CD19 Targeted Cord Blood Derived T Cells for Cancer Immunotherapy.

Abstract 3767

Transplantation of unrelated umbilical cord blood (CB) derived stem cells is often used to treat adult patients with B-cell acute lymphoblastic leukemia (B-ALL). However, many patients relapse and overall prognosis is poor. We hypothesize that additional therapy involving adoptive transfer of CB derived T cells modified to express a CD19-specific chimeric antigen receptor (CAR) could improve patient outcome following allogeneic CB transplant. To this end, we have previously demonstrated that human T cells which express the anti-CD19 19–28ζ CAR, containing the signaling domains of the co-stimulatory CD28 receptor and CD3ζ chain, effectively eradicate CD19⁺ tumors both in vitro as well as in vivo in SCID-Beige mice. Herein, we demonstrate the ability to effectively isolate and expand T cells from CB samples using magnetic beads coated with agonistic CD3 and CD28 antibodies (Invitrogen) and comparing subsequent T cell expansions in in vitro cultures with varying additions of exogenous stimulatory cytokines, including IL-2, a combination of IL-2 and IL-7, IL-12 or IL-15. We demonstrate that in vitro culture in the context of exogenous IL-12 (10 ng/ml) resulted in optimal expansion of CB T cells (150-fold). In addition, expansion of T cells in the context of exogenous IL-12 resulted in a favorable phenotype for adoptive cell transfer, with T cells expressing high levels of Granzyme B and Perforin while retaining a “memory” phenotype as assessed by persistent expression of CD62L. This combination of cytotoxic and memory phenotype is optimal for adoptive cell therapy. T cells expanded in this manner were subsequently efficiently retrovirally transduced to express the 19–28ζ CAR. The resulting CD19-specific CB derived T cells were able to specifically lyse CD19⁺ tumor targets as assessed by standard ⁵¹Cr release cytotoxicity assays. We are currently investigating the in vivo anti-tumor function of these modified cells in our previously established preclinical SCID-Beige mouse tumor model and ultimately plan to conduct a Phase 1 clinical trial with these modified T cells in patients with B-ALL undergoing CB transplant.