Small-Molecule Inhibitors of the Coronavirus Spike: ACE2 Protein–Protein Interaction as Blockers of Viral Attachment and Entry for SARS-CoV-2

Abstract

Inhibitors of the protein–protein interaction (PPI) between the SARS-CoV-2 spike protein and human ACE2 (hACE2), which acts as a ligand–receptor pair that initiates the viral attachment and cellular entry of this coronavirus causing the ongoing COVID-19 pandemic, are of considerable interest as potential antiviral agents. While blockade of such PPIs with small molecules is more challenging than that with antibodies, small-molecule inhibitors (SMIs) might offer alternatives that are less strain- and mutation-sensitive, suitable for oral or inhaled administration, and more controllable/less immunogenic. Here, we report the identification of SMIs of this PPI by screening our compound library focused around the chemical space of organic dyes. Among promising candidates identified, several dyes (Congo red, direct violet 1, Evans blue) and novel druglike compounds (DRI-C23041, DRI-C91005) inhibited the interaction of hACE2 with the spike proteins of SARS-CoV-2 as well as SARS-CoV with low micromolar activity in our cell-free ELISA-type assays (IC 50 ’s of 0.2–3.0 μM), whereas control compounds, such as sunset yellow FCF, chloroquine, and suramin, showed no activity. Protein thermal shift assays indicated that the SMIs of interest identified here bind SARS-CoV-2-S and not hACE2. While dyes seemed to be promiscuous inhibitors, DRI-C23041 showed some selectivity and inhibited the entry of two different SARS-CoV-2-S expressing pseudoviruses into hACE2-expressing cells in a concentration-dependent manner with low micromolar IC 50 ’s (6–7 μM). This provides proof-of-principle evidence for the feasibility of small-molecule inhibition of PPIs critical for SARS-CoV-2 attachment/entry and serves as a first guide in the search for SMI-based alternative antiviral therapies for the prevention and treatment of diseases caused by coronaviruses in general and COVID-19 in particular.

In Silico Evaluation of Iranian Medicinal Plant Phytoconstituents as Inhibitors against Main Protease and the Receptor-Binding Domain of SARS-CoV-2

“…Therefore, if a small molecule can bind to RBD, it will hypothetically inhibit their viral infection of host cells. Several in vitro analyses have proven that RBD can be a target for viral entry inhibition [ 18 , 19 ]. The findings of the present study will provide researchers with opportunities to identify the correct drug(s) to combat COVID-19.…”

Recent advances in developing small-molecule inhibitors against SARS-CoV-2

“…4 ( 2 ) Arbidol In vitro 4.11 31.79 ChiCTR2000029573 NCT04252885 60 , 64 Fig. 4 ( 3 ) DRI-C23041 In vitro (pseudovirus) 5.6 ＞135 Preclinical 65 Fig. 4 ( 4 ) Cepharanthine In vitro 1.41 11.22 Preclinical 66 In vitro 0.13 ‒ Preclinical 78 In vitro 2.8 12.9 Preclinical 94 Fig.…”

“…DRI-C23041 [ Fig. 4 ( 3 )] inhibited SARS-CoV-2-S pseudovirus with IC 50 of 5.6 μmol/L ( Table 2 ) 65 .…”

SARS-CoV-2, Cardiovascular Diseases, and Noncoding RNAs: A Connected Triad

“…A first pharmacological strategy to reduce SARS-CoV-2 infectivity is blocking or reducing the interaction between Spike viral protein and host ACE2 receptor. One explored strategy, still to be fully proven, is in the utilization of small-molecule inhibitors (SMIs), which lack immunogenic side effects, is easily administered, and seems to be less strain-and mutation-sensitive compared with conventional antibodies [94].…”