Constant domain-exchanged Fab enables specific light chain pairing in heterodimeric bispecific SEED-antibodies

IgG-like bispecific antibody platforms with built-in purification-facilitating elements

Assembly of IgG-like asymmetric bispecific antibodies (bsAbs) requires heavy chain heterodimerization and cognate heavy-light chain pairings. Multiple strategies have been developed to solve these chain association issues. While these strategies greatly promote correct chain pairing, they normally cannot prevent low amount of chain mispaired byproducts from being generated. Besides, byproducts can also be generated as a result of discordant chain expression. The existence of various byproducts poses considerable challenges to downstream processing during the production of recombinant IgG-like bsAbs. In many cases, yield is greatly compromised for purity improvement. This mini review introduces eight IgG-like bsAb platforms, which share a common feature: they all contain built-in purification-facilitating elements in addition to chain pairing control designs. These platforms, by simultaneously providing solutions to the two issues associated with bsAb production (i.e., correct chain pairing and efficient purification), improve both efficiency and robustness of bsAb production.

Bispecific Antibodies: From Research to Clinical Application

Bispecific antibodies (BsAbs) are antibodies with two binding sites directed at two different antigens or two different epitopes on the same antigen. The clinical therapeutic effects of BsAbs are superior to those of monoclonal antibodies (MoAbs), with broad applications for tumor immunotherapy as well as for the treatment of other diseases. Recently, with progress in antibody or protein engineering and recombinant DNA technology, various platforms for generating different types of BsAbs based on novel strategies, for various uses, have been established. More than 30 mature commercial technology platforms have been used to create and develop BsAbs based on the heterologous recombination of heavy chains and matching of light chains. The detailed mechanisms of clinical/therapeutic action have been demonstrated with these different types of BsAbs. Three kinds of BsAbs have received market approval, and more than 110 types of BsAbs are at various stages of clinical trials. In this paper, we elaborate on the classic platforms, mechanisms, and applications of BsAbs. We hope that this review can stimulate new ideas for the development of BsAbs and improve current clinical strategies.

Potent Cytolytic Activity and Specific IL15 Delivery in a Second-Generation Trispecific Killer Engager

Natural killer (NK) cells are potent immune modulators that can quickly lyse tumor cells and elicit inflammatory responses. These characteristics make them ideal candidates for immunotherapy. However, unlike T cells, NK cells do not possess clonotypic receptors capable of specific antigen recognition and cannot expand via activating receptor signals alone. To enable NK cells with these capabilities, we created and have previously described a tri-specific killer engager (TriKE) platform capable of inducing antigen specificity and cytokine-mediated NK-cell expansion. TriKE molecules have three arms: (i) a single-chain variable fragment (scFv) against the activating receptor CD16 on NK cells to trigger NK-cell activation, (ii) an scFv against a tumor-associated antigen (CD33 here) to induce specific tumor target recognition, and (iii) an IL15 moiety to trigger NK-cell expansion and priming. Here, we demonstrate that by modifying the anti-CD16 scFv with a humanized single-domain antibody against CD16, we improved TriKE functionality. A CD33-targeting second-generation TriKE induced stronger and more specific NK-cell proliferation without T-cell stimulation, enhanced in vitro NK-cell activation and killing of CD33-expressing targets, and improved tumor control in preclinical mouse models. Given these improved functional characteristics, we propose rapid translation of second-generation TriKEs into the clinic.