Nelarabine: a novel purine antimetabolite antineoplastic agent.
BACKGROUND
Nelarabine was approved by the US Food and Drug Administration (FDA) in October 2005 for the treatment of T-cell acute lymphoblastic leukemia (T-ALL) and T-cell lymphoblastic lymphoma (T-LBL) that has not responded to or has relapsed after treatment with at least 2 chemotherapy regimens.


OBJECTIVE
This article reviews the pharmacology, mechanism of action, and pharmacokinetic and pharmacodynamic properties of nelarabine. Also reviewed are nelarabine's clinical efficacy in T-ALL, T-LBL, and other hematologic malignancies; its toxicity profile, dosage, and administration; and areas of ongoing and future research.


METHODS
Relevant literature was identified through searches of MEDLINE (1966-April 2007), International Pharmaceutical Abstracts (1970-April 2007), and the American Society of Hematology database (2003-2006) using the terms nelarabine, Arranon, 506U78, and 2-amino-6-methoxypurine arabinoside. The reference lists of the identified articles were searched for additional sources. Product information obtained from the manufacturer of nelarabine was consulted, as were the FDA reviews of nelarabine. All identified publications were considered, and those meeting the objectives of this review were included.


RESULTS
Nelarabine, a soluble prodrug of 9-beta-D- arabinofuranosylguanine (ara-G), is a novel purine antimetabolite antineoplastic that preferentially accumulates in T-cells. Ara-G is rapidly phosphorylated in T-cells to ara-G triphosphate (ara-GTP), which exerts cytotoxic effects. Renal elimination of ara-G is decreased in patients with mild to moderate renal impairment; however, no dose adjustment is recommended. Accumulation of ara-GTP occurs in T-cells in a dose-dependent manner, leading to preferential cytotoxicity. Nelarabine has activity in T-cell malignancies, as evaluated in 2 Phase I and 5 Phase II studies. It received accelerated approval from the FDA based on the resuits of 2 Phase II trials, one in pediatric patients (PGAA 2001) and the other in adults (CALGB 19801). In PGAA 2001, patients with T-ALL in first relapse (n = 33) had an objective response rate of 55% (16 with a complete response [CR] and 2 with a partial response [PR]), and those with T-ALL in second relapse (n = 30) had an objective response rate of 27% (7 CR and 1 PR). Among patients with central nervous system-positive T-ALL or T-cell non-Hodgkins lymphoma (T-NHL) (n = 21), 33% had an objective response (5 CR and 2 PR); among patients with T-ALL or T-NHL with extramedullary relapse (n = 22), 14% had a PR. CALGB 19801 included 39 adult patients with T-cell malignancies, of whom 7 (18%) had a CR and an additional 2 (5%) had a CR without full hematologic recovery. The recommended dose of nelarabine in adults is 1500 mg/m(2) IV given over 2 hours on days 1, 3, and 5, repeated every 21 days; the recommended dose in pediatric patients is 650 mg/m(2) IV given over 1 hour for 5 consecutive days, repeated every 21 days. Dose-limiting toxicities observed in the Phase I and II trials included central and peripheral neurotoxicity. Symptoms of central neurotoxicity included somnolence, seizures, dizziness, confusion, and ataxia; symptoms of peripheral neurotoxicity included paresthesias, pain in the extremities, and peripheral neuropathy.


CONCLUSIONS
Nelarabine is indicated for the treatment of T-ALL and T-LBL that has not responded to or has relapsed after treatment with at least 2 chemotherapy regimens. Objective response rates in Phase II clinical trials of nelarabine have ranged from 11% to 60%. Use of nelarabine is limited by potentially severe neurotoxicity.
Buie
Larry W
LW
Division of Pharmacotherapy and Experimental Therapeutics, University of North Carolina School of Pharmacy, Chapel Hill, North Carolina 27599, USA. larry_buie@email.unc.edu
Epstein
Stacy S
SS
Lindley
Celeste M
CM
D000964:Antimetabolites, Antineoplastic / Q000008:administration & dosage / Q000009:adverse effects / Q000494:pharmacology / Q000627:therapeutic use*; D001087:Arabinonucleosides / Q000008:administration & dosage / Q000009:adverse effects / Q000494:pharmacology / Q000627:therapeutic use*; D019008:Drug Resistance, Neoplasm; D019337:Hematologic Neoplasms / Q000188:drug therapy*; D006801:Humans; D015459:Leukemia-Lymphoma, Adult T-Cell / Q000188:drug therapy*; D016399:Lymphoma, T-Cell / Q000188:drug therapy*; D011684:Purine Nucleosides / Q000008:administration & dosage / Q000009:adverse effects / Q000494:pharmacology / Q000627:therapeutic use*
D000964:Antimetabolites, Antineoplastic; D001087:Arabinonucleosides; D011684:Purine Nucleosides; C104457:nelarabine