Peptidomimetic\nAnalogues Act as Effective Inhibitors\nagainst SARS-CoV‑2 by Blocking the Function of Cathepsin L

Cathepsin L (CatL) is a promising antiviral drug target\nof severe\nacute respiratory syndrome coronavirus 2 (SARS-CoV-2) as an important\nprotease for cleaving the SARS-CoV-2 spike protein and enhancing viral\nentry to cells. We identified a tripeptide aldehyde candidate, <b>D1–1</b>, which exhibited inhibitory effects against SARS-CoV-2\nin Vero E6 cells. The protease screening analysis and protein pull-down\nassays demonstrated the direct binding of <b>D1–1</b> to CatL. Guided by molecular docking, we synthesized 72 analogues.\nUpon analyzing the structure–activity relationships of these\ninhibitors, the <b>D6</b> series was developed. Among them, <b>D6–3</b> functioned as the most potent CatL inhibitor (IC<sub>50</sub> = 0.27 nM, EC<sub>50</sub> = 0.26 μM). <b>D6–3</b> effectively blocked the CatL function and substantially hindered\nthe entry of the SARS-CoV-2 pseudovirus to cells. Our work presented\nnovel compounds for targeting and inhibiting CatL, offering valuable\ninsights into the development of SARS-CoV-2 antivirals.