An antibody panel that broadly neutralizes currently circulating Omicron variants was obtained by in vitro affinity maturation using phage display. Starting from a single parent clone, antibody engineering was performed in iterative stages in real time as variants emerged using a proprietary technology called STage-Enhanced Maturation (STEM). Humanized from a rabbit antibody, the parent clone showed undetectable neutralization of later Omicron variants, while an early stage IgG possessing only an engineered light chain potently neutralizes some BA.2 but not BA.4/BA.5 lineage variants. However, the final heavy and light chain engineered mAbs show potent neutralization of XBB.1.5 and BQ.1.1 by surrogate virus neutralization test, and biolayer interferometry shows pM K D affinity for both variants. Our work not only details novel therapeutic candidates but also validates a unique general strategy to create broadly neutralizing mAbs to current and future SARS-CoV-2 variants.

SARS-CoV-2 Omicron variant XBB.1.5 has shown extraordinary immune escape even for fully vaccinated individuals. There are currently no approved antibodies that neutralize this variant, and continued emergence of new variants puts immunocompromised and elderly patients at high risk. Rapid and cost-effective development of neutralizing antibodies is urgently needed. Starting with a single parent clone that neutralized the Wuhan-Hu-1 strain, antibody engineering was performed in iterative stages in real time as variants emerged using a proprietary technology called STage-Enhanced Maturation. An antibody panel that broadly neutralizes currently circulating Omicron variants was obtained by in vitro affinity maturation using phage display. The engineered antibodies show potent neutralization of BQ.1.1, XBB.1.16, and XBB.1.5 by surrogate virus neutralization test and pM KD affinity for all variants. Our work not only details novel therapeutic candidates but also validates a unique general strategy to create broadly neutralizing antibodies to current and future SARS-CoV-2 variants.