Neutralizing multivalent antibodies against coronaviruses

The COVID-19 pandemic, induced by the emergent SARS-CoV-2 coronavirus (CoV), creates a global health emergency. Beyond health impacts, the pandemic has severe worldwide economic repercussions. As neither vaccines nor therapies are yet available to fight SARS-CoV-2 (and any other CoV)-induced diseases, the development of next-generation therapeutics is of paramount importance.The SARS-CoV-2 cell-entry process is mediated by the trimeric Spike (S) glycoprotein, which also represents a major viral antigen naturally targeted by the immune system. In this proposal, we propose to develop neutralizing multivalent single-chain antibodies (nmAb) to efficiently block viral cell-entry. Beyond potential therapeutic benefits, the initial asymptomatic phase induced by the virus may offer an attractive window of opportunity to establish post-exposure prophylaxis and prevention of rapid human-to-human transmissions. Engineering of nmAbs will be performed in two main steps: (i) selection of neutralizing synthetic single-domain antibodies (sybodies) targeting the receptor binding (S1) and fusion machinery (S2) functional domains of S-trimers, and (ii) linking of sybodies together with or without grafting to a human immunoglobulin Fc-region. Cell entry inhibition by the sybodies and derived antibody-like formats will be investigated in cell-based fusion assays as well as neutralization assays using pseudo-typed VSVs and recombinant-live viruses. We envisage developing nmAbs towards two different formulations: (i) up to three fused sybodies (triSy), devoid of an added Fc-region, for nebulization (inhaled mainly as prophylaxis); and (ii) nmAbs grafted onto engineered human Fc-region for injection as either a preventive measure or treatment of further-progressed disease. In our judgement, nmAbs exhibit the following clinical advantages. Firstly, they may outcompete conventional antibody potency, because they bind to multiple epitopes of the Spike simultaneously. Secondly, multivalent binding of nmAbs may mitigate the rapid emergence of drug-resistant viral variants. Thirdly, treatment with nmAbs may reduce antibody-dependent enhanced (ADE) illness, since Fc-mediated effector functions can be rationally attenuated. In conclusion, we are confident that the design of next-generation neutralizing multivalent single-chain antibodies may represent an essential first line of defense against this and future emerging coronavirus epidemics. Keywords Multivalent antibody engineering; Neutralizing sybodies; Spike protein; Coronavirus Hauptdisziplin Experimentelle Mikrobiologie