Phase II trial with sequential clofarabine and cyclophosphamide for refractory and relapsed philadelphia-negative adult acute lymphoblastic leukemia. Results of the GIMEMA LAL 1610 protocol.

Clofarabine (CLO) and cyclophosphamide (CY) combinations were tested in late stage refractory/relapsed (R/R) acute lymphoblastic leukemia (ALL) with disappointing results and high-grade toxicity. We designed a sequential 5-day combination of CLO 40 mg/m2/d plus CY 400 mg/m2/d as first salvage for Philadelphia-negative ALL patients refractory or relapsed until 24 months from complete remission (CR). Primary endpoint was an overall response rate (ORR) ≥ 40%. Among 26 study patients (median age 40.5 years) ORR was 57.6% (CR with complete [n = 8] or incomplete [n = 7] hematologic recovery). Despite severe myelotoxicity, no dose-limiting toxicity suggested de-intensification of CLO schedule. With a median follow-up of 17.0 months, median and 1-year overall and disease-free survival were 6.5 months and 28.6%, and 3.7 months and 28.1%, respectively. This association was tolerable and more effective in patients younger than 40 years with B-precursor ALL, longer first CR, not previously transplanted and achieving CR with full hematological recovery.