Development of bispecific antibodies with enhanced neutralization activity against tested SARS-CoV-2 Omicron...

The COVID-19 pandemic, driven by the SARS-CoV-2 virus, has posed significant global health challenges, exacerbated by the emergence of the highly mutable Omicron variant. This study explores the potential of bispecific antibodies (bsAbs) in neutralizing this variant more effectively compared to traditional monoclonal antibodies (mAbs) and their combinations.

A comprehensive approach was utilized involving a fully human antibody phage-display library, Omni-Mab, to identify and enrich phage clones specific to SARS-CoV-2. Recombinant spike receptor-binding domain (RBD) proteins from the Omicron variant and other strains served as antigens during the biopanning process to ensure a broad screening. Post-enrichment, the binding affinity of the antibodies to the spike proteins of various strains was rigorously evaluated. Antibodies demonstrating strong binding efficacy were strategically combined and engineered into bsAbs. The neutralizing efficacy of these bsAbs was subsequently tested using various strains of the SARS-CoV-2 pseudo-viruses.

Selected parental mAbs showed kinetic profiles ranging from 5.71 x 10-¹⁰ to 2.53 x 10-⁴ M across the tested Omicron subvariants, and the lead bsAbs, particularly R3-1a-1/R4-1a-10 and R4-21/R4-1a-51, demonstrated enhanced binding activity and lower IC50 values than the controls and mAb cocktails.

The research unveiled two highly promising bsAbs, namely, R3-1a-1/R4-1a-10 scFv and R4-21/R4-1a-51 scFv. These bsAbs showed strong binding and neutralizing activity across the tested Omicron subvariants and retained activity against selected non-Omicron pseudovirus strains evaluated in this study.