Drug Groups

approved; investigational

Description

Nelarabine is a chemotherapy drug used in T-cell acute lymphoblastic leukemia. Nelarabine is a purine nucleoside analog converted to its corresponding arabinosylguanine nucleotide triphosphate (araGTP), resulting in inhibition of DNA synthesis and cytotoxicity.

Indication

For the treatment of pediatric and adult patients with acute T-cell lymphoblastic leukemia and T-cell lymphoblastic lymphoma whose disease has not responded to or has relapsed following treatment with at least two chemotherapy regimens.

Pharmacology

Nelarabine is a prodrug of the cytotoxic deoxyguanosine analogue 9-ß-D-arabinofuranosylguanine (ara-G). Nelarabine is demethylated by adenosine deaminase (ADA) to ara-G. Ara-G is then transported into cells, where it undergoes three phosphorylation steps, resulting in the formation of ara-G triphosphate (ara-GTP). In the first phosphorylation step, ara-G is converted to ara-G monophosphate (ara-GMP). Ara-GMP is then monophosphorylated by deoxyguanosine kinase and deoxycytidine kinase to ara-G diphosphate, and then subsequently to the active ara-G triphosphate (ara-GTP). Ara-GTP is the one that exerts the pharmacological effect. Pre-clinical studies suggest that T-cells are particularly sensitive to nelarabine.

Toxicity

A single IV dose of 4,800 mg/m^2 was lethal in monkeys, and was associated with CNS signs including reduced/shallow respiration, reduced reflexes, and flaccid muscle tone. It is anticipated that overdosage would result in severe neurotoxicity (possibly including paralysis, coma), myelosuppression, and potentially death.

Affected Organisms

Biotransformation

The principal route of metabolism for nelarabine is O-demethylation by adenosine deaminase to form ara-G, which undergoes hydrolysis to form guanine. In addition, some nelarabine is hydrolyzed to form methylguanine, which is O-demethylated to form guanine. Guanine is N-deaminated to form xanthine, which is further oxidized to yield uric acid. Ring opening of uric acid followed by further oxidation results in the formation of allantoin.

Half Life

Nelarabine and ara-G are rapidly eliminated from plasma with a half-life of approximately 30 minutes and 3 hours.

Protein Binding

Nelarabine and ara-G are not substantially bound to human plasma proteins (<25%) in vitro, and binding is independent of nelarabine or ara-G concentrations up to 600 mM.

Elimination

Excretion: Nelarabine and ara-G are partially eliminated by the kidneys.

Clearance

* 197? +/- ?189 L/h/m2 [Adult patients with refractory leukemia or lymphoma receiving doses of 199 to 2,900 mg/m2]
* 259? +/- ?409 L/h/m2 [Pediatric patients with refractory leukemia or lymphoma receiving doses of 104 to 2,900 mg/m2]

References

External Links