An arabinonucleoside antimetabolite with antineoplastic activity. Nelarabine is demethoxylated by adenosine deaminase to become biologically active 9-beta-D-arabinosylguanine (ara-G); ara-G incorporates into DNA, thereby inhibiting DNA synthesis and inducing an S phase-dependent apoptosis of tumor cells. Check for active clinical trialsusing this agent. or A drug that interferes with the ability of a virus to make copies of itself.