Navoximod (formerly NLG 919, GDC 0919), a small molecule, orally bioavailable, immune checkpoint inhibitor, is being developed by NewLink Genetics for the treatment of solid tumours. Navoximod is a potent IDO (indoleamine-(2,3)-dioxygenase) pathway inhibitor with Ki/EC50 of 7 nM/75 nM. Upon administration, navoximod targets and binds to IDO1, a cytosolic enzyme responsible for the oxidation of the essential amino acid tryptophan into kynurenine. By inhibiting IDO1 and decreasing kynurenine in tumor cells, this agent increases tryptophan levels, restores the proliferation and activation of various immune cells, including dendritic cells (DCs), natural killer (NK) cells, and T-lymphocytes, and causes a reduction in tumor-associated regulatory T-cells (Tregs). Activation of the immune system, which is suppressed in many cancers, may induce a cytotoxic T-lymphocyte (CTL) response against the IDO1-expressing tumor cells. IDO1 is overexpressed by a variety of tumor cell types and plays an important role in immunosuppression. Tryptophan depletion is associated with immunosuppression caused by T-cell suppression. Navoximod is under investigation in clinical trial NCT02048709 (Indoleamine 2,3-Dioxygenase (IDO) inhibitor in advanced solid tumors).

CG-200745 is a novel inhibitor of histone deacetylases (HDACs), initially developed by CrystalGenomics, Inc for treatment of various hematological and solid cancers. Combinations of CG-200745 with SN38 (the active form of irinotecan), or oxaliplatin were more effective than the agents alone when used to inhibit the growth of HCT116 cells. The protein expressions of acetyl-H3, p21, caspase-3, -8, and -9, PARP, and XIAP were affected in a time- and dose-dependent manner in HCT116 cells treated with the CG-200745 alone or combined CG-200745 and SN-38. In HCT116 xenografts, the HDACI CG-200745 in combination with irinotecan dramatically inhibited tumor growth without showing additive toxicity.

Cenerimod is an orally available sphingosine-1-phosphate receptor 1 (S1P1) modulator that is being developed by Idorsia Pharmaceuticals for the treatment of systemic lupus erythematosus. Sphingosine-1-phosphate (S1P), a lipid mediator, regulates lymphocyte migration between lymphoid tissue and blood. Cenerimod is a potent, selective, safe and orally administrable S1P1 receptor modulator, which reportedly reduced blood lymphocytes and attenuated murine experimental autoimmune encephalomyelitis (EAE) in a murine model. Cenerimod has potential as novel therapy with an improved safety profile for autoimmune diseases with a high unmet medical need.

LX 2931 (LX 3305) is an inhibitor of sphingosine 1-phosphate (S1P) lyase. S1P lyase is an enzyme identified as a promising new target on a pathway associated with regulation of the immune system. Lexicon Pharmaceuticals, Inc. was developing LX 2931 for the treatment of rheumatoid arthritis. LX 2931 has disappeared from the pipeline of Lexicon Pharmaceuticals, Inc. In preclinical studies LX 2931 was effective against experimental cerebral malaria, lung inflammation in a F508del CFTR murine cystic fibrosis model and osteoporosis.

KYORIN Pharmaceutical has developed a new sphingosine 1-phosphate (S1P) receptor type 1 agonist, 2-amino-2-propanediol hydrochloride (KRP-203), for immunomodulation in autoimmune diseases and organ transplantation. This drug was in phase II clinical trial for the treatment Ulcerative Colitis, but this study was terminated. In addition, it has been investigated for the treatment of Cutaneous Lupus Erythematosus and Crohn's Disease, these phases II clinical trial studies were successfully completed.

NSI-189 is a novel oral drug which was developed by Neuralstem for the treatment of cognitive disorders. Now the drug is being tested in phase II of clinical trials in patients suffering from major depressive disorder. The mechanism of NSI-189 action is explained by its ability to stimulate the generation of new neurons in the hippocampus, however the exact target molecule is still unknown.