Phase 2 open-label study of MEDI-551 and bendamustine versus rituximab and bendamustine in adults with relapsed or refractory CLL.

3028 Background: Patients (pts) with relapsed/refractory (RR) chronic lymphocytic leukemia (CLL) need therapies that induce prolonged disease control. MEDI-551, an affinity-optimized anti-CD19 antibody, destroys CLL cells by antibody-dependent cellular cytotoxicity. A phase 2 randomized, open-label study (NCT01466153) is evaluating the clinical activity and safety/tolerability of 2 doses of MEDI-551 + bendamustine compared to rituximab + bendamustine in RR CLL patients. Methods: Pts were initially randomized to receive bendamustine + MEDI-551 2 or 4 mg/kg or rituximab (R). Safety assessments include adverse events (AEs) and laboratory parameters. Disease response was determined using 2008 International Working Group criteria. Results: The safety population comprised 124 pts across all arms. Median age was 66y (range 41–81); with deletion (del) (17p): 9%, del (11q): 22%, del (13q): 31%, trisomy 12: 11%. Median number of treatment cycles: 4 (range 1–6). The most common (≥20%) treatment-related AEs with MEDI...