Trimidox (hydrochloride) is a specific ribonucleotide reductase inhibitor [1][2][3]. Ribonucleotide reductase is the rate-limiting enzyme for de novo DNA synthesis. This enzyme is linked with proliferation and malignant transformation, and is a common target for cancer chemotherapy [1][2]. Trimidox (hydrochloride) is a specific ribonucleotide reductase inhibitor. Trimidox inhibited the activity of ribonucleotide reductase in extracts of L1210 cells with IC50 value of 5 μM. Trimidox was cytotoxic to L1210 cells with IC50 value of 7.5 μM [3]. In human promyelocytic leukemia HL-60 cells, Trimidox inhibited cell growth with IC50 value of 35 μmol/L. Trimidox (50 μmol/L) reduced deoxyguanosine triphosphate (dGTP) and deoxycytidine triphosphate
