CD19/79b Bi-specific CAR-T Cells Targeting B Cell Malignancies

Patients with refractory and/or recurrent B cell malignancies have poor prognosis despite complex multimodal therapy. Despite impressive progress, more than 50% of patients treated with CD19-targeting chimeric antigen receptor T cells (CAR19) experience progressive disease. Further, more than 40% patients with progressive large B cell lymphoma (LBCL) experienced reduced or lost expression of CD19 on the tumor cells after CAR19 treatment; low surface CD19 density before treatment was associated with progressive disease. Therefore, novel curative approaches are needed. The investigation attempts to use genetically modified T cells to express a 4th generation lentiviral anti-CD19/79b bi-specific CAR (bi-4SCAR-CD19/79b). The CAR molecules enable the T cells to recognize and kill tumor cells through the recognition of a surface antigen, CD19 or CD79b, which is expressed at high levels on tumor cells but not at significant levels on normal tissues.

CD79b is a B cell surface antigen, which is a component of B cell receptor. CD79b is up-regulated in more than 90% of B-cell lymphomas. Recent studies have shown that CD79b CAR-T cells have potential in targeting B-cell lymphomas. In addition, several immunotherapy drugs based on targeting CD79b have been reported worldwide. The CD79b specific CAR-T cells with binding moiety of CD79b specific scFv exhibited a high affinity and antitumor effect against CD79b+ tumor cells.

A potential strategy to prevent relapse due to antigen escape is to infuse T-cells capable of recognizing multiple antigens. To overcome tumor escape of single target antigen and enhance in vivo CAR-T efficacy, a novel bi-specific CD19/79b CAR-T therapy regimen is developed to include booster and consolidation CAR-T applications to target highly-refractory B cell cancer. The aim is to evaluate safety and long term efficacy of the bi-CAR-T therapy strategy in CD19 and/or CD79b positive cancer patients.