CB 1158 is a potent arginase inhibitor. CB-1158 has the potential for anti-tumor activity in renal cell cancer, breast cancer, non-small cell lung cancer, acute myeloid leukemia, and other tumor types where arginase-secreting MDSCs are known to play an immunosuppressive role. CB-1158 may also have the ability to combine with other immuno-oncology therapies that target T-cell activation, such as CTLVIP(LA)4 and PD-1 antibodies.