Blinatumomab, a new agent designed to treat acute lymphoblastic leukemia, is in Phase III trials. The drug enables CD3-positive T cells to recognize and eliminate CD19-positive acute lymphoblastic leukemia (ALL) blasts. A new study assigned 405 adults with heavily pretreated B-cell precursor ALL, in a 2:1 ratio, to receive either blinatumomab or standard-of-care chemotherapy. The median overall survival was 7.7 months in the blinatumomab group and 4.0 months in the chemotherapy group (hazard ratio for death with blinatumomab vs. chemotherapy, 0.71; 95% CI, 0.55-0.93; P = 0.01). Along with improved survival, remission rates and event-free survival were significantly higher in the blinatumomab group. About one-quarter of both treatment groups underwent allogeneic stem cell transplantation. Adverse events were lower with blinatumomab. Treatment with blinatumomab resulted in significantly longer overall survival than chemotherapy among adult patients with relapsed or refractory B-cell precursor ALL. (N Engl J Med 2017;376:836-847)