Potent in vitro anti-SARS-CoV-2 activity by gallinamide A and analogues via inhibition of cathepsin L

Ashhurst, Anneliese S.; Tang, Arthur H.; Fajtová, Pavla; Yoon, Michael; Aggarwal, Anupriya; Stoye, Alexander; Larance, Mark; Beretta, Laura; Drelich, Aleksandra; Skinner, Danielle; Li, Linfeng; Meek, Thomas D.; McKerrow, James H.; Hook, Vivian; Tseng, Chien-Te K.; Turville, Stuart; Gerwick, William H.; O’Donoghue, Anthony J.; Payne, Richard J.

The emergence of SARS-CoV-2 in late 2019, and the subsequent COVID-19 pandemic, has led to substantial mortality, together with mass global disruption. There is an urgent need for novel antiviral drugs for therapeutic or prophylactic application. Cathepsin L is a key host cysteine protease utilized by coronaviruses for cell entry and is recognized as a promising drug target. The marine natural product, gallinamide A and several synthetic analogues, were identified as potent inhibitors of cathepsin L activity with IC50 values in the picomolar range. Lead molecules possessed selectivity over cathepsin B and other related human cathepsin proteases and did not exhibit inhibitory activity against viral proteases Mpro and PLpro. We demonstrate that gallinamide A and two lead analogues potently inhibit SARS-CoV-2 infection in vitro, with EC50 values in the nanomolar range, thus further highlighting the potential of cathepsin L as a COVID-19 antiviral drug target.