A novel generation 1928zT2 CAR T cells induce remission in extramedullary relapse of acute lymphoblastic leukemia

Anti- CD19 chimeric antigen receptor(CAR) T cells have shown promise in the treatment of B cell acute lymphocytic leukemia(B-ALL). However, its efficacy in B-ALL patients with extramedullary involvement is limited due to poor responses and neurotoxicity. Here, we utilized a third generation of CAR T cell vector, which contains the Toll/ interleukin-1 receptor(ITR) domain of Toll-like receptor 2 ( TLR2), to generate 1928zT2 T cells targeting CD19, and evaluated the efficacy of 1928zT2 T cells in relapse or refractory B-ALL patients with extramedullary involvement. 1928zT2 T cells were generated by 19-28z- TLR2lentiviral vector transfection into primary human T lymphocytes. The anti-leukemia effect of 1928zT2 T cells were determined by killing assays and in xenografts. Three patients diagnosed as relapse or refractory ALL with extramedullary involvement were infused with 1928zT2 T cells, and the clinical responses were evaluated by BM smear, B-ultrasonography, PET/CT, histology, flow cytometry, qPCR, ELISA, and luminex assay. 1928zT2 T cells exhibited enhanced effector function against CD19+ leukemic cells in vitro and in a xenograft model of human extramedullary leukemia. Notably, the 1928zT2 T cells eradicated extramedullary leukemia and induced complete remission in the three relapse and refractory ALL patients without serious adverse effects. 1928zT2 T cells expanded robustly in the circulation of these three patients and were detected in the cerebrospinal fluid of patient 3. These three patients experienced cytokine release syndrome(CRS) with grade 2 or 3, which remitted spontaneously or after tocilizumabtreatment. None of the three patients suffered neurotoxicity or needed further intensive care. Our results demonstrate that 1928zT2 T cells with TLR2incorporation augment anti-leukemic effects, particularly for eradicating extramedullary leukemia cells, and suggest that the infusion of 1928zT2 T cells is an encouraging treatment for relapsed/refractory ALL patients with extramedullary involvement. ClinicalTrials.gov identifier NCT02822326 . Date of registration: July 4, 2016.