's sarcoma, epidermoid cancer, squamous cell cancer, T-cell lymphoma, environmentally induced cancers, and combinations of said cancers.

50. The method of claim 47 , wherein the method inhibits metastasis of the cancer.

51. The method of claim 1 , where the subject is suffering from an infectious disease.

52. The method of 51 , wherein the infectious disease is a bacterial infectious disease, a viral infectious disease, or a fungal infectious disease.

53. The method of claim 52 , wherein the infectious disease is selected from HIV, Influenza, Herpes, Giardia , Malaria, Leishmania , the pathogenic infection by the virus Hepatitis A, Hepatitis B, Hepatitis C, herpes virus VZV, HSV-I, HAV-6, HSV-II, and CMV, Epstein Barr virus, adenovirus, influenza virus, flaviviruses, echovirus, rhinovirus, coxsackie virus, cornovirus, respiratory syncytial virus, mumps virus, rotavirus, measles virus, rubella virus, parvovirus, vaccinia virus, HTLV virus, dengue virus, papillomavirus, molluscum virus, poliovirus, rabies virus, JC virus and arboviral encephalitis virus, pathogenic infection by the bacteria chlamydia, rickettsial bacteria, mycobacteria, staphylococci, streptococci, pneumonococci, meningococci and conococci, klebsiella, proteus, serratia, pseudomonas, E. coli , legionella, diphtheria, salmonella, bacilli, cholera, tetanus, botulism, anthrax, plague, leptospirosis, and Lyme's disease bacteria, pathogenic infection by the fungi Candida albicans, Candida krusei, Candida glabrata, Candida tropicalis, Cryptococcus neoformans, Aspergillus, umigatus, niger , Genus Mucorales, mucor, absidia, rhizophus, Sporothrix schenkii, Blastomyces dermatitidis, Paracoccidioides brasiliensis, Coccidioides immitis and Histoplasma capsulatum , and pathogenic infection by the parasites Entamoeba histolytica, Balantidium coli, Naegleria fowleri, Acanthamoeba sp., Giardia lambia, Cryptosporidium sp., Pneumocystis carinii, Plasmodium vivax, Babesia microti, Trypanosoma brucei, Trypanosoma cruzi, Leishmania donovani, Toxoplasma gondi , or Nippostrongylus brasiliensis.