Treatment Outcome of Pediatric B-ALL with Bone Marrow and Extramedullary
Relapse by Anti-CD19 CAR-T
Abstract
Background: Anti-CD19 Chimeric Antigen Receptor T-Cell Immunotherapy
(19CAR-T) has achieved impressive clinical achievements in both adult
and pediatric relapsed/refractory (r/r) B-lineage acute lymphoblastic
leukemia (B-ALL). However, the application and effect of CAR-T therapy
in B-ALL patients with extramedullary relapse are rarely issued even
disqualified in some clinical trials. Here, we examined the efficacy of
19CAR-T in patients with both bone marrow and extramedullary
involvement. Methods: CAR-T cells were generated by a lentiviral vector
transfection into primary human T lymphocytes to express anti-CD19 and
anti-CD22 single chain antibody fragments (scFvs) with the cytoplasmic
domains of 4-1BB and CD3ζ. Patients diagnosed as r/r B-ALL with
extramedullary origination were infused with anti-CD19 CAR-T cells. The
clinical responses were evaluated by bone marrow aspiration, imaging,
and flow cytometry examination. Results: A total of 8 patients received
19CAR-T infusion and all of them acquired complete remission (CR), in
which only 1 patient was bridged to hematopoietic stem cell
transplantation (HSCT). Even though there were 3 patients relapsed after
infusion, they received 19/22CAR-T infusion sequentially and acquired
the second remission. To date, 5 patients are continuous CR, and all
patients are still alive. The mean follow-up time was 21.9 months while
the 24-month estimated event-free survival (EFS) is 51.4%. Conclusions:
Anti-CD19 CAR-T therapy can lead to clinical remission for
extramedullary relapsed pediatric B-ALL patients. However, the problem
of CD19+ relapses after CAR-T remained to be solved. For patients
relapsing after CAR-T, the second CAR-T therapy suggests creating
another opportunity of remission for subsequent HSCT.