Cell-Based Assays to Optimize Bi-Specific Antibodies

Determining which fragment antigen-binding (Fab) interfaces to combine so that it will not affect the function or affinity of either arm is a significant challenge. Few cell-based assays exist that can quantitatively determine an appropriate combination of Fabs to generate a functional bi-specific antibody.

We have developed a simple assay that measures the ability of a bi-specific antibody to bring two receptors together on the surface of an intact cell. This assay enables rapid & quantitative differentiation between a bi-specific antibody’s ability to bind both receptors appropriately and bring them together. This assay has been used to identify appropriate Fab combinations and optimize the dual-binding of bi-specific antibodies so that only the ones with high affinity binding to both receptors are tested in your functional assay.

Dimerization Assay Principle


Technology Schematic for Bi-specific antibody principle

The dimerization assay format has been successfully used to quantitatively monitor and optimize the potency of bi-specific antibodies. The two target receptors are tagged with PK or EA and expressed in the same cell line. Upon binding the bi-specific antibody, the receptors are brought in close proximity, reconstituting an active β-galactosidase enzyme which hydrolyzes substrate to generate a chemiluminescent signal.