Bispecific antibodies targeting distinct regions of the spike protein potently neutralize SARS-CoV-2 variants of concern

Abstract

Description Bispecific antibodies targeting multiple regions of the SARS-CoV-2 spike protein comparably neutralize variants of concern and wild-type virus. A bispecific approach to COVID-19 Monoclonal antibodies (mAbs) have become an essential component of coronavirus disease 2019 (COVID-19) treatment. Most mAbs are administered as a cocktail of multiple antibodies that target different regions of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) virion. Here, Cho et al. further improved upon this strategy by identifying mAbs that, when combined as bispecific antibodies, neutralized SARS-CoV-2 better than cocktails of the parental mAbs. These bispecific antibodies bound to distinct regions of the SARS-CoV-2 spike protein, neutralized variants of concern, including the Delta variant, and conferred protection when administered to hamsters before SARS-CoV-2 infection. Together, these findings suggest that bispecific antibodies merit further consideration as variant-resistant SARS-CoV-2 therapeutics. The emergence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variants of concern threatens the efficacy of existing vaccines and therapeutic antibodies and underscores the need for additional 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 collected from patients with coronavirus disease 2019. The three most potent antibodies targeted distinct regions of the receptor binding domain (RBD), and all three neutralized the SARS-CoV-2 Alpha and Beta variants. 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 angiotensin-converting enzyme 2 receptor, and has limited contact with key variant residues K417, E484, and N501. We designed bispecific antibodies by combining nonoverlapping specificities and identified five bispecific antibodies that inhibit SARS-CoV-2 infection at concentrations of less than 1 ng/ml. Through a distinct mode of action, three bispecific antibodies cross-linked adjacent spike proteins using dual N-terminal domain–RBD specificities. One bispecific antibody was greater than 100-fold more potent than a cocktail of its parent monoclonals in vitro and prevented clinical disease in a hamster model at a dose of 2.5 mg/kg. Two bispecific antibodies in our panel comparably neutralized the Alpha, Beta, Gamma, and Delta variants and wild-type virus. Furthermore, a bispecific antibody that neutralized the Beta variant protected hamsters against SARS-CoV-2 expressing the E484K mutation. Thus, bispecific antibodies represent a promising next-generation countermeasure against SARS-CoV-2 variants of concern.