Phenothiazines as dual inhibitors of SARS-CoV-2 main protease and COVID-19 inflammation

Abstract

COVID-19, caused by the severe acute respiratory coronavirus 2 (SARS-CoV-2) currently has no treatment for acute infection. The main protease (Mpro) of SARS-CoV-2 is an essential enzyme for viral replication and an attractive target for disease intervention. The phenothiazine moiety has demonstrated drug versatility for biological systems, including inhibition of butyrylcholinesterase, a property important in the cholinesterase anti-inflammatory cascade. Nineteen phenothiazine drugs were investigated using in silico modelling techniques to predict binding energies and inhibition constants (Ki values) with SARS-CoV-2 Mpro. Since most side-effects of phenothiazines are due to interactions with various neurotransmitter receptors and transporters, phenothiazines with few such interactions were also investigated. All compounds were found to bind to the active site of SARS-CoV-2 Mpro and showed Ki values ranging from 1.30 to 52.4 µM. Nine phenothiazines showed inhibition constants <10 µM. The compounds with limited interactions with neurotransmitter receptors and transporters showed micromolar (µM) Ki values. Docking results were compared with remdesivir and showed similar interactions with key residues Glu-166 and Gln-189 in the active site. This work has identified several phenothiazines with limited neurotransmitter receptor and transporter interactions and that may provide the dual action of inhibiting SARS-CoV-2 Mpro to prevent viral replication and promote the release of anti-inflammatory cytokines to curb viral-induced inflammation. These compounds are promising candidates for further investigation against SARS-CoV-2.

Phenothiazines Inhibit SARS-CoV-2 Entry through Targeting Spike Protein

“…Thus, further research is warranted to evaluate more detailed mechanisms of phenothiazines to inhibit the entry of SARS-CoV-2 besides inhibiting CTSL cleavage. Theoretically, phenothiazines as a class of compounds seem not that specific as they were also reported to bind numerous other molecular targets such as SARS-CoV-2 M pro [ 43 ] and neuropilin-1 [ 33 ]. Additionally, a few studies have reported that the potential antiviral effects of phenothiazines may be associated with their ability to inhibit viral binding to plasma membrane receptors [ 44 , 45 , 46 ].…”

Dual inhibition of coronavirus Mproand PLproenzymes by phenothiazines and their antiviral activity

“…In a drug-repurposing study several phenothiazine-containing drugs approved by the FDA for the treatment of other medical conditions have been shown to inhibit spike protein-mediated entry of SARS-CoV-2 into cells [Hashizume et al, 2023]. Previous in - silico docking studies identified certain phenothiazines with strong predicted binding to the SARS-CoV-2 M pro active site [Forrestall et al, 2021]. Here, we expand on this concept and demonstrate that some novel phenothiazine urea compounds inhibit both M pro and PL pro or SARS-CoV-2 and have broad antiviral action against other coronaviruses.…”