Potent Inhibition of Human Betacoronaviruses by a Short Double-Stapled Peptide Mimicking the HR2 Core Region in Viral Spike Protein

A small hexameric coiled-coil fusion complex formed by the interaction between α-helical motif of heptad repeat 2 (HR2_core) and HR1 core site (HR1_core) in human betacoronavirus spike protein plays a crucial role in facilitating membrane fusion. Formation of the six-helix bundle involves the evolutionary conservation of key residues in the HR1_core region. Therefore, to recapitulate the native conformation of the HR2_core peptide α-helix and the HR1_core site conserved residues, we employed hydrocarbon double-stapling. The resulting all-hydrocarbon stapled peptide M2PA shows highly potent and broad-spectrum antiviral activity against SARS-CoV-2 and its emerging variants, as well as other betacoronaviruses tested. Also, M2PA is effective against authentic SARS-CoV-2 infection in vivo, and it possesses outstanding pharmacokinetic properties. This represents the first successful minimization of a pan-coronavirus inhibitor to an HR2_core-based α-helical peptide, and as such, M2PA peptide stands as a promising candidate for drug development to combat coronavirus pandemics.