Target cell killing effects of CD20 targeting chimeric antigen receptor T cells derived from the type II anti-CD20 antibody.

e14548Background: Chimeric Antigen Receptor T cells (CAR-Ts) targeting CD19 have shown very promising clinical outcomes in treatment of B-cell linage hematological malignancies. However, many patients with relapsed diseases were found to have down-regulated/loss of CD19 surface expression after CD19 CAR-T therapy. To solve this issue of CD19 single-targeting escape, we explored the application of another B-cell antigen, CD20, for targeted CAR-T therapy. Methods: We constructed four CD20 targeting CARs (all with 4-1BB co-stimulatory signaling) base on single-chain variable fragments (scFV) derived from four well-studied CD20 specific antibodies: Leu16, Rituximab, Obinutuzumab, and Ofatumumab. Leu16, Rituximab, and Obinutuzumab belong to the type I anti-CD20 antibody family and appear to bind to different epitopes located on the large loop of CD20, whereas Ofatumumab is the type II anti-CD20 antibody which has been shown to interact with the hydrophobic residues on the small loop surrounding a deep binding ...