A Study of CD19 Targeted CAR T Cell Therapy in Pediatric Patients With Relapsed or Refractory B Cell Acute Lymphoblastic Leukemia (B ALL) and Aggressive Mature B-cell Non-Hodgkin Lymphoma (B NHL)

INCLUSION CRITERIA: * \< 18 years old at screening * ≥ 6 kg body weight at screening Pediatric patients with r/r B ALL r/r CD19-positive aggressive mature B including the B NHL subtypes: i) diffuse large B cell lymphoma, ii) Burkitt's lymphoma, iii) primary mediastinal large B cell lymphoma, iv) high-grade B cell lymphoma (not otherwise specified). * Karnofsky (age ≥ 10 years) or Lansky (age \< 10 year) performance status score ≥ 50%. * In participants with B ALL, local documentation of CD19 expression on leukemic blasts in the BM, peripheral blood, or cerebrospinal fluid or biopsy done no more than 30 days prior to consent. * Adequate renal, hepatic, pulmonary, and cardiac function. EXCLUSION CRITERIA: * Diagnosis of chronic myelogenous leukemia in lymphoid blast crisis. * History or presence of clinically relevant central nervous system (CNS) pathology unrelated to CNS leukemia. * Presence of active or uncontrolled fungal, bacterial, viral, or other infection requiring systemic antimicrobials for management. * Received prior (\< 3 months before obe cel infusion) stem cell transplantation. * Prior CD19 targeted therapy other than blinatumomab. * Experienced Grade ≥ 3 neurotoxicity following blinatumomab.