Background and objective: Liposomal cytarabine (DepoCyte) is a slow-release formulation for intrathecal application, ensuring prolonged drug exposure. Although there is an urgent need for new treatment options for infants with leptomeningeal dissemination of a malignant brain tumour, there are no clinical and pharmacokinetic data available on this drug for children aged <3 years. The objective of this pilot study was to determine the feasibility, safety and pharmacokinetics of cytarabine after intrathecal administration of liposomal cytarabine 25 mg in patients aged <3 years.
Patients and methods: Six male patients with a mean age of 21 months and CNS primitive neuroectodermal tumours (n = 3) or atypical teratoid/rhabdoid tumours (n = 3) were included. Liposomal cytarabine (25 mg) was administered intraventricularly. One patient also received the drug by lumbar puncture. Dexamethasone was used concomitantly for 3-5 days to prevent arachnoiditis. Cerebrospinal fluid (CSF) and plasma samples were collected before administration of liposomal cytarabine and 1 hour, 12 hours, 24 hours, 1 week and 2 weeks post-dosing. Noncompartmental pharmacokinetic analysis of CSF and plasma was performed.
Results: Liposomal cytarabine was generally well tolerated; only grade 2 headache occurred in one patient. After intraventricular administration of cytarabine 25 mg, free and encapsulated drug concentrations above the cytotoxic drug level of 0.1 microg/mL were detectable in the CSF for at least 7 days and up to 14 days post-dosing. The average elimination half-lives were 56.7 hours for encapsulated cytarabine and 59.3 hours for free cytarabine. After intralumbar administration, the elimination half-life of free cytarabine, measured in the ventricular CSF during two courses in one patient, was significantly shorter (32.7 hours).
Conclusion: Application of liposomal cytarabine with concomitant dexamethasone appears to be safe and well tolerated in children aged <3 years. Drug exposure in infants aged <3 years after an intraventricular dose of 25 mg is comparable to that after administration of 50 mg in adult patients and 35 mg in older children.