Intrathecal mafosfamide: a preclinical pharmacology and phase I trial.

PURPOSE: Preclinical studies of mafosfamide, a preactivated cyclophosphamide analog, were performed to define a tolerable and potentially active target concentration for intrathecal (IT) administration. A phase I and pharmacokinetic study of IT mafosfamide was performed to determine a dose for subsequent phase II trials. PATIENTS AND METHODS: In vitro cytotoxicity studies were performed in MCF-7, Molt-4, and rhabdomyosarcoma cell lines. Feasibility and pharmacokinetic studies were performed in nonhuman primates. These preclinical studies were followed by a phase I trial in patients with neoplastic meningitis. There were five dose levels ranging from 1 mg to 6.5 mg. Serial CSF samples were obtained for pharmacokinetic studies in a subset of patients with Ommaya reservoirs. RESULTS: The cytotoxic target exposure for mafosfamide was 10 micromol/L. Preclinical studies demonstrated that this concentration could be easily achieved in ventricular CSF after intraventricular dosing. In the phase I clinical trial, headache was the dose-limiting toxicity. Headache was ameliorated at 5 mg by prolonging the infusion rate to 20 minutes, but dose-limiting headache occurred at 6.5 mg dose with prolonged infusion. Ventricular CSF mafosfamide concentrations at 5 mg exceeded target cytotoxic concentrations after an intraventricular dose, but lumbar CSF concentrations 2 hours after the dose were less than 10 micromol/L. Therefore, a strategy to alternate dosing between the intralumbar and intraventricular routes was tested. Seven of 30 registrants who were assessable for response had a partial response, and six had stable disease. CONCLUSION: The recommended phase II dose for IT mafosfamide, administered without concomitant analgesia, is 5 mg over 20 minutes.

Cerebrospinal fluid penetration of active metabolites of cyclophosphamide and ifosfamide in rhesus monkeys.

The penetration of the active metabolites of cyclophosphamide (CP) and ifosfamide (IF) into cerebrospinal fluid (CSF) was determined in rhesus monkeys following an i.v. infusion of 1 gm/m2 of CP and IF. Active metabolites were measured using a high-performance liquid chromatography assay with fluorometric detection following derivatization with m-aminophenol. CSF to blood ratios of the active metabolites of CP and IF were found to be 0.17 and 0.13 following systemic dosing of CP and IF, respectively. The levels achieved in the CSF, however, were equivalent to levels known to be cytocidal to malignant cell lines derived from tumors which metastasize to the central nervous system. Only one animal demonstrated neurotoxicity with IF. CSF levels of active metabolite in this animal were similar to those observed in the other animals.

Cyclophosphamide and ifosfamide metabolites in the cerebrospinal fluid of children.

Although both cyclophosphamide (CP) and ifosfamide (IF) are used in the treatment of central nervous system tumors, little is known about the concentration of either drug or their metabolites in the cerebrospinal fluid (CSF) of children. The concentrations of the parent oxazaphosphorine and its principal metabolites were measured simultaneously in the plasma and CSF of 25 children. Twenty-one patients received CP for the treatment of either acute lymphoblastic leukemia, non-Hodgkin's lymphoma, or medulloblastoma, and 4 children received IF for the treatment of rhabdomyosarcoma. A high degree of interpatient variation was seen in terms of the CSF concentration of CP and the CSF:plasma ratio. The CSF:plasma ratio was greater for IF than for CP (P < 0.001). In contrast to IF, where the majority of metabolites was measured in the CSF, no child receiving CP had detectable metabolites. Children receiving dexamethasone had lower concentrations of CP in the CSF (P = 0.04). The CSF:plasma ratio for isophosphoramide mustard was greater than that for either parent drug or any other metabolite. These results demonstrate that IF enters the CSF to a greater extent than CP in children. The ability of both IF and CP and their metabolites to cross the blood-brain barrier may be reduced by dexamethasone.

Cyclophosphamide plasma and cerebrospinal fluid kinetics with and without dimethyl sulfoxide.

Ten patients with brain tumors and indwelling ventricular reservoirs were pretreated with 5% to 10% dimethyl sulfoxide (DMSO) (intravenous, oral, or both) and were then treated with 1.0 to 1.25 gm/m2 cyclophosphamide (CYC). All patients were also on anticonvulsants and dexamethasone. CYC and alkylating activity (alk act) in plasma and concomitant ventricular cerebrospinal fluid (CSF) were measured by gas chromatography and p-nitrobenzyl pyridine assay. CYC entered the CSF without difficulty and was lost from CSF more slowly than from plasma. Alk act did not enter CSF as well as did CYC. DMSO did not alter any measured aspect of CYC or alk act disposition. Specifically, it did not alter the CYC plasma half-life (t1/2), CSF t1/2, peak CSF: peak plasma CYC concentration ratio, or the urinary excretion of CYC. DMSO did not alter the plasma t1/2 or urinary excretion of alk act or the peak CSF:peak plasma concentration ratio of alk act. Our data show reduced plasma t1/2 of CYC and increased plasma and urinary alk act. This may reflect tht effect of long-term therapy with anticonvulsants or steroids.

Determination of cyclophosphamide in urine, serum and cerebrospinal fluid of multiple sclerosis patients by field desorption mass spectrometry.

The levels of cyclophosphamide in samples of urine, serum and cerebrospinal fluid of multiple sclerosis patients, who had received the drug orally (4 x 100 mg/day) have been determined by field desorption mass spectrometry using the principle of stable isotope dilution. After thorough preparation of the samples, concentrations of cyclophosphamide of 10 to 60 micrograms/ml in urine and 200 to 400 ng/ml in serum and cerebrospinal fluid have been determined from 0.6-3 ml samples. The first quantitative data for cyclophosphamide in cerebrospinal fluid of multiple sclerosis patients could be established without the use of radioactive material. The relatively high level of the parent drug found in the fluid at the end of a 3-weeks treatment may shed some light on the mechanism of action of this drug in the treatment of the disease.

[Effect of high-dose cyclophosphamide plus high-dose etoposide in malignant brain tumors of children followed by autologous bone marrow rescue].

Four pediatric patients with malignant brain tumors were treated with very high-dose etoposide plus very high-dose cyclophosphamide (HD-VP 16/CPM) followed by autologous bone marrow rescue. There were two brain stem gliomas, which were refractory to radiation therapy, ACNC, and beta-interferon and two relapsed malignant brain tumors. Both of the two with brain stem gliomas achieved response, one with clinical improvement and decrease of tumor size on CT scanning, the other with clinical improvement. Overall response duration was three months and nine months. Two patients with relapsed brain tumors received HD-VP 16/CPM as adjuvant chemotherapy. Low but significant levels of VP 16 and CPM were detected in CSF. Further investigation of HD-VP 16/CPM is needed as a chemotherapy for malignant brain tumors in children.