Preclinical Drug Metabolism, Pharmacokinetic, and Pharmacodynamic Profiles of Ivosidenib, an Inhibitor of Mutant Isocitrate Dehydrogenase 1 for Treatment of Isocitrate Dehydrogenase 1-Mutant Malignancies

Point mutations in isocitrate dehydrogenase 1 () result in conversion of -ketoglutarate to the oncometabolite, d-2-hydroxyglutarate (2-HG). Ivosidenib is a once daily (QD), orally available, potent, mutant isocitrate dehydrogenase 1 (mIDH1) inhibitor approved for the treatment of patients with relapsed or refractory acute myeloid leukemia (AML) and intensive chemotherapy-ineligible newly diagnosed AML, with a susceptible mutation. We characterized the protein binding, metabolism, metabolites, cell permeability, and drug-drug interaction potential of ivosidenib in humans, monkeys, dogs, rats, and/or mice in in vitro experiments. In vivo pharmacokinetic (PK) profiling and assessment of drug distribution and excretion was undertaken in rats, dogs, and monkeys administered single-dose ivosidenib. The PK/pharmacodynamic (PD) relationship between ivosidenib and 2-HG was analyzed in an m xenograft mouse model. Ivosidenib was well absorbed, showed low clearance, and moderate to long terminal half-life (5.3-18.5 hours) in rats, dogs, and monkeys. Brain to plasma exposure ratio was low (2.3%), plasma protein binding was high, and oxidative metabolism was the major elimination pathway. Ivosidenib had high cell permeability and was identified as a substrate for P-glycoprotein. There was moderate induction of cytochrome P450 (P450) enzymes CYP3A4 and CYP2B6 but minimal P450 inhibition or autoinduction. Tumor 2-HG reduction appeared to be dose- and drug-exposure-dependent. Ivosidenib showed a favorable PK profile in several animal species, along with a clear PK/PD relationship demonstrating 2-HG inhibition that translated well to patients with AML. SIGNIFICANCE STATEMENT: Ivosidenib is a mutant IDH1 (mIDH1) inhibitor approved for the treatment of certain patients with m acute myeloid leukemia. In Sprague-Dawley rats, beagle dogs, and cynomolgus monkeys, ivosidenib demonstrated a favorable pharmacokinetic profile, and in female BALB/c mice showed clear dose- and exposure-dependent inhibition of the oncometabolite, d-2-hydroxyglutarate, which is present at abnormal levels in m tumors. These findings led to the further development of ivosidenib and are consistent with data from patients with m cancers and healthy participants.