Abstract - Anthony Fehr

The Discovery of Novel SARS-CoV-2 Macrodomain Inhibitors

The emergence of several zoonotic viruses in the last twenty years, especially the pandemic outbreak of SARS-CoV-2, has exposed a dearth of antiviral drug therapies for viruses with pandemic potential.  Developing a diverse drug portfolio will be critical to rapidly respond to novel coronaviruses (CoVs) and other viruses with pandemic potential.  Here we focus on the SARS-CoV-2 conserved macrodomain (Mac1), a small domain of non-structural protein 3 (nsp3).  Mac1 is an ADP-ribosylhydrolase that cleaves mono-ADP-ribose (MAR) from target proteins, protects the virus from the anti-viral effects of host ADP-ribosyltransferases, and is critical for the replication and pathogenesis of CoVs.  In this study, a luminescent-based high-throughput assay was used to screen ~38,000 small molecules for those that could inhibit Mac1-ADP-ribose binding.  We identified 5 compounds amongst 3 chemotypes that inhibit SARS-CoV-2 Mac1-ADP-ribose binding in multiple assays with IC₅₀ values less than 100 𝜇M, inhibit ADP-ribosylhydrolase activity, and have evidence of direct Mac1 binding. Furthermore, structure-activity study identified 2 additional compounds that hit the same benchmarks, including compound 15c, which had low micromolar potency and bound to Mac1 as well as its natural substrate, ADP-ribose.  These chemotypes are strong candidates for further derivatization into highly effective Mac1 inhibitors.