CD19 /22 CAR T Cells (AUTO3) for the Treatment of B Cell Acute Lymphoblastic Leukemia (ALL)

Key Inclusion Criteria: 1. Male or female patients aged 1-24 years with high risk (HR) relapsed/refractory B-lineage ALL, AND: 1. Any bone marrow (BM) relapse or central nervous system (CNS) relapse with detectable BM disease after allogeneic stem cell transplant (SCT) and must be ≥6 months from SCT at the time of AUTO3 infusion; OR, 2. HR first relapse; OR, 3. Standard risk relapse patients with HR cytogenetics; OR, 4. Second or greater relapse; OR, 5. BM minimal residual disease (MRD) ≥10-³ prior to planned SCT; OR, 6. Any on-treatment relapse in patients aged 16-24 years. (Phase II Only - Criteria in addition to those described above:) 7. Primary refractory disease; OR, 8. Patients with Philadelphia chromosome positive ALL are eligible if they are intolerant to or have failed 2 lines of tyrosine kinase inhibitor (TKI) therapy, or if TKI therapy is contraindicated; OR, 9. Isolated CNS relapse but with ≤CNS Grade 2 disease at time of enrolment. 2. Documentation of CD19 and or CD22 expression on leukaemic blasts in the BM, peripheral blood, or cerebrospinal fluid within 3 months of screening. 3. Detectable disease in the BM at a level ≥10-⁴ (Phase I only). 4. Absolute lymphocyte count ≥0.5 x 10⁹/L. 5. Adequate renal, hepatic, pulmonary, and cardiac function. 6. Karnofsky (age ≥10 years) or Lansky (age \<10 years) score ≥50%. 7. Willing and able to give written, informed consent to the current study (patient and/or parent or legal guardian). Exclusion Criteria: 1. Isolated extra-medullary disease relapse. 2. Active CNS involvement of ALL (CNS Grade 3 per National Comprehensive Cancer Network guidelines). 3. Active infectious bacterial or viral disease requiring IV anti-microbials for treatment. 4. Females who are pregnant or lactating. 5. Females of child-bearing potential and post pubertal male participants who are unwilling to use highly effective methods of contraception for a period of 1 year after the AUTO3 infusion. 6. Inability to tolerate leukapheresis. 7. Prior CD19 or CD22 targeted therapy with Grade 4 toxicity or ≥refractory Grade 3 cytokine release syndrome (CRS) or ≥Grade 3 drug related CNS toxicity. 8. Pre-existing significant neurological disorder. 9. Stem Cell Transplant patients only: active significant acute graft versus host disease (GVHD) or moderate/severe chronic GVHD requiring systemic steroids or other immunosuppressant within 4 weeks of enrolment. 10. The following medications are excluded: 1. Steroids: Therapeutic doses of steroids must be stopped \>72 hours prior to AUTO3 infusion and leukapheresis. However, physiological replacement doses of steroids are allowed: \<12 mg/m2/day hydrocortisone or equivalent. 2. Allogeneic cellular therapy: Any donor lymphocyte infusions must be completed \>6 weeks prior to AUTO3 infusion. 3. Graft versus host disease therapies: Any drug used for GVHD must be stopped \>4 weeks prior to AUTO3 infusion. 4. Chemotherapy: Should be stopped 1 week prior to leukapheresis and 2 days prior to starting pre-conditioning chemotherapy. 11. Known allergy to albumin, dimethyl sulfoxide, cyclophosphamide or fludarabine. For AUTO3 Infusion: Patients meeting any of the following exclusion criteria will not be treated with AUTO3 or treatment will be delayed until they no longer meet these criteria: 1. Severe intercurrent infection. 2. Requirement for supplementary oxygen. 3. Allogeneic transplant recipients with active significant acute GVHD overall Grade ≥II or moderate/severe chronic GVHD requiring systemic steroids.