LAUSR

Blinatumomab, a bi‐specific T‐cell engaging CD3‐CD19 antibody construct, has shown significant activity in patients with relapsed/refractory (R/R) B‐cell acute lymphoblastic leukemia (ALL). Despite this improvement, most patients relapse. Here, we describe the outcome of 68 patients with R/R ALL after failure of blinatumomab therapy: 38 (56%) blinatumomab refractory; 30 (44%) relapsing after initial response. After a median follow‐up of 49 months, 9 (13%) patients remained alive. The median overall survival after blinatumomab failure was 5.2 months. At the time of failure, among 61 patients evaluated for immunophenotype, 56 (92%) had CD19‐positive blasts; only five (8%) had ALL recurrence with CD19‐negative disease. Two patients progressed with lower CD19 expression. In summary, the outcome of patients with R/R ALL after blinatumomab failure is poor and treatment of these patients remains an unmet medical need. Our findings indicate that blinatumomab therapy would not exclude a significant number of patients from the potential benefit of subsequent CD19‐directed therapies such as chimeric antigen receptor T‐cell therapy.