Abstract: The present disclosure provides heterodimeric antibodies that bind to two different target antigens at the same time. In one embodiment, the heterodimeric antibodies are bispecific antibodies. In one embodiment, the heterodimeric antibodies comprise three polypeptides including: a first polypeptide comprising an scFv-Fc fusion polypeptide; a second polypeptide comprising an immunoglobulin heavy chain; and a third polypeptide comprising an immunoglobulin light chain. In one embodiment, the first polypeptide includes one or more point mutations that confer increased thermal-stability to the first polypeptide.

Abstract: The present disclosure provides several embodiments of multi-specific antigen binding protein complexes. In some embodiments, the multi-specific antigen binding protein complex is composed of either two or three polypeptide chains that assemble with each other to form het-erodimeric complexes comprising two different Fab regions each capable of binding two different epitopes and comprising an Fc region which is capable of exhibiting Fc effector function, thus having a relatively simple structure compared to certain other multi-specific antibodies. In one embodiment, the multi-specific antigen binding protein complex is activatable as one of the polypeptide chains that compose the protein complex carries a cleavable linker.