DESIGN OF A CHIMERIC ACE-2/Fc-SILENT FUSION PROTEIN WITH ULTRAHIGH AFFINITY AND NEUTRALIZING CAPACITY FOR SARS-CoV-2 VARIANTS

As the coronavirus SARS-CoV-2 continues to mutate into Variants of Concern (VOC), there is a growing and urgent need to develop effective antivirals to combat the newly emerged infectious disease COVID-19. Recent data indicate that monoclonal antibodies developed early in the pandemic are no longer capable of effectively neutralizing currently active VOCs. This report describes the design of a class of variant-agnostic chimeric molecules consisting of an Angiotensin Converting Enzyme-2 (ACE-2) domain mutated to retain ultrahigh affinity binding to a wide variety of SARS-CoV-2 variants, coupled to an Fc-silent immunoglobulin domain that eliminates antibody-dependent enhancement (ADE) and simultaneously extends biological half-life compared to existing mABs. Molecular modeling revealed that ACE-2 mutations L27, V34 and E90 resulted in ultrahigh affinity binding of the LVE-ACE-2 domain to the widest variety of VOCs, with KDs of 93 pM, 507 pM and 73 pM for binding to the Alpha B1.1.7, Delta B.1.617.2 and Omicron B.1.1.529 variants, and notably, 78fM affinity to the Omicron BA.2 variant, respectively. Surrogate viral neutralization assays (sVNT) revealed titers of[≥] 4.9ng/ml, for neutralization of recombinant viral proteins corresponding to the Alpha, Delta and Omicron variants. The values above were obtained with LVE-ACE-2/mAB chimeras containing the Y-T-E sequence that enhances binding to the FcRn receptor, which in turn is expected to extend biological half-life 3-4-fold. It is proposed that this new class of chimeric ACE-2/mABs will constitute variant-agnostic and cost-effective prophylactics against SARS-CoV-2, particularly when administered by nasal delivery systems.