Human cells express three isocitrate dehydrogenases (IDHs): IDH1 is localised in the cytoplasm and IDH2 and IDH3 are localised in mitochondria.[10] The IDH1/2‐encoding genes are the most commonly mutated metabolic genes that are associated with cancer.[10, 11] Both IDH1 and IDH2 are homodimers that catalyse the NADP+‐dependent reversible oxidative decarboxylation of isocitrate to give 2‐oxoglutarate (2OG) and carbon dioxide (Figure 1B). The gene discussed is IDH2; the disease is cancer.