Donor derived CAR19 T-cells (National Health & Medical Research Council)

Chimeric antigen receptor (CAR)‐positive cell therapy, specifically with anti‐CD19 CAR‐T (CAR19‐T) cells, achieves a high complete response during tumor treatment for hematological malignancies. Large‐scale production and application of CAR‐T therapy can be achieved by developing efficient and low‐cost enrichment methods for CAR‐T cells, expansion monitoring in vivo, and overcoming tumor escape. Here, novel CAR‐specific binding aptamers (CAR‐ap) to traceless sort CAR‐positive cells and obtain a high positive rate of CAR19‐T cells is identified. Additionally, CAR‐ap‐enriched CAR19‐T cells exhibit similar antitumor capacity as CAR‐ab (anti‐CAR antibody)‐enriched CAR‐T cells. Moreover, CAR‐ap accurately monitors the expansion of CAR19‐T cells in vivo and predicts the prognosis of CAR‐T treatment. Essentially, a novel class of stable CAR‐ap‐based bispecific circular aptamers (CAR‐bc‐ap) is constructed by linking CAR‐ap with a tumor surface antigen (TSA): protein tyrosine kinase 7 (PTK7) binding aptamer Sgc8. These CAR‐bc‐aps significantly enhance antitumor cytotoxicity with a loss of target antigens by retargeting CAR‐T cells to the tumor in vitro and in vivo. Overall, novel CAR‐aptamers are screened for traceless enrichment, monitoring of CAR‐positive cells, and overcoming tumor cell immune escape. This provides a low‐cost and high‐throughput approach for CAR‐positive cell‐based immunotherapy.

CD19 CAR-T (chimeric antigen receptor-T) cell immunotherapy achieves a remission rate of approximately 70% in recurrent and refractory lymphoma treatment. However, the loss or reduction of CD19 antigen on the surface of lymphoma cells results in the escape of tumor cells from the immune killing of CD19 CAR-T cells (CAR19-T). Therefore, novel therapeutic strategies are urgently required. In this study, an anti-CD79b/CD3 bispecific antibody (BV28-OKT3) was constructed and combined with CAR19-T cells for B-cell lymphoma treatment. When the CD19 antigen was lost or reduced, BV28-OKT3 redirected CAR19-T cells to CD79b⁺ CD19^- lymphoma cells; therefore, BV28-OKT3 overcomes the escape of CD79b⁺ CD19^- lymphoma cells by the killing action of CAR19-T cells in vitro and in vivo. Furthermore, BV28-OKT3 triggered the antitumor function of CAR^- T cells in the infusion product and boosted the antitumor immune response of bystander T cells, markedly improving the cytotoxicity of CAR19-T cells to lymphoma cells in vitro and in vivo. In addition, BV28-OKT3 elicited the cytotoxicity of donor-derived T cells toward lymphoma cells in vitro, which depended on the presence of tumor cells. Therefore, our findings provide a new clinical treatment strategy for recurrent and refractory B-cell lymphoma by combining CD79b/CD3 BsAb with CAR19-T cells.