Abstract
Ifosfamide is a well known prodrug for cancer treatment with cytochrome P450 metabolism. It is associated with both antitumor activity and toxicities. Isophosphoramide mustard is the bisalkylating active metabolite, and acrolein is a urotoxic side product. Because acrolein toxicity is limited by coadministration of sodium mercaptoethanesulfonate, the incidence of urotoxicity has been lowered. Current evidence suggests that chloroacetaldehyde, a side-chain oxidation metabolite, is responsible for neurotoxicity and nephrotoxicity. The aim of our research is to prevent chloroacetaldehyde formation using new enantioselectively synthesized ifosfamide analogs, i.e., C7,C9-dimethyl-ifosfamide. We hypothesize that reduced toxicogenic catabolism may induce less toxicity without changing anticancer activity. Metabolite determinations of the dimethyl-ifosfamide analogs were performed using liquid chromatography and tandem mass spectrometry after in vitro biotransformation by drug-induced rat liver microsomes and human microsomes expressing the main CYP3A4 and minor CYP2B6 enzymes. Both human and rat microsomes incubations produced the same N-deschloroalkylated and 4-hydroxylated metabolites. A coculture assay of 9L rat glioblastoma cells and rat microsomes was performed to evaluate their cytotoxicity. Finally, a mechanistic study using 31P NMR kinetics allowed estimating the alkylating activity of the modified mustards. The results showed that C7,C9-dimethyl-ifosfamide exhibited increased activities, although they were still metabolized through the same N-deschloroalkylation pathway. Analogs were 4 to 6 times more cytotoxic than ifosfamide on 9L cells, and the generated dimethylated mustards were 28 times faster alkylating agents than ifosfamide mustards. Among these new ifosfamide analogs, the 7S,9R-enantiomer will be assessed for further in vivo investigations for its anticancer activity and its toxicological profile.
Footnotes
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This work was supported by Académie Nationale de Médecine and Baxter Oncology, France. This work was presented previously in abstract form: Storme T, Derousseut A, Mercier L, Prost E, Re M, Munier F, Marleus T, Bourget P, Vassal G, Royer J, et al. (2007) New ifosfamide analogs aiming less neurotoxicity and less nephrotoxicity. AACR Meeting Abstracts abst. 5591.
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T.S. and A.P. contributed equally to this work.
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Article, publication date, and citation information can be found at http://jpet.aspetjournals.org.
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doi:10.1124/jpet.108.144170.
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ABBREVIATIONS: IFO, ifosfamide; 4-OH-IFO, 4-hydroxy-ifosfamide; IPM, isophosphoramide mustard; P450, cytochrome P450; N2-DCE-IFO, N2-deschloroethyl-ifosfamide; N3-DCE-IFO, N3-deschloroethyl-ifosfamide; N2,N3-diDCE-IFO, N2-,N3-dideschloroethyl-ifosfamide; CAA, chloroacetaldehyde; C7,C9-diMe-IFO, dimethyl-ifosfamide analogs; TS121, 7S,9R-dimethyl-ifosfamide; TS125, 7S,9S-dimethyl-ifosfamide; ESI, electrospray ionization; HPLC, high-performance liquid chromatography; MTT, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide; DMEM, Dulbecco's modified Eagle's medium; FBS, fetal bovine serum; MS/MS, tandem mass spectrometry; diMe, dimethylated; CPM, cyclophosphamide; N2-DCP-Me-IFO, N2-deschloropropyldimethyl-ifosfamide; N3-DCP-Me-IFO, N3-deschloropropyldimethyl-ifosfamide; 4-OH-diMe-IFO, 4-hydroxy-dimethyl-ifosfamide; Alk, alkylation.
- Received July 31, 2008.
- Accepted November 17, 2008.
- The American Society for Pharmacology and Experimental Therapeutics
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