DHODH inhibitors have been previously shown to be highly effective against various cancers (Hail et al., 2010; O’Donnell et al., 2012; Sykes et al., 2016; Ladds et al., 2018b), and one of the most potent inhibitors, brequinar, even made it to clinical trials in the early 1990s for the treatment of a variety of solid tumours, though it was judged to be too toxic to patients in light of its modest clinical outcomes (Dexter et al., 1985; Arteaga et al., 1989; Natale et al., 1992; Urba et al., 1992; Cody et al., 1993; Maroun et al., 1993; Moore et al., 1993). This evidence concerns the gene DHODH and cancer.