Inclusion Criteria:

          1. CD19 expressing B-cell Acute Lymphoblastic Leukemia

          2. De novo NCI HR B-ALL who received first-line treatment and are MRD ≥ 0.01% at EOC. EOC
             bone marrow MRD will be collected prior to screening and will be assessed by
             multi-parameter flow cytometry using central laboratory analysis.

          3. Age 1 to 25 years at the time of screening

          4. Lansky (age < 16 years) or Karnofsky (age ≥ 16 years) performance status ≥ 60%

          5. Adequate organ function during the screening period:

             A. Renal function based on age/gender B. ALT ≤ 5 times ULN for age C. AST ≤ 5 times
             ULN for age D. Total bilirubin < 2 mg/dL (for Gilbert's Syndrome subjects total
             bilirubin < 4 mg/dL)

             E. Adequate pulmonary function defined as:

               -  no or mild dyspnea (≤ Grade 1)

               -  oxygen saturation of > 90% on room air F. Adequate cardiac function defined as
                  LVSF ≥ 28% confirmed by echocardiogram or LVEF ≥ 45% confirmed by echocardiogram
                  or MUGA within 6 weeks of screening

          6. Prior induction and consolidation chemotherapy allowed: 1st line subjects: ≤ 3 blocks
             of standard chemotherapy for first-line B-ALL, defined as 4-drug induction,
             Berlin-Frankfurt-Münster (BFM) consolidation or Phase 1b, and interim maintenance with
             high-dose methotrexate.

        Exclusion Criteria:

          1. M3 marrow at the completion of 1st line induction therapy

          2. M2 or M3 marrow or persistent extramedullary disease at the completion of first-line
             consolidation therapy or evidence of disease progression in the peripheral blood or
             new extramedullary disease prior to enrollment. Patients with previous CNS disease are
             eligible if there is no active CNS involvement of leukemia at the time of screening.

          3. Philadelphia chromosome positive ALL

          4. Hypodiploid: less than 44 chromosomes and/or DNA index < 0.81, or other clear evidence
             of a hypodiploid clone

          5. Prior tyrosine kinase inhibitor therapy

          6. Subjects with concomitant genetic syndromes associated with bone marrow failure
             states: such as subjects with Fanconi anemia, Kostmann syndrome, Shwachman syndrome or
             any other known bone marrow failure syndrome. Subjects with Down syndrome will not be
             excluded.

          7. Subjects with Burkitt's lymphoma/leukemia (i.e. subjects with mature B-ALL, leukemia
             with B-cell [sIg positive and kappa or lambda restricted positivity] ALL, with FAB L3
             morphology and /or a MYC translocation)

          8. Has had treatment with any prior anti-CD19 therapy 9. Treatment with any prior gene or
             engineered T cell therapy

        Other protocol-defined inclusion/exclusion may apply.