Dual-target Bridging ELISA for Bispecific Antibodies

Bispecific antibodies (BsAbs) are typically monoclonal antibody (mAb)-derived molecular entities engineered to bind to two distinct targets, including two antigens or two epitopes on the same antigen. When compared to parental monoclonal antibodies or combinational therapies, the generated BsAbs have the ability to bridge the two targets and thus may offer additional clinical benefits. Characterizing BsAbs' ability to bind to both targets simultaneously is critical for their biotherapeutic development. A range of bi-functional quantitative bridging assays to enable targetspecific capture and detection of binding properties include enzyme-linked immunosorbent assay (ELISA), surface plasmon resonance (SPR), and cell-based flow cytometry. Developing suitable and robust cell-based bioassays is more challenging than non-cell-based binding assays because cell-based assays with complex matrices can be inherently variable and often lack precision. Compared to SPR, ELISA has a rapid setup and readily available method, being widely and extensively applied in almost every laboratory. Here, we describe a dual-target bridging ELISA assay that characterizes the ability of a HER2(human epidermal growth factor receptor 2)/PDL1(programmed cell death ligand 1) BsAb in binding to both HER2 and PD-L1 simultaneously, a prerequisite for its envisioned mode of action.