CB-1158 is an inhibitor of arginase I and II (IC₅₀s = 0.086 and 0.296 µM for the human enzymes, respectively).¹It is selective for arginase I and II over neuronal nitric oxide synthase (nNOS), endothelial NOS (eNOS), and inducible NOS (iNOS; IC₅₀s = >50 µM for all). CB-1158 reverses inhibition of T cell proliferation induced by granulocytesin vitro(IC₅₀= 0.204 µM). It reduces tumor growth in a CT26 murine colon cancer model when administered at a dose of 100 mg/kg twice per day.

1.Steggerda, S.M., Bennett, M.K., Chen, J., et al.Inhibition of arginase by CB-1158 blocks myeloid cell-mediated immune suppression in the tumor microenvironmentJ. Immunother. Cancer5(1)101(2017)