In patients with acute lymphoblastic leukaemia (ALL) who achieve haematological complete remission, the presence of minimal residual disease (MRD) enables the prediction of disease relapse. In an open-label single-arm study, 113 adults with B cell ALL received up to four cycles of blinatumomab, a bispecific T cell-engager antibody construct that directs T cells to CD19-positive cells. Patients could undergo allogeneic haematopoietic stem cell transplantation any time after cycle 1. A complete MRD response, the primary end point, was achieved in 78% of the patients, who had longer relapse-free survival and overall survival durations than those who did not achieve a complete MRD response: 23.6 months and 38.9 months, respectively, versus 5.7 months and 12.5 months. Grade 3 and 4 neurological adverse events were reported in 10% and 3% of patients, respectively, and cytokine-release syndrome in 3%.