Using Oncolytic Virus to Retask CD19-Chimeric Antigen Receptor-T Cells for Treatment of Pancreatic Cancer: Toward a Universal Chimeric Antigen Receptor-T Cell Strategy for Solid Tumors.

BACKGROUND: CAR-T cells targeting the B-cell antigen CD19 are standard therapy for relapsed/ refractory B-cell lymphoma and leukemia. CAR-T cell therapy in solid tumors is limited due to an immunosuppressive tumor microenvironment (TME) and a lack of tumor-restricted antigens. We recently engineered an oncolytic virus (CF33) with high solid tumor affinity and specificity to deliver a non-signaling truncated CD19 antigen (CD19t), allowing targeting by CD19-CAR-T cells. Here, we tested this combination against pancreatic cancer.

STUDY DESIGN: We engineered CF33 to express a CD19t (CF33-CD19t) target. Flow cytometry and ELISA were performed to quantify CD19t expression, immune activation, and killing by virus and CD19-CAR-T cells against various pancreatic tumor cells. Subcutaneous pancreatic human xenograft tumor models were treated with virus, CAR-T cells, or virus+CAR-T cells.

RESULTS: In vitro, CF33-CD19t infection of tumor cells resulted in >90% CD19t cell-surface expression. Co-culturing CD19-CAR-T cells with infected cells resulted in IL-2 and IFN-γ secretion, upregulation of T cell activation markers, and synergistic cell killing. Combination therapy of virus+CAR-T cells caused significant tumor regression (Day 13): control (n=16, 485 ± 20 mm 3), virus alone (n=20, 254 ± 23 mm 3, P=0.0001), CAR-T cells alone (n=18, 466 ± 25 mm 3, P=NS) virus+CAR-T cells (n=16, 128 ± 14 mm 3, P<0.0001 vs. control; P=0.0003 vs. virus).

CONCLUSIONS: Engineered CF33-CD19t effectively infects and expresses CD19t in pancreatic tumors, triggering cell killing and increased immunogenic response by CD19-CAR-T cells. Notably, CF33-CD19t can turn cold immunologic tumors hot, enabling solid tumors to be targetable by agents designed against liquid tumor antigens.