IDH1 (isocitrate dehydrogenase 1) mutations are found in approximately 10–15%, predominantly in the iCCA, particularly in the variants small duct-iCCA and cholangiolocarcinoma-iCCA.76,77 IDH1 mutations can be targeted by Ivosidenib, which is an oral IDH1 inhibitor that has been evaluated in the global, randomized, double-blind, placebo-controlled phase III clinical ClarIDHy trial enrolling patients with pretreated IDH1 mutant cholangiocarcinoma. The gene discussed is IDH1; the disease is cholangiocarcinoma.