Treatment with Humanized Selective CD19CAR-T Cells Shows Efficacy in Highly Treated B-ALL Patients Who Have Relapsed after Receiving Murine-Based CD19CAR-T Therapies

Purpose: CD19 chimeric antigen receptor (CAR)-T therapy has shown impactful results in treatment of B-cell malignancies. However, immune recognition of the murine scFv may render subsequent infusion(s) ineffective. Also, nonselective expansion of both CAR-transduced and nontransduced T cells during the production stage affects the yield and purity of final products. Here, we aim to develop a humanized selective (hs) CD19 CAR to solve the above problems. Experimental Design: A CD19 hsCAR was designed, which incorporated a short selective domain between the humanized heavy chain and light chain. The CAR was examined for its property, and then trialed in 5 highly treated B-ALL patients. Results: hsCAR possessed around 6-fold higher affinity to CD19 versus murine CAR (mCAR). Incubation with selective domain-specific mAbs (SmAb) selectively expanded CAR-transduced T cells, and led to a higher proportion of central memory T cells in the final products. SmAb-stimulated CD19 hsCAR-T cells exhibited superior antitumor cytotoxic functions in vitro and in vivo. Autologous (n = 2) and allogeneic donor (n = 3, with hematopoietic stem cell transplantation) hsCAR-T cells were infused into 5 patients who had relapsed after receiving mCAR-T treatments. Two patients received mCAR-T treatments twice previously but the second treatments were ineffective. In contrast, subsequent hsCAR-T treatments proved effective in all 5 patients and achieved complete molecular remission in four, including one with extramedullary disease with central nervous system involvement. Conclusions: hsCD19 CAR-T treatment shows efficacy in highly treated B-ALL patients who have relapsed after receiving CD19 mCAR-T therapies.