Structure-Based Optimization of ML300-Derived, Noncovalent Inhibitors Targeting the Severe Acute Respiratory Syndrome Coronavirus 3CL Protease (SARS-CoV-2 3CL<sup>pro</sup>).
Han SH, Goins CM, Arya T, Shin WJ, Maw J, Hooper A, Sonawane DP, Porter MR, Bannister BE, Crouch RD, Lindsey AA, Lakatos G, Martinez SR, Alvarado J, Akers WS, Wang NS, Jung JU, Macdonald JD, Stauffer SR.
Starting from the MLPCN probe compound ML300, a structure-based optimization campaign was initiated against the recent severe acute respiratory syndrome coronavirus (SARS-CoV-2) main protease (3CL<sup>pro</sup>). X-ray structures of SARS-CoV-1 and SARS-CoV-2 3CL<sup>pro</sup> enzymes in complex with multiple ML300-based inhibitors, including the original probe ML300, were obtained and proved instrumental in guiding chemistry toward probe compound <b>41</b> (CCF0058981). The disclosed inhibitors utilize a noncovalent mode of action and complex in a noncanonical binding mode not observed by peptidic 3CL<sup>pro</sup> inhibitors. <i>In vitro</i> DMPK profiling highlights key areas where further optimization in the series is required to obtain useful <i>in vivo</i> probes. Antiviral activity was established using a SARS-CoV-2-infected Vero E6 cell viability assay and a plaque formation assay. Compound <b>41</b> demonstrates nanomolar activity in these respective assays, comparable in potency to remdesivir. These findings have implications for antiviral development to combat current and future SARS-like zoonotic coronavirus outbreaks.