Results of a phase II study of 506U78 in cutaneous T-cell lymphoma and peripheral T-cell lymphoma: CALGB 59901.

Nelarabine (compound 506U78), a novel purine nucleoside, is a soluble pro-drug of 9-beta-D-arabinofuranosylguanine (ara-G). Nelarabine is rapidly demethoxylated in blood by adenosine deaminase to ara-G. Pre-clinical and clinical studies have demonstrated the selective cytotoxicity of ara-G to T-lineage derived cells. CALGB Protocol 59901 was a Phase II study of nelarabine in patients with systemically untreated cutaneous T-cell lymphoma (CTCL) or refractory/relapsed systemic T-cell lymphoma (STCL). The objectives were to determine response rate, remission duration and safety profile associated with nelarabine given at 1.5 g m(-2) per day on days 1, 3 and 5 as an intravenous infusion every 21 days for a minimum of two cycles and to continue up to two cycles beyond CR up to a maximum of eight cycles. Nineteen patients were enrolled in the study: 11 CTCL and eight STCL patients. Grade 3 or 4 adverse events were documented in 50% and 28%, respectively. In particular, 33% of patients experienced Grade 3 or 4 neurologic toxicities. There were two partial remissions lasting 3 months and 5.5 months, respectively. Median event-free survival was 1.2 months and median overall survival was 3 months. Due to lack of efficacy and excessive toxicity, nelarabine is not recommended as monotherapy in adult patients with CTCL and STCL at this dose schedule.