Multi-specific DARPin(R) therapeutics demonstrate very high potency against mutated SARS-CoV-2 variants in vitro

The SARS-CoV-2 virus responsible for the COVID-19 pandemic has so far infected more than 100 million people globally, and continues to undergo genomic evolution. Emerging SARS-CoV-2 variants show increased infectivity and may lead to resistance against immune responses of previously immunized individuals or existing therapeutics, especially antibody-based therapies. Several monoclonal antibody therapeutics authorized for emergency use or in development start to lose potency against various SARS-CoV-2 variants. Cocktails of two different monoclonal antibodies constitute a promising approach to protect against such variants as long as both antibodies are potent, but come with increased development complexity and therefore cost. As an alternative, we developed two multi-specific DARPin(R) therapeutics, each combining three independent DARPin(R) domains binding the SARS-CoV-2 spike protein in one molecule, to potently neutralize the virus and overcome virus escape. Here, we show in a panel of in vitro studies that both multi-specific DARPin(R) therapeutics, ensovibep (MP0420) and MP0423, are highly potent against the new circulating SARS-CoV-2 variants B.1.1.7 (UK variant) and B.1.351 (South African variant) and the most frequent emerging mutations in the spike protein. Additionally, viral passaging experiments show potent protection by ensovibep and MP0423 against development of escape mutations. Furthermore, we demonstrate that the cooperative binding of the individual modules in a multi-specific DARPin(R) antiviral is key for potent virus inhibition and protection from escape variants. These results, combined with the relatively small size and high production yields of DARPin(R) molecules, suggests ensovibep and MP0423 as superior alternatives to monoclonal antibody cocktails for global supply and demonstrate the strength of the DARPin(R) platform for achieving potent and lasting virus inhibition for SARS-CoV-2 and possibly other viruses.