CYP2C8 and cancer: 2020). Given that cancer patients often take multiple drugs, whether the combination of tucatinib and other drugs would cause drug–drug interactions (DDIs) must be explored. CYP2C8 was proved to be the major metabolic enzyme in vitro, in addition to CYP3A to a lesser extent (Lee 2020). It was reported that gemfibrozil (a strong CYP2C8 inhibitor) increased the exposure of tucatinib when they were given with concomitant administration (Lee 2020).