Functional NK engagers from OmniClic, a common light-chain platform producing fully human-sequence antibodies in a chicken host species

Next-generation antibodies include a growing number of bispecific and multispecific antibodies that are commonly used to redirect the immune system to fight cancer. Herein, we assessed the depth and breadth of epitope coverage as a proxy for functional diversity in human immune repertoires produced by two complementary <i>in vivo</i> platforms utilizing a common light chain, in a chicken (OmniClic^TM) or rat (OmniFlic®) host species. We adopted NKp46 as a model to target antigen due to its use in emerging natural killer (NK) immune engagers that are being explored clinically as potentially safer alternatives to traditional CD3-based T cell engagers. To probe the epitope diversity of our antibody repertoires, we performed a detailed high throughput epitope binning study using surface plasmon resonance and corroborated our binning assignments with epitope mapping data deduced from hydrogen deuterium exchange mass spectrometry. Our results revealed broad epitope coverage and nuanced diversity both within and across repertoires, with few epitopes shared, suggesting that the complementary use of OmniClic^TM and OmniFlic® produces more comprehensive coverage than either alone. Furthermore, our epitope binning assignments aligned with our complementarity-determining region-based sequence lineage assignments, enabling a direct comparison of sequence diversity across Clic and Flic repertoires despite their use of different scaffolds, a single functionally rearranged V(D)J scaffold versus multiple combinatorially assembled V(D)J scaffolds, respectively. The rich epitope diversity of both OmniClic^TM and OmniFlic® yielded multiple candidates for functional NK activators, as determined in an antibody-dependent cellular cytotoxicity assay, demonstrating their value as building blocks in constructing optimized immune engagers.