Antiviral Activity against SARS-CoV-2 of Conformationally Constrained Helical Peptides Derived from Angiotensin-Converting Enzyme 2

Abstract

Despite the availability of vaccines, COVID-19 continues to be aggressive, especially in immunocompromised individuals. Therefore, the development of a specific therapeutic agent with antiviral activity against SARS-CoV-2 is necessary. The infection pathway starts when the <i>receptor binding domain</i> of the viral spike protein interacts with the <i>angiotensin converting enzyme 2</i> (ACE2), which acts as a host receptor for the RBD expressed on the host cell surface. In this scenario, ACE2 analogs binding to the RBD and preventing the cell entry can be promising antiviral agents. Most of the ACE2 residues involved in the interaction belong to the α1 helix, more specifically to the minimal fragment ACE2(24-42). In order to increase the stability of the secondary structure and thus antiviral activity, we designed different triazole-stapled analogs, changing the position and the number of bridges. The peptide called <b>P3</b>, which has the triazole-containing bridge in the positions 36-40, showed promising antiviral activity at micromolar concentrations assessed by plaque reduction assay. On the other hand, the double-stapled peptide <b>P4</b> lost the activity, showing that excessive rigidity disfavors the interaction with the RBD.