A Study of Fludarabine Dosing in Children and Young Adults With B-cell Acute Lymphoblastic Leukemia

Inclusion Criteria

• •Patients with B-ALL and eligible to receive commercial tisagenlecleucel.
• •Patient's weight \> 9 kg at time of lymphodepleting chemotherapy
• •Adequate organ function at time of LD is required and is defined:
• •* Hepatic: Serum bilirubin ≤ 2 mg/dL, unless benign congenital hyperbilirubinemia
• •* Hepatic: AST and ALT \< 5x the upper limit of normal for age, unless thought to be leukemic disease-related
• •* Renal: Calculated glomerular filtration rate (GFR) ≥ 70 ml/min/1.73m\^2. (based on Schwartz formula GFR (mL/min/1.73 m²) = (36.2 × Height in cm) / Creatinine in μmol/L
• •* Cardiac: LVEF ≥ 50% by multi-gated acquisition scan (MUGA), resting echocardiogram, or cardiac magnetic resonance imaging (MRI) within 6 weeks of screening
• •* Pulmonary: Oxygen saturation as recorded by pulse oximetry of ≥ 90% on room air
• •Adequate performance status:
• •* Age ≥ 16 years: ECOG ≤ 1 or Karnofsky \> 60% at treatment
• •* Age \< 16 years: Lansky ≥ 60% at treatment
• •Willing to participate as research subject and provide written informed consent from parents/legal representative, patient, and age-appropriate assent as appropriate before any study specific screening procedures are conducted, according to local, regional or national law and legislation.