RecruitingEarly Phase 1Drug trialIomab-ACT: A Pilot Study of 131-I Apamistamab Followed by CD19-Targeted CAR T-Cell Therapy for Patients With Relapsed or Refractory B-Cell Acute Lymphoblastic Leukemia or Diffuse Large B-Cell LymphomaThis is a pilot study; patients will receive 131-I apamistamab prior to CAR T-cell infusion in order to determine the maximum tolerated dose of 131-I apamistamab is exceeded at 75 mCi, and if so, to assess the safety of a step-down dose of 50 mCi.