An orally bioavailable inhibitor of mitochondrial complex I; inhibits the ubiquinone reduction activity of isolated murine mitochondrial complex I at 60 nM; reduces basal and spare respiratory capacities and increases glycolytic flux in primary CLL cells at 100 nM; induces apoptosis in CLL cells grown under low glucose conditions or when administered in combination with 2-deoxy-D-glucose; induces tumor regression in a glycolysis-deficient NB1 mouse xenograft model when administered at doses of 5 and 10 mg/kg