A novel biparatopic hybrid antibody-ACE2 fusion that blocks SARS-CoV-2 infection: implications for therapy

Abstract

In the absence of a proven effective vaccine preventing infection by SARS-CoV-2, or a proven drug to treat COVID-19, the positive results of passive immune therapy using convalescent serum provide a strong lead. We have developed a new class of tetravalent, biparatopic therapy, 89C8-ACE2. It combines the specificity of a monoclonal antibody (89C8) that recognizes the relatively conserved N-terminal domain of the viral Spike (S) glycoprotein, and the ectodomain of ACE2, which binds to the receptor-binding domain of S. This molecule shows exceptional performance in vitro, inhibiting the interaction of recombinant S1 to ACE2 and transduction of ACE2-overexpressing cells by S-pseudotyped lentivirus with IC50s substantially below 100 pM, and with potency approximately 100-fold greater than ACE2-Fc itself. Moreover, 89C8-ACE2 was able to neutralize authentic viral infection in a standard 96-h co-incubation assay at low nanomolar concentrations, making this class of molecule a promising lead for therapeutic applications.

Keywords: Biparatopic; COVID-19; SARS-CoV-2; antibody-ACE2 fusion; neutralizing antibody.

Figure 1.

A schematic diagram showing the workflow of antibody discovery.

Figure 2.

2a) schematic illustration of the biparatopic 89C8-ACE2 antibody-fusion design; BLI binding kinetics of 89C8 (2b), ACE2-Fc (2 c) and 89C8-ACE2 (2d) binding to the spike protein S1 (monovalent K_D); 2e) 89C8-ACE2 binding to the spike protein in the avid format. In 2b-d, 2-fold dilutions of S1 protein, starting at 100 nM, were used. In 2e, dilution series of 89C8-ACE2 with a starting concentration of 20 nM, with 2-fold dilutions, were used.

Figure 3.

Blocking and neutralization experiments by 89C8, ACE2-Fc and 89 C8-ACE2 between 3a) Spike protein S1 (m-Fc format) with CHO cells overexpressing ACE2; 3b) pseudovirus with HEK293 cells overexpressing ACE2; 3 c) Live virus (Australia/Vic1/2020) plaque reduction neutralization test with Vero cells, VHH72-Fc was included as a positive control.