Novel Tri-Specific Immuno-Modulatory Antibody Combined with HDACi to Potentiate T Cell Activation and Anti-Tumor Efficacy

<b>Background:</b> Although blinatumomab, a bispecific T-cell engager, has exhibited promising clinical outcomes in the treatment of B-precursor acute lymphoblastic leukemia (B-ALL) and B cell non-Hodgkin's lymphoma (B-NHL), it still has some limitations due to CD19-negative relapse and an immunosuppressive phenotype. Epigenetic modulators have the potential to influence the tumor microenvironment (TME) and immune cycle in various ways. Combining multiple drugs is a trend in tumor treatment. <b>Methods:</b> In this article, we generated a novel tri‑specific antibody, called CiTE (CD3-BAFF-R-PD-L1), which is composed of a CD3 binding Fab frame, a BAFF-R binding scFv, and an additional scFv derived from PD‑L1. The cytotoxicity of T cells induced by CiTE (CD3-BAFF-R-PD-L1) was detected in combination with Chidamide. <b>Results:</b> The purified CiTE (CD3-BAFF-R-PD-L1) exhibited high binding capability for CD3-positive cells, BAFF-R-positive cells, and PD-L1-positive cells. Consequently, specific lysis towards BAFF-R-positive cell lines were induced by CiTE (CD3-BAFF-R-PD-L1) in the presence of T cells. We also confirmed that Chidamide could enhance T-cell mediated lysis by upregulating antigen strength on tumor cells and altering the TME by increasing the expression of T cell-attracting chemokines and costimulatory molecules. <b>Conclusions:</b> The novel tri-specific antibody combined with Chidamide holds promise as a safe and effective drug for the treatment of B-cell malignancies, due to its integration of three sections targeting different molecules into one compound.