IDH2 and central nervous system cancer: 2-HG is a metabolite which is normally present at very low levels in cells [17], 2-HG levels have been found to be elevated in IDH-mutant glioma samples, and Gross et al. reported that IDH1 R132 mutations also lead to production and accumulation of 2-HG in AML blasts, greater than 50-fold higher than their nonmutant counterparts.