,4 Early reports suggested that cancer-associated IDH1 mutations also caused a “simple” loss of the ability to catalyze conversion of isocitrate to 2-oxoglutarate (2-OG),5 also known as α-ketoglutarate, and that wild-type (WT) IDH1 activity was dominantly inhibited by formination of a heterodimer with mutant IDH1 (mutIDH1).6 The gene discussed is IDH1; the disease is cancer.