GLS1 inhibitor is an inhibitor of glutaminase 1 (GLS1; IC50 = 0.021 μM). It inhibits the growth of NCI H1703 non-small cell lung cancer (NSCLC) cells in vitro (GI50 = 0.011 μM). GLS1 inhibitor (100 mg/kg) reduces tumor growth, increases tumor levels of glutamine, and decreases tumor levels of glutamate and aspartate in an NCI H1703 mouse xenograft model.