Macrocyclic Azapeptide Nitriles: Structure-Based Discovery of Potent SARS-CoV-2 Main Protease Inhibitors as Antiviral Drugs
Julian Breidenbach, Rabea Voget, Yaoyao Si, Alexandra Hingst, Tobias Claff, Katharina Sylvester, Valentina Wolf, Vesa Krasniqi, Abibe Useini, Norbert Sträter, Yukino Ogura, Atsushi Kawaguchi, Christa E. Müller, Michael Gütschow
Abstract
Given the crucial role of the main protease (M pro ) in the replication cycle of SARS-CoV-2, this viral cysteine protease constitutes a high-profile drug target. We investigated peptidomimetic azapeptide nitriles as auspicious, irreversibly acting inhibitors of M pro . Our systematic approach combined an M pro active-site scanning by combinatorially assembled azanitriles with structure-based design. Encouraged by the bioactive conformation of open-chain inhibitors, we conceptualized the novel chemotype of macrocyclic azanitriles whose binding mode was elucidated by cocrystallization. This strategy provided a favorable entropic contribution to target binding and resulted in the development of the extraordinarily potent M pro inhibitor 84 with an IC 50 value of 3.23 nM and a second-order rate constant of inactivation, k inac / K i, of 448,000 M –1 s –1 . The open-chain M pro inhibitor 58, along with the macrocyclic compounds 83 and 84, a broad-spectrum anticoronaviral agent, demonstrated the highest antiviral activity with EC 50 values in the single-digit micromolar range. Our findings are expected to promote the future development of peptidomimetic M pro inhibitors as anti-SARS-CoV-2 agents.