IDH2 and central nervous system cancer: These inhibitors have been evaluated in several studies with heterogeneous populations of patients with IDH-mutant grades 2–4 gliomas, both in patients with enhancing and non-enhancing tumors (Table 5).4–6,143,144 All the initial studies of IDH inhibitors were conducted in patients with recurrent/progressive gliomas where the histology was usually based on prior resections rather than on tumor samples obtained immediately before study entry.5,6,143–146