Abstract
Broadly neutralizing antibodies are an important treatment for individuals with coronavirus disease 2019 (COVID-19) caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Antibody-based therapeutics are also essential for pandemic preparedness against future Sarbecovirus outbreaks. Camelid-derived single domain antibodies (VHHs) exhibit potent antimicrobial activity and are being developed as SARS-CoV-2–neutralizing antibody-like therapeutics. Here, we identified VHHs that neutralize both SARS-CoV-1 and SARS-CoV-2, including now circulating variants. We observed that the VHHs bound to a highly conserved epitope in the receptor binding domain of the viral spike protein that is difficult to access for human antibodies. Structure-guided molecular modeling, combined with rapid yeast-based prototyping, resulted in an affinity enhanced VHH-human immunoglobulin G1 Fc fusion molecule with subnanomolar neutralizing activity. This VHH-Fc fusion protein, produced in and purified from cultured Chinese hamster ovary cells, controlled SARS-CoV-2 replication in prophylactic and therapeutic settings in mice expressing human angiotensin converting enzyme 2 and in hamsters infected with SARS-CoV-2. These data led to affinity-enhanced selection of the VHH, XVR011, a stable anti–COVID-19 biologic that is now being evaluated in the clinic.
Highlights
Infection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) can lead to severe disease, characterized by dyspnea, hypoxemia, and acute respiratory distress, and can be fatal
Structure-guided molecular modeling, combined with rapid yeast-based prototyping, resulted in an affinity enhanced VHH-human IgG1 Fc fusion molecule with subnanomolar neutralizing activity. This VHH-Fc fusion protein, produced in and purified from cultured Chinese hamster ovary cells, controlled SARS-CoV-2 replication in prophylactic and therapeutic settings in mice expressing human angiotensin converting enzyme 2 (ACE2) and in hamsters infected with SARS-CoV-2
To obtain additional evidence of the in vivo protective potential of our broadly neutralizing VHH72-Fc prototype, we employed mice expressing human ACE2 driven by the keratin 18 promotor (K18-hACE2 transgenic mice), which are susceptible to SARS-CoV-1 and -2 infection [18, 19]
Summary
Infection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) can lead to severe disease, characterized by dyspnea, hypoxemia, and acute respiratory distress, and can be fatal. Since its first emergence in humans, SARS-CoV-2 variants with acquired mutations in the immunodominant receptor-binding motif (RBM) have emerged Some of these variants are of concern (VOCs) because they spread rapidly or evade host immunity. As a consequence, these VOCs display increased resistance to neutralization by convalescent plasma-derived monoclonal antibodies, including two of the three that have received emergency use approval in the USA [5, 12]. These VOCs display increased resistance to neutralization by convalescent plasma-derived monoclonal antibodies, including two of the three that have received emergency use approval in the USA [5, 12] This reinforces the need to develop neutralizing antibodies that bind to conserved regions of the SARS-CoV-2 spike protein
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