The anti-HIV Drug Nelfinavir Mesylate (Viracept) is a Potent Inhibitor of Cell Fusion Caused by the SARS-CoV-2 Spike (S) Glycoprotein Warranting further Evaluation as an Antiviral against COVID-19 infections

Abstract

<jats:title>Abstract</jats:title><jats:p>Coronaviruses belong to a group of enveloped, positive-single stranded RNA viruses that are known to cause severe respiratory distress in animals and humans. The current SARS coronavirus-2 (SARS CoV-2) pandemic has caused more than 2,000,000 infections globally and nearly 200,000 deaths. Coronaviruses enter susceptible cells via fusion of the viral envelope with the plasma membrane and/or via fusion of the viral envelope with endosomal membranes after endocytosis of the virus into endosomes. Previous results with SARS and MERS CoV have shown that the Spike (S) glycoprotein is a major determinant of virus infectivity and immunogenicity. Herein, we show that expression of SARS CoV-2 S (S-n) glycoprotein after transient transfection of African green monkey kidney (Vero) cells caused extensive cell fusion in comparison to limited cell fusion caused by the SARS S (S-o) glycoprotein. S-n expression was detected intracellularly and on transfected Vero cell surfaces and caused the formation of very large multinucleated cells (syncytia) by 48 hours post transfection. These results are in agreement with published pathology observations of extensive syncytial formation in lung tissues of COVID-19 patients. This differential S-n versus S-o-mediated cell fusion suggests that SARS-CoV-2 is able to spread from cell-to-cell much more efficiently than SARS effectively avoiding extracellular spaces and neutralizing antibodies. A systematic screening of several drugs for ability to inhibit S-n and S-o cell fusion revealed that the FDA approved HIV-protease inhibitor, nelfinavir mesylate (Viracept) drastically inhibited S-n and S-o-mediated cell fusion in a dose-dependent manner. Complete inhibition of cell fusion was observed at a 10 micromolar concentration. Computational modeling and <jats:italic>in silico</jats:italic> docking experiments suggested the possibility that nelfinavir may bind inside the S trimer structure, proximal to the S2 amino terminus directly inhibiting S-n and S-o-mediated membrane fusion. Also, it is possible that nelfinavir mesylate acts on cellular processes to inhibit S proteolytic processing. These results warrant further investigations of the potential of nelfinavir mesylate as an antiviral drug, especially at early times after SARS-CoV-2 symptoms appear.</jats:p>

Potential antiviral options against SARS-CoV-2 infection

“…Molecular docking studies predicted nelfinavir binding site on SARS-CoV-2 protease (Mothay and Ramesh, 2020). Nelfinavir could also inhibit cell fusion caused by the SARS-CoV-2 S glycoprotein (https://doi.org/10.1101/2020.04.06.026476) (Musarrat et al, 2020). It also inhibits CHIKV, DENV, HCV, HSV-1, and SARS infections (https://doi.org/10.1039/C5RA14469H) (Kalu et al, 2014;Toma et al, 2009;Yamamoto et al, 2004).…”

A Generalized Overview of the Possible Pharmacotherapy and Treatments against SARS-CoV-2

“…Nelfinavir mesylate is generated as an anti-human immunodeficiency virus (HIV) protease inhibitor, originally established to be used in combination with HIV targeting antivirals through different mechanisms. With the advancement of recently developed antiviral combinations for HIV, nelfinavir mesylate reportedly inhibited severe Acute Respiratory Syndrome (SARS) replication and cytopathic effects in cell culture [15,70]. Previously, the structure and function S glycoprotein of SARS in transient transfectionmembrane fusion assessment were investigated [71,72].…”

“…Previously, the structure and function S glycoprotein of SARS in transient transfectionmembrane fusion assessment were investigated [71,72]. SARS CoV-2 S (Sn) has been reported to cause profound S-mediated membrane fusion compared to the cell fusion produced by transient expression of SARS (So) [70]. The probability of binding nelfinavir to the S2 amino terminus within the S trimer was revealed by in-silico docking experiments thus; it may straightly prevent the formation of the heptadrepeat complex that results in S-mediated membrane fusion [70].…”

Nelfinavir for COVID19: Summary of basic science data and initial clinical experience

“…Research team from National Institute of Infectious Disease of Japan found that nelfinavir is the most potent protease inhibitor against SARS-CoV-2, 3-5 times more potent than lopinavir/ritonavir (9). Several computational models also confirmed that nelfinavir can bind SARS-CoV-2 main protease (Mpro) at the Glu166 position (7,8), and this interaction is quantitatively greater than that of lopinavir and ritonavir (10). Furthermore, a more recent computational model suggested that nelfinavir can also attack the SARS-CoV-2 Spike protein, inhibiting viral entry into the cell (8).…”

“…Nelfinavir is an oral antiretroviral protease inhibitor used in the therapy and prevention of human immunodeficiency virus. In vitro data from multiple groups have shown that nelfinavir has activity against SARS-CoV-2 (7,8). Research team from National Institute of Infectious Disease of Japan found that nelfinavir is the most potent protease inhibitor against SARS-CoV-2, 3-5 times more potent than lopinavir/ritonavir (9).…”