FMO5 and cancer: Organoiridium(iii) complexes [(Cpxbiph)Ir(phpy)(Cl)] (38) and [(Cpxbiph)Ir(phpy)(py)]+ (39) (Fig. 12a) where Cpxbiph = biphenyltetramethylcyclopentadienyl, phpy = phenylpyridine and py = pyridine, can transfer the hydride from NADH via iridium-hydride intermediates to O2, a possible route for intracellular H2O2 generation.27 The activity of these complexes is analogous to that of NADPH oxidase which transfers hydride from NADPH to O2 in cells.50 These complexes were active against a wide range of cancer cell lines in the National Cancer Institute NCI-60 human cancer cell screen.