Olutasidenib (REZLIDHIA TM ), an isocitrate dehydrogenase-1 (IDH1) inhibitor, is being developed by Rigel Pharmaceuticals for the treatment of relapsed or refractory (R/R) acute myeloid leukaemia (AML). Olutasidenib was recently approved in the USA for the treatment of adults with R/R AML with a susceptible IDH1 mutation as detected by a US Food and Drug Administration-approved test. This article summarizes the milestones in the development of olutasidenib leading to this first approval for R/R AML.