BC‐11 is a covalent TMPRSS2 fragment inhibitor that impedes SARS‐CoV‐2 host cell entry

Abstract

Host cell entry of severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2) is facilitated via priming of its spike glycoprotein by the human transmembrane protease serine 2 (TMPRSS2). Although camostat and nafamostat are two highly potent covalent TMPRSS2 inhibitors, they nevertheless did not hold promise in COVID‐19 clinical trials, presumably due to their short plasma half‐lives. Herein, we report an integrative chemogenomics approach based on computational modeling and in vitro enzymatic assays, for repurposing serine‐targeted covalent inhibitors. This led to the identification of BC‐11 as a covalent TMPRSS2 inhibitor displaying a unique selectivity profile for serine proteases, ascribable to its boronic acid warhead. BC‐11 showed modest inhibition of SARS‐CoV‐2 (omicron variant) spike pseudotyped particles in a cell‐based entry assay, and a combination of BC‐11 and AHN 1‐055 (a spike glycoprotein inhibitor) demonstrated better viral entry inhibition than either compound alone. Given its low molecular weight and good activity against TMPRSS2, BC‐11 qualifies as a good starting point for further structural optimizations.

In Silico and In Vitro Evaluation of Some Amidine Derivatives as Hit Compounds towards Development of Inhibitors against Coronavirus Diseases

“…This fragment of nafamostat establishes a network of favorable interactions that involve the hydrogen bond between its carbonyl and Gln438 and Gly439 residues in addition to hydrogen bonding interactions between the guanidine functionality with Asp435, Ser436, Gly464 and Gly472 residues. In fact, the presence of a guanidinium moiety in a structure of proposed inhibitor was found to be crucial to the binding with TMPRSS2 [ 17 , 65 ].…”

Structural understanding of SARS-CoV-2 virus entry to host cells

“…Although clinical trials of TMPRSS2 inhibitors nafamostat mesylate and camostat mesylate for COVID-19 treatment failed, drug identification by repurposing remains a promising approach. For example, the TMPRSS2 inhibitor BC-11, recently identified by this approach, has the potential to be further optimized for clinical trials to treat COVID-19 since it shows several advantages in terms of drug development due to its small molecular weight (Tsukagoshi, 2000;Moumbock et al, 2023). New approaches such as nanobodies and aptamers targeting RBD and preventing RBD-hACE2 interactions also provide new opportunities for COVID-19 treatments (Liu et al, 2021c;Sun et al, 2021;Xu et al, 2021;Yang et al, 2022a).…”

A Tale of Two Proteases: MPro and TMPRSS2 as Targets for COVID-19 Therapies

“…Most drugs targeting TMPRSS2 as antiviral COVID-19 agents are repurposed TMPRSS2 inhibitors that have already shown activity in other types of diseases. Thus, efficient inhibitors identified so far range from small organic molecules (i.e., camostat and nafamostat, Figure 9) [87,59] to proteins, such as aprotinin [62]. [55].…”

“…Most drugs targeting TMPRSS2 as antiviral COVID-19 agents are repurposed TMPRSS2 inhibitors that have already shown activity in other types of diseases. Thus, efficient inhibitors identified so far range from small organic molecules (i.e., camostat and nafamostat, Figure 9) [59,87] to proteins, such as aprotinin [62]. Camostat and nafamostat are 4-guanidinophenyl esters that act as covalent inhibitors undergoing trans-esterification in the TMPRSS2 active site, thus trapping the Ser441 involved in the catalytic triad (see mechanism of inhibition of camostat in Figure 10) [14].…”

“…It has reappeared again as a drug of intere because of its ability as a TMPRSS2 inhibitor and hence a potential COVID-19 therap [61]. Another interesting inhibitor of TMPRSS2 is the amidinium-containing small molecule BC-11, which was found by Günther's group (Figure 10) [59]. This compound contains an unusual boronic acid moiety as well as carbamidothioate and seems to covalently inhibit protease activity by trapping the catalytic serine residue as camostat and nafamostat.…”