IDH1 (isocitrate dehydrogenase [NADP] cytoplasmic) catalyzes the conversion of isocitrate to alpha-ketoglutarate (alpha-KG). Mutations in IDH1 convert alpha-KG to 2-HG, which is an oncogenic metabolite. Simple variants in IDH1 are seen in about 11% of all tumors, including about 35% of all central nervous system tumors. Mutations in IDH1 are diagnostic for low grade glioma and secondary glioblastoma, and correlate with a better prognosis in glioblastoma. IDH1 inhibitors are also being developed.