Activation of the anticancer drugs cyclophosphamide and ifosfamide by cytochrome P450 BM3 mutants

Galvin Vredenburg, Shalenie den Braver-Sewradj, Barbara M A van Vugt-Lussenburg, Nico P E Vermeulen, Jan N M Commandeur, J Chris Vos

Research output: Contribution to JournalArticleAcademicpeer-review


Cyclophosphamide (CPA) and ifosfamide (IFA) are widely used anticancer agents that require metabolic activation by cytochrome P450 (CYP) enzymes. While 4-hydroxylation yields DNA-alkylating and cytotoxic metabolites, N-dechloroethylation results in the generation of neuro- and nephrotoxic byproducts. Gene-directed enzyme prodrug therapies (GDEPT) have been suggested to facilitate local CPA and IFA bioactivation by expressing CYP enzymes within the tumor cells, thereby increasing efficacy. We screened bacterial CYP BM3 mutants, previously engineered to metabolize drug-like compounds, for their ability to catalyze 4-hydroxylation of CPA and IFA. Two CYP BM3 mutants showed very rapid initial bioactivation of CPA and IFA, followed by a slower phase of product formation. N-dechloroethylation by these mutants was very low (IFA) to undetectable (CPA). Using purified CYP BM3 as an extracellular bioactivation tool, cytotoxicity of CPA and IFA metabolism was confirmed in U2OS cells. This novel application of CYP BM3 possibly provides a clean and catalytically efficient alternative to liver microsomes or S9 for the study of CYP-mediated drug toxicity. To our knowledge, the observed rate of CPA and IFA 4-hydroxylation by these CYP BM3 mutants is the fastest reported to date, and might be of potential interest for CPA and IFA GDEPT.

Original languageEnglish
Pages (from-to)182-92
Number of pages11
JournalToxicology Letters
Issue number1
Publication statusPublished - 5 Jan 2015


  • Activation, Metabolic
  • Antineoplastic Agents, Alkylating
  • Bone Neoplasms
  • Cell Line, Tumor
  • Cell Survival
  • Cyclophosphamide
  • Cytochrome P-450 CYP2B6
  • Dose-Response Relationship, Drug
  • Genotype
  • Humans
  • Hydroxylation
  • Ifosfamide
  • Kinetics
  • Microsomes, Liver
  • Mutation
  • Osteosarcoma
  • Phenotype
  • Journal Article


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