The L isomer (1-L-MT) is the more potent inhibitor of IDO1, whereas the D isomer (1-D-MT, Indoximod) exhibited significantly higher anti-tumor activity by reversing T-cell function and synergizing with chemotherapy agents (16) but is a more selective IDO2 inhibitor (17) which metabolizes tryptophan much less efficiently than IDO1 (18, 19). The gene discussed is IDO1; the disease is neoplasm.