COVID-19 Antigen Rapid Test: scientists repurpose FDA-approved drug to fight all COVID-19 variants

Scientists repurpose FDA-approved drug to fight all COVID-19 variants

Several FDA-approved drugs -- including those for type 2 diabetes, hepatitis C and HIV -- significantly reduce SARS, according to a new study led by scientists at Penn State University. Replication ability of delta variants of CoV-2 in human cells. Specifically, the team found that the drugs inhibited certain viral enzymes, known as proteases, that are critical for the replication of SARS-CoV-2 in infected human cells.

"The SARS-CoV-2 vaccine targets the spike protein, but that protein is under strong selective pressure, as we've seen with Omicron," said Joyce Jose, associate professor of biochemistry and molecular biology at Penn State. It can mutate significantly. There is still an urgent need for therapeutics for SARS-CoV-2 that target parts of the virus other than the spike protein, which are less prone to evolution."

Previous studies have shown that two SARS-CoV-2 enzymes -- including the proteases of Mpro and PLpro -- are promising targets for antiviral drug development. For example, Pfizer's COVID-19 therapy Paxlovid targets Mpro. According to Jose, these enzymes are relatively stable; therefore, they are unlikely to rapidly develop resistance mutations.

Katsuhiko Murakami, a professor of biochemistry and molecular biology at Penn State, noted that these viral proteases are critical to the replication of SARS-CoV-2 in infected cells due to their ability to cleave or cleave proteins.

"SARS-CoV-2 produces long proteins, called polyproteins, from its RNA genome, which must be cleaved into individual proteins in an orderly fashion by these proteases, leading to the formation of functional viral enzymes and proteins that begin once inside the cell Viral replication," explained Murakami. "If you inhibit one of these proteases, you can stop the further spread of SARS-CoV-2 in infected people."

The findings were published Feb. 25 in the journal Communications Biology.

The team designed an assay to rapidly identify inhibitors of Mpro and PLpro proteases in living human cells.

"While other assays exist, the novel assay we designed can be performed in living cells, which allows us to simultaneously measure the toxicity of the inhibitor to human cells," Jose said.

The researchers used their assay to test a library of 64 compounds -- including inhibitors of HIV and hepatitis C proteases; cysteine proteases that occur in certain protozoan parasites; and dipeptidyl peptidases, A human enzyme involved in type 2 diabetes -- to test their ability to inhibit Mpro or PLpro. From these 64 compounds, the team identified 11 compounds that affected Mpro activity and five that affected PLpro activity with a cutoff point of 50% reduction in protease activity and 90% cell viability.

Anoop Narayanan, associate research professor of biochemistry and molecular biology, monitored the activity of these compounds using intravital confocal microscopy.

"We designed the experiment so that if the compound affected the protease, you would see fluorescence in certain areas of the cell," Narayanan said.

Next, the team evaluated the antiviral activity of 16 PLpro and Mpro inhibitors against the SARS-CoV-2 virus in the BSL-3 facility of Penn State's Eva J. Pell ABSL-3 Advanced Biological Research Laboratory and found that Eight of them had dose-dependent antiviral activity against SARS-CoV-2. Specifically, they found that Sitagliptin and Daclatasvir inhibited PLpro, while MG-101, Lycorine HCl, and Nelfinavir mesylate inhibited Mpro. Among them, the team found that MG-101 also hindered the virus's ability to infect cells by inhibiting protease processing of the spike protein.

"We found that when cells were pretreated with selected inhibitors, only MG-101 affected virus entry into cells," Narayanan said.

In addition, the researchers found that treating cells with a combination of Mpro and PLpro inhibitors had additional antiviral effects, providing greater inhibition of SARS-CoV-2 replication.

"Our study shows that in cell culture, if you combine Mpro and a PLpro inhibitor, you can have a stronger effect on the virus without increasing toxicity," Jose said. "The inhibitory effect of this combination is very potent. of."

To investigate the mechanism by which MG-101 inhibits Mpro protease activity, scientists including Manju Narwal, a postdoctoral scholar in biochemistry and molecular biology, used X-ray crystallography to obtain a high-resolution structure of MG-101 in complex with Mpro.

"We were able to see how MG-101 interacted with the active site of Mpro," Narwal said. "This inhibitor mimics the polyprotein and binds to the protease in a similar way, blocking the binding and cleavage of the protease to the polyprotein, an important step in viral replication."

Murakami added, "By understanding how the MG-101 compound binds to the active site, we can design new compounds that may be more effective."

In fact, the team is designing new compounds based on the structures they determined through X-ray crystallography. They also plan to test a combination of drugs they have shown effective in mice.

Although the scientists studied the delta variant of SARS-CoV-2, they said the drugs are likely to be effective against Omicron and future variants because they target parts of the virus that are unlikely to mutate significantly.

Jose said: "The development of broad-spectrum antiviral drugs against various coronaviruses is the ultimate therapeutic strategy for circulating and emerging coronavirus infections. Our study shows that repurposing certain FDA-approved drugs that inhibit Mpro and PLpro activity, which may be a useful strategy against SARS-CoV-2."

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