EFab domain substitution as a solution to the light-chain pairing problem of bispecific antibodies.

Bispecific antibody therapeutics can expand the functionality of a conventional monoclonal antibody drug because they can bind multiple antigens. However, their great potential is counterbalanced by the challenges faced in their production. The classic asymmetric bispecific containing an Fc requires the expression of four unique chains - two light chains and two heavy chains; each light chain must pair with its correct heavy chain, which then must heterodimerize to form the full bispecific.