Antiviral Res

. 2023 Mar 2;105576.
doi: 10.1016/j.antiviral.2023.105576. Online ahead of print.
Novel bispecific human antibody platform specifically targeting a fully open spike conformation potently neutralizes multiple SARS-CoV-2 variants

Ji Woong Kim 1 , Kyun Heo 2 , Hyun Jung Kim 3 , Youngki Yoo 4 , Hyun-Soo Cho 4 , Hui Jeong Jang 5 , Ho-Young Lee 5 , In Young Ko 6 , Ju Rang Woo 6 , Yea Bin Cho 1 , Ji Hyun Lee 3 , Ha Rim Yang 3 , Ha Gyeong Shin 3 , Hye Lim Choi 3 , Kyusang Hwang 3 , Sokho Kim 7 , Hanseong Kim 8 , Kwangrok Chun 9 , Sukmook Lee 10



Rapid emergence of new variants of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has prompted an urgent need for the development of broadly applicable and potently neutralizing antibody platform against the SARS-CoV-2, which can be used for combatting the coronavirus disease 2019 (COVID-19). In this study, based on a noncompeting pair of phage display-derived human monoclonal antibodies (mAbs) specific to the receptor-binding domain (RBD) of SARS-CoV-2 isolated from human synthetic antibody library, we generated K202.B, a novel engineered bispecific antibody with an immunoglobulin G4-single-chain variable fragment design, with sub- or low nanomolar antigen-binding avidity. Compared with the parental mAbs or mAb cocktail, the K202.B antibody showed superior neutralizing potential against a variety of SARS-CoV-2 variants in vitro. Furthermore, structural analysis of bispecific antibody-antigen complexes using cryo-electron microscopy revealed the mode of action of K202.B complexed with a fully open three-RBD-up conformation of SARS-CoV-2 trimeric spike proteins by simultaneously interconnecting two independent epitopes of the SARS-CoV-2 RBD via inter-protomer interactions. Intravenous monotherapy using K202.B exhibited potent neutralizing activity in SARS-CoV-2 wild-type- and B.1.617.2 variant-infected mouse models, without significant toxicity in vivo. The results indicate that this novel approach of development of immunoglobulin G4-based bispecific antibody from an established human recombinant antibody library is likely to be an effective strategy for the rapid development of bispecific antibodies, and timely management against fast-evolving SARS-CoV-2 variants.

Keywords: Bispecific antibody; Cryo-EM; Immunoglobulin G4; Phage display; SARS-CoV-2 variants; Structural analysis.