Nelarabine is a purine nucleoside analog and DNA synthesis inhibitor with IC50 from 0.067-2.15 μM in tumor cells.
The IC50 of Nelarabine is 25-fold and 113-fold higher than ARAC in T- and B-lineage, respectively. T-ALL cells are eightfold more sensitive to Nelarabine than B-lineage but there is considerable overlap. The efficacy of NEL in T-lineage and B-lineage cell lines is 25-fold and 113-fold less than ARAC, respectively.  Nelarabine acts by inhibiting DNA synthesis and inducing apoptosis in susceptible cells. Nelarabine demonstrated significant antineoplastic activity with acceptable toxicity. The Nelarabine plasma AUC is 2.82 mM minutes and the ara-G plasma AUC is 20 mM minutes. The terminal half-life of Nelarabine in plasma is 25 min, clearance is 42 mL/minutes/kg, and central volume of distribution is 1.1 L/kg. The terminal half-life of ara-G in plasma is 182 minutes and the central volume of distribution is 1.4 L/kg. In CSF the terminal half-life of Nelarabine is 77 minutes and of ara-G is 232 minutes. The AUCcsf:AUCplasma is 29 % for Nelarabine and 23 % for ara-G. Nelarabine and ara-G do not accumulate with daily infusions because of their relatively short half-lives.