Adults with relapsed/refractory B-cell precursor ALL were randomized in a 2:1 ratio to receive blinatumomab or 1 of 4 pre-specified, investigator-chosen, SOC chemotherapy regimens. Randomization was stratified by age (< 35 years vs ≥ 35 years of age), prior salvage therapy (yes vs no), and prior allogeneic HSCT (yes vs no) as assessed at the time of consent.