Generation of clinical grade CD19-specific CAR-modified CD8+ memory stem cells for the treatment of B-cell malignancies

Long-lived, self-renewing, multipotent T memory stem cells (TSCM) can trigger profound and sustained tumor regression but their rareness poses a major hurdle to their clinical application. Presently, clinically compliant procedures to generate relevant numbers of this T cell population are undefined. Here, we provide a strategy for deriving large numbers of clinical grade tumor-redirected TSCM cells starting from nave precursors. CD8+CD62L+CD45RA+ nave T cells enriched by streptamer-based serial positive selection were activated by CD3/CD28 engagement in the presence of IL-7, IL-21 and the glycogen synthase-3 inhibitor TWS119, and genetically engineered to express a CD19-specific chimeric antigen receptor (CD19-CAR). These conditions allowed for the generation of CD19-CAR modified TSCM cells that were phenotypically, functionally and transcriptomically equivalent to their naturally occurring counterpart. Compared with T cell products currently under clinical investigation, CD19-CAR modified TSCM cells exhibit enhanced metabolic fitness, persistence and anti-tumor activity against systemic acute lymphoblastic leukemia xenografts. Based on these findings, we have initiated a phase 1 clinical study to evaluate the activity of CD19-CAR modified TSCM in patients with B-cell malignancies refractory to prior allogeneic hematopoietic stem cell transplantation.

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Sabatino M, Hu J, Sommariva M, Gautam S, Fellowes V, Hocker JD, Dougherty S, Qin H, Klebanoff CA, Fry TJ, Gress RE, Kochenderfer JN, Stroncek DF, Ji Y, Gattinoni L