Ifosfamide (IFF) is a nitrogen mustard with significant activity against a number of tumors. Since it is a chiral molecule, it has been suggested that enantioselective metabolism could result in different efficacy and toxicity profiles for (R)- and (S)-ifosfamide. Both experimental animal and clinical data suggest that N-dechloroethyl metabolites of (S)-IFF are more significantly associated with neurological toxicity, which may limit therapeutic use of IFF. We have used purified ifosfamide enantiomers to examine the pharmacokinetics; spectrum of toxicity including lethality, weight loss, and myelosuppression; and antitumor effects of the mixture compared to each of the purified enantiomers. In the MatB mammary carcinoma grown in female Fischer rats we demonstrated that the anti-tumor efficacy appears to be the same for (R)-IFF and (S)-IFF, while the (R)-IFF has greater myelotoxicity. Pharmacokinetic analysis of plasma concentration-time confirms that the (R)-IFF is metabolized to a greater extent than (S)-IFF via the activation pathway. These data suggest that purified (R)-IFF may be an effective way to deliver active cytotoxic drug while limiting the generation of neurotoxic metabolites.

1

This work was supported by grants from the Cancer Research Society and Martinex Research, Inc.

This content is only available via PDF.