Bioreductive agents are ideally suited for enzyme-directed tumor targeting because they must be activated in cells by reductive enzymes.1,2 NQO1 has been extensively used as a target for this strategy because it is found in all tissues,24,26 and is preferentially expressed in tumor cells.24,26,27 In addition, NQO1 levels are generally low in hematopoetic cells.26 Thus, agents, like RH1, that are selectively activated by NQO1,14 have been developed to target tumors with high NQO1 levels and to avoid bone marrow toxicity. The gene discussed is NQO1; the disease is neoplasm.