Docetaxel-Ifosfamide Combination in Patients with Advanced Breast Cancer Failing Prior Anthracycline- Based Regimens: Results of a Phase I-II Study

[Ifosphamide nephrotoxicity]

Ifosfamide is a cytotoxic drug usually used in malignant sarcomas. The nephrotoxicity of this agent has been described essentially among children, revealed by renal failure and proximal tubulopathy. We recently conducted a retrospective multicentre study, describing 34 adult patients admitted for ifosfamide nephrotoxicity. More than 80% of them presented with renal failure, diagnosed up to 48 months after ifosfamide administration. A Fanconi syndrome with hypophosphoremia, hypokaliemia, glucosuria and low-molecular weight proteinuria, was present in two third of all cases. Median estimated glomerular filtration rate was 31mL/min 1 month and 38mL/min 3 months after ifosfamide infusion, versus 67mL/min at baseline. Renal biopsy, performed in 14 of these patients, showed acute tubular necrosis with vacuolization of proximal tubular epithelial cells with marked nuclear modifications, whereas electron microscopy revealed major changes of mitochondrial structure inside those cells, suggesting a tenofovir-like mechanism of nephrotoxicity. After a median follow-up of 31 months, ten patients out of 34 reached stage 5 chronic kidney disease, requiring dialysis in five cases. Poor renal prognosis was associated with concomitant cisplatin use (P=0.02) and with older age at presentation (P=0.04). In conclusion, ifosfamide nephrotoxicity is often severe and irreversible, leading to proximal tubulopathy and sometimes-severe chronic kidney failure, that can be immediate or delayed, sometimes diagnosed months after chemotherapy completion.

Hydroxylation and N-dechloroethylation of Ifosfamide and deuterated Ifosfamide by the human cytochrome p450s and their commonly occurring polymorphisms

The hydroxylation and N-dechloroethylation of deuterated ifosfamide (d4IFO) and ifosfamide (IFO) by several human P450s have been determined and compared. d4IFO was synthesized with deuterium at the alpha and alpha' carbons to decrease the rate of N-dechloroethylation and thereby enhance hydroxylation of the drug at the 4' position. The purpose was to decrease the toxic and increase the efficacious metabolites of IFO. For all of the P450s tested, hydroxylation of d4IFO was improved and dechloroethylation was reduced as compared with nondeuterated IFO. Although the differences were not statistically significant, the trend favoring the 4'-hydroxylation pathway was noteworthy. CYP3A5 and CYP2C19 were the most efficient enzymes for catalyzing IFO hydroxylation. The importance of these enzymes in IFO metabolism has not been reported previously and warrants further investigation. The catalytic ability of the common polymorphisms of CYP2B6 and CYP2C9 for both reactions were tested with IFO and d4IFO. It was determined that the commonly expressed polymorphisms CYP2B6*4 and CYP2B6*6 had reduced catalytic ability for IFO compared with CYP2B6*1, whereas CYP2B6*7 and CYP2B6*9 had enhanced catalytic ability. As with the wild-type enzymes, d4IFO was more readily hydroxylated by the polymorphic variants than IFO, and d4IFO was not dechloroethylated by any of the polymorphic forms. We also assessed the use of specific inhibitors of P450 to favor hydroxylation in human liver microsomes. We were unable to separate the pathways with these experiments, suggesting that multiple P450s are responsible for catalyzing both metabolic pathways for IFO, which is not observed with the closely related drug cyclophosphamide.

Ifosfamide metabolite chloroacetaldehyde inhibits cell proliferation and glucose metabolism without decreasing cellular ATP content in human breast cancer cells MCF-7

Chloroacetaldehyde (CAA), a product of hepatic metabolism of the widely used anticancer drug ifosfamide (IFO), has been reported to decrease cancer cell proliferation. The basis of this effect is not completely known but has been attributed to a drop of cellular ATP content. Given the importance of glucose metabolism and of the 'Warburg effect' in cancer cells, we examined in the present study the ability of CAA to inhibit cancer cell proliferation by altering the glycolytic pathway. Cell proliferation, ATP content, glucose transport and metabolism as well as the activities of the main enzymes of glycolysis were determined in human breast cancer cells MCF-7 in the presence of various CAA concentrations (5-50 microm). Our results show that low CAA concentrations inhibited cell proliferation in a concentration-dependent manner. This inhibition was explained by a decrease in glucose utilization. Cellular ATP content was not reduced but even increased with 25 microm CAA. The inhibition of glucose metabolism was mainly explained by the decrease in glucose transport and hexokinase activity. The activity of glyceraldehyde-3-phosphate dehydrogenase, but not that of phosphofructokinase, was also inhibited. Glycolysis inhibition by CAA was effective in decreasing the proliferation of MCF-7 cells. Interestingly, this decrease was not due to ATP depletion; rather, it was linked to a drop of biosynthetic precursors from glycolytic intermediates. This CAA-induced inhibition of cell proliferation suggests that it might play a role in the antitumor activity of IFO.