Clinical course relative to in vivo CAR T-cell persistence and B-cell recovery in CR/CRi patients after JCAR021 data from 14 patients in CR/CRi after JCAR021 treatment. Black horizontal bars, follow-up duration. Due to severe leukocytosis, patient ALL-HMB-3 had ≤1% B cells in a CD45⁺ leukocyte gate at the time of relapse, but a B-cell count of 94/μL, indicating B-cell recovery had occurred.