In vitro studies of the hyperthermic enhancement of activated ifosfamide (4-hydroperoxy-ifosfamide) and glucose isophosphoramide mustard

Purpose: To study the effect of hyperthermia on the cytotoxicity of glucose isophosphoramide mustard (D-19575), a derivative of ifosfamide, which does not require activation and preclinically demonstrates less nephrotoxicity and myelosuppression than ifosfamide.Methods: In vitro studies (using a crystal violet cell survival assay) of the interaction of hyperthermia with D-19575, as well as the activated form of ifosfamide (4-hydroperoxy-ifosfamide, D-18851), were performed using L929 and OVCAR-3 cell lines held at various temperatures (i.e. 37 °C (control), 40.5 °C, 41.8 °C, 42.5 °C, and 43 °C) for 65 min.Results: The following thermal enhancement ratios (TER) were demonstrated: D-19575 in L929 1.2, 2.0 and 2.3 at 40.5, 41.8 and 42.5 °C, respectively; for D-18851 in L929 1.7 at 41.8 °C; for D-19575 in OVCAR-3 2.1, 3.2 and 3.3 at 40.5, 41.8 and 42.5 °C, respectively; for D-18851 in OVCAR-3 4.6 at 41.8 °C. Conclusion: The significant observed increase in cytotoxicity of D-19575 caused by hyperthermia taken together with its known preclinical toxicity profile, encourage its further preclinical and ultimately clinical testing, including its use with whole body and regional hyperthermia.