RRM1 and cancer: It is also a potential predictor for identifying good responders to chemotherapy for CRC.23 In contrast to RRM2, both RRM1 and RRM2B are associated with a better prognosis for cancer patients.22,24–27 Therefore, it is suggested that, besides the antiproliferative activity of RR inhibition, the specific inhibition of RRM2 expression might provide additional anticancer benefits.28 Given the fact that current clinically used RR inhibitors, such as gemcitabine and hydroxyurea, lack specific activity for RRM2, the development of novel RRM2 inhibitors is of immediate importance.