CYP1A1 and cancer: It was thereafter irrefutably demonstrated that CYP1A1 and CYP2W1 are able to catalyse production of 5F 203‐derived hydroxylamine, and guanine DNA adducts presumably via nitrenium species production, underpinning the selective antitumour cytotoxic activity of 5F 203.6 5F 203 treatment consequently resulted in lethal DNA adducts, double‐strand breaks and selective cancer cell death.8