Introduction
Nelarabine is a water-soluble prodrug of the cytotoxic deoxyguanosine analog ara-G, to which it is rapidly converted in vivo by adenosine deaminase. Nelarabine has shown activity in the treatment of T-cell malignancies, especially T-cell acute lymphoblastic leukemia. Preliminary data suggested that nelarabine might penetrate into the CSF. We therefore studied the CSF penetration of nelarabine and ara-G in a nonhuman primate model that has been highly predictive of anticancer drug distribution in humans.
Methods
Nelarabine (35 mg/kg, ∼700 mg/m2) was administered over 1 h through a surgically implanted central venous catheter to four nonhuman primates. Blood (four animals) and ventricular CSF (three animals) samples were obtained at intervals for 24 h for determination of nelarabine concentrations, which were measured by HPLC-mass spectrometry.
Results
The nelarabine plasma AUC (median ± s.d.) was 2,820 ± 1,140 μM min and the ara-G plasma AUC was 20,000 ± 8,100 μM min. The terminal half-life of nelarabine in plasma was 25 ± 5.2 min and clearance was 42 ± 61 ml/min/kg. The terminal half-life of ara-G in plasma was 182 ± 45 min. In CSF the terminal half-life of nelarabine was 77 ± 28 min and of ara-G was 232 ± 79 min. The AUCcsf:AUCplasma was 29 ± 11% for nelarabine and 23 ± 12% for ara-G.
Conclusion
The excellent CSF penetration of nelarabine and ara-G supports further study of the contribution of nelarabine to the prevention and treatment of CNS leukemia.