Ultrapotent bispecific antibodies neutralize emerging SARS-CoV-2 variants

Cho, Hyeseon; Gonzales-Wartz, Kristina Kay; Huang, Deli; Yuan, Meng; Peterson, Mary; Liang, Janie; Beutler, Nathan; Torres, Jonathan L.; Cong, Yu; Postnikova, Elena; Bangaru, Sandhya; Talana, Chloe Adrienna; Shi, Wei; Yang, Eun Sung; Zhang, Yi; Leung, Kwanyee; Wang, Lingshu; Peng, Linghang; Skinner, Jeff; Li, Shanping; Wu, Nicholas C.; Liu, Hejun; Dacon, Cherrelle; Moyer, Thomas; Cohen, Melanie; Zhao, Ming; Lee, F. Eun-Hyung; Weinberg, Rona S.; Douagi, Iyadh; Gross, Robin; Schmaljohn, Connie; Pegu, Amarendra; Mascola, John R.; Holbrook, Michael; Nemazee, David; Rogers, Thomas F.; Ward, Andrew B.; Wilson, Ian A.; Crompton, Peter D.; Tan, Joshua

The emergence of SARS-CoV-2 variants that threaten the efficacy of existing vaccines and therapeutic antibodies underscores the urgent need for new antibody-based tools that potently neutralize variants by targeting multiple sites of the spike protein. We isolated 216 monoclonal antibodies targeting SARS-CoV-2 from plasmablasts and memory B cells of COVID-19 patients. The three most potent antibodies targeted distinct regions of the RBD, and all three neutralized the SARS-CoV-2 variants B.1.1.7 and B.1.351. The crystal structure of the most potent antibody, CV503, revealed that it binds to the ridge region of SARS-CoV-2 RBD, competes with the ACE2 receptor, and has limited contact with key variant residues K417, E484 and N501. We designed bispecific antibodies by combining non-overlapping specificities and identified five ultrapotent bispecific antibodies that inhibit authentic SARS-CoV-2 infection at concentrations of <1 ng/mL. Through a novel mode of action three bispecific antibodies cross-linked adjacent spike proteins using dual NTD/RBD specificities. One bispecific antibody was >100-fold more potent than a cocktail of its parent monoclonals in vitro and prevented clinical disease in a hamster model at a 2.5 mg/kg dose. Notably, six of nine bispecific antibodies neutralized B.1.1.7, B.1.351 and the wild-type virus with comparable potency, despite partial or complete loss of activity of at least one parent monoclonal antibody against B.1.351. Furthermore, a bispecific antibody that neutralized B.1.351 protected against SARS-CoV-2 expressing the crucial E484K mutation in the hamster model. Thus, bispecific antibodies represent a promising next-generation countermeasure against SARS-CoV-2 variants of concern.