Key Inclusion Criteria:

• Age: 2-21 years
• Relapsed or refractory B-precursor ALL defined as one of the following:
• Primary refractory diseaseFirst relapse if first remission ≤ 12 monthsRelapsed or refractory disease after first or later salvage therapyRelapsed or refractory disease after allogeneic transplant provided subject is at least 100 days from stem cell transplant at the time of enrollmentMorphological disease in the bone marrow (≥ 5% blasts)Subjects with Ph+ disease are eligible if they are intolerant to tyrosine kinase inhibitor (TKI) therapy, or if they have relapsed/refractory disease despite treatment with at least 2 different TKIsIn subjects previously treated with blinatumomab, CD19 tumor expression on blasts obtained from bone marrow or peripheral blood must be documented after completion of the most recent prior line of therapy. If CD19 expression is quantified, then blasts must be ≥ 90% CD19 positive

Key Exclusion Criteria:

• ​Burkitt’s leukemia/lymphoma  or chronic myelogenous leukemia lymphoid blast crisisHistory of malignancy other than nonmelanoma skin cancer or carcinoma in situ (eg, cervix, bladder, breast) unless disease free for at least 3 years
• History of severe hypersensitivity reaction to aminoglycosides or any of the agents used in this study CNS abnormalities:Presence of CNS-3 disease,Presence of CNS-2 disease with neurological changes Note: Subjects with CNS-1  and those with CNS-2 without clinically evident neurological changes are eligible to participate in the study.
• History or presence of any CNS disorder, such as a seizure disorder, cerebrovascular ischemia/hemorrhage, dementia, cerebellar disease, any autoimmune disease with CNS involvement, posterior reversible encephalopathy syndrome (PRES), or cerebral edema
• History of concomitant genetic syndrome associated with bone marrow failure such as Fanconi anemia, Kostmann syndrome, or Shwachman-Diamond syndrome
• History of myocardial infarction, cardiac angioplasty or stenting, unstable angina, or other clinically significant cardiac disease within 12 months of enrollmentHistory of symptomatic deep vein thrombosis or pulmonary embolism within 6 months of enrollment.
• Prior Therapy:Salvage systemic therapy (including chemotherapy, TKIs for Ph+ ALL, and blinatumomab) within 1 week or 5 half-livesPrior CD19 directed therapy other than blinatumomabHistory of Grade 4 neurologic event (Common or Grade 4 CRS  with prior CD19-directed therapy Alemtuzumab within 6 months prior to enrollment, clofarabine or cladribine within 3 months prior to enrollment, or PEG-asparaginase within 3 weeks prior to enrollment oDonor lymphocyte infusion (DLI) within 28 days prior to enrollment oAny drug used for GVHD within 4 weeks prior to enrollmentimmunosuppressive antibody used within 4 weeks prior to enrollment