Ifosfamide (IFA) is a potent alkylating antitumoral agent, but its use is limited by neurological side effects. IFA is a racemic mixture of two enantiomeric forms, R-IFA and S-IFA with a stereoselective metabolism by CYP3A4 and CYP2B6, leading either to bioactive or to toxic pathways. In three consecutive cases of pediatric patients who exhibited IFA-induced encephalopathy (IIE), genotyping of clinically relevant single-nucleotide polymorphisms associated with decreased CYP3A4 and CYP2B6 activities was performed. Genetic investigations revealed the presence of CYP2B6 rs4803419 (C>T) in one patient while the two others carried the CYP2B6*6 allelic variant. All patients carried CYP3A4 wild-type genotype (CYP3A4*1/*1). Because CYP2B6-deficient alleles may be responsible for an increased conversion of S-IFA into neurotoxic metabolites, screening for CYP2B6 polymorphisms may help to avoid IIE and improve clinical outcomes.
Keywords: CYP2B6; encephalopathy; ifosfamide metabolism; methylene blue; pharmacogenetics.
© 2018 Société Française de Pharmacologie et de Thérapeutique.