Potent Anti-SARS-CoV-2 Activity by the Natural Product Gallinamide A and Analogues via Inhibition of Cathepsin L

Abstract

Cathepsin L is a key host cysteine protease utilized by coronaviruses for cell entry and is a promising drug target for novel antivirals against SARS-CoV-2. The marine natural product gallinamide A and several synthetic analogues were identified as potent inhibitors of cathepsin L with IC50 values in the picomolar range. Lead molecules possessed selectivity over other cathepsins and alternative host proteases involved in viral entry. Gallinamide A directly interacted with cathepsin L in cells and, together with two lead analogues, potently inhibited SARS-CoV-2 infection in vitro, with EC50 values in the nanomolar range. Reduced antiviral activity was observed in cells overexpressing transmembrane protease, serine 2 (TMPRSS2); however, a synergistic improvement in antiviral activity was achieved when combined with a TMPRSS2 inhibitor. These data highlight the potential of cathepsin L as a COVID-19 drug target as well as the likely need to inhibit multiple routes of viral entry to achieve efficacy.

Intramolecular interactions enhance the potency of gallinamide A analogs againstTrypanosoma cruzi

“…Introduction of biaryl-substituted MMP moieties at the C-terminus was explored by evaluating analogs 24-33 (Table 3). These compounds possessed either 4-(N-Me)piperidine or N,N-Me2-L-Val at the pseudo-N-terminus and CH2CH2-Ph at the P1 site 24,27 . All but one of the analogs of this series exhibited more potent activity against cruzain compared to gallinamide A.…”

“…P. falciparum falcipain enzymes are cathepsin L-like proteases and therefore additional studies showed that gallinamide A is also a potent and highly selective inhibitor of human cathepsin L 22 . The unique linear lipopeptide structure, and potential applicability to proteases of medical relevance, provoked interest in establishing chemical syntheses of gallinamide A and structural analogs 20,[23][24][25][26] . Indeed, gallinamide A has become an attractive starting point for developing selective inhibitors targeting human cathepsin L and other Clan CA cysteine proteases in human pathogens 21,23,24,27 .…”

“…The unique linear lipopeptide structure, and potential applicability to proteases of medical relevance, provoked interest in establishing chemical syntheses of gallinamide A and structural analogs 20,[23][24][25][26] . Indeed, gallinamide A has become an attractive starting point for developing selective inhibitors targeting human cathepsin L and other Clan CA cysteine proteases in human pathogens 21,23,24,27 . Based on comparison of the protein sequence alignment and substrate specificity, cathepsin L is similar to cysteine proteases from unicellular parasites that are responsible for neglected tropical diseases, such as falcipains from P. falciparum and cruzain from T. cruzi [28][29][30] .…”

“…Previously, fifteen gallinamide A analogs were synthesized and tested against cruzain and human cathepsin L 23 , while thirty-five additional analogs were synthesized and tested against falcipain-2 and -3 and P. falciparum. 21,27 Recently, both sets of analogs were evaluated against SARS-CoV-2 and analogs 19 and 23 demonstrated efficacy against viral infection in VeroE6 cells by inhibiting host cathepsin L in the picomolar range 24 . Analog numbering in this work is according to Ashhurst et al 24 .…”

“…21,27 Recently, both sets of analogs were evaluated against SARS-CoV-2 and analogs 19 and 23 demonstrated efficacy against viral infection in VeroE6 cells by inhibiting host cathepsin L in the picomolar range 24 . Analog numbering in this work is according to Ashhurst et al 24 . The gallinamide A analogs that exhibited activity against human cathepsin L also showed potent inhibition of cruzain and intracellular T. cruzi amastigotes, making the gallinamide scaffold a promising lead for anti-Chagas drug development 23 .…”