Facilitating the process of screening for COVID-19 antiviral drugs – Jacobs School of Medicine and Biomedical Sciences

From left to right, Uddhav Timilsina, PhD; Thomas Melendy, Ph.D.; and Rama Dey-Rao, PhD; are the main developers of the new screening method.

Posted November 30, 2021

A team of researchers from the Jacobs School of Medicine and Biomedical Sciences has developed a new high-throughput screening method designed to rapidly screen for antiviral candidates against the SARS-CoV2 virus.

Described in a document published in October in Antiviral Research, the screening method is designed to identify a certain class of antiviral drugs that inhibit the major protease (Mpro), a specific target of SARS-CoV2.

Develop a faster way to screen for antiviral drugs

Twenty months after the start of the pandemic, the need for targeted antiviral drugs against COVID-19 is clear, given the virus’s global persistence, its ability to rapidly mutate into new variants, and the possibility that it could potentially develop strains. resistant to existing drugs or vaccines.

But developing antivirals can take many years; the examples of hepatitis C, HIV and the human papillomavirus (HPV) all illustrate the myriad difficulties associated with such efforts. The combination of antivirals that ultimately proved effective in curing the hepatitis C virus, for example, had been in development for decades.

The new study was developed by a team of scientists from the University of Buffalo led by Rama Dey-Rao, PhD, senior author and assistant research professor, and Thomas Melendy, PhD, senior author and professor, both in the Department of microbiology and immunology.

Researchers at the Jacobs School reported that their screening test served several important purposes:

  • it expresses fully mature and functional SARS-CoV-2 Mpro, while most other efforts have expressed slightly modified forms, which are not optimal for drug testing
  • he can evaluate Mpro function in living human cells
  • the system is designed so that inhibition of Mpro produces a positive signal in a living cell; systems that produce a negative signal require additional screening to identify false positives caused by cellular toxicity

Sharing resources during the global pandemic

“Our contribution was to create this screening method so that several, if not thousands, of compounds active against SARS-CoV2 can be detected rapidly in a few hours or days as opposed to weeks or months using others. methods, ”says Melendy, who also has a date. in the biochemistry department.

He adds that UB, like most research universities, has agreed to make resources like this one for the pandemic readily available to others.

The new screening method identifies antivirals that inhibit an enzyme called the main protease, which is needed for SARS-CoV2 to replicate. Once the virus enters a cell, the Mpro is essential in order to be able to produce the other viral enzymes necessary to function inside the infected cell to create more viruses and viral spread.

Faster search for protease inhibitors

The advantage of the UB screening method is that it eliminates several steps usually involved in screening for antiviral drugs.

Melendy explains that in most cases, viral enzyme inhibitors are developed by finding and designing molecules that first target the viral enzyme in a test tube. From there, further testing needs to be done to determine its toxicity, its ability to get inside human cells and, once inside, its effectiveness.

After that, he continues, the drug candidates must be tested against viral infection of human cells, which requires a biosafety level 3 facility requiring high-level containment due to the dangers of working with a virus. living. Because testing for live viruses is dangerous, it is very expensive and takes longer. Therefore, it does not lend itself to rapid screening of large collections of compounds.

“On the other hand, the system we have developed only uses the M viruspro, not all of the infectious virus expressed in human cells, so it “isolates” that viral target, ”says Melendy. “When the Mpro is functional, the cells will express a biosensor that is cleaved by the Mpro. But if an effective inhibitor of the M viruspro (a potential antiviral drug) is added to these cells, the biosensor is not cleaved, and the cells fluoresce red.

“Since there is no live virus involved in the high throughput screening, the system does not require expensive and risky BSL-3 bio-containment,” notes Dey-Rao.

“And since the whole process takes place inside cultured living cells, it demonstrates that all of the inhibitors identified must be functional in living cells,” adds Melendy.

Advantageous to treat with “cocktails” of drugs

Once an inhibitor is identified, the next steps would be to test it against viral infection of human cells, in animal models, and then in clinical trials.

Uddhav Timilsina, PhD, postdoctoral associate working in a group led by Spyridon Stavrou, PhD, assistant professor of microbiology and immunology, verified that this cellular system works and that the only drug tested that inhibited Mpro in the UB test showed a similar inhibition of SARS-CoV2 infection of human lung cells.

The ability to effectively screen for thousands of compounds is essential, as a single antiviral drug is usually not effective enough. As seen with HIV and HCV, the SARS-CoV2 virus will likely also require combinations or “cocktails” of antivirals.

“Antivirals are not ‘perfect’ and viruses can mutate and become resistant to antivirals,” says Melendy. “Therefore, it is more efficient to develop more than one drug against specific viral target proteins. It is also very beneficial to treat individuals with a “cocktail” of more than one antiviral drug. “

He adds that patients with persistent infections with certain strains of HCV are now effectively cured using a combination of antivirals, inhibitors of hepatitis C viral genome replicase – another type of viral enzyme – and the hepatitis C viral protease.

Melendy notes that the antiviral Merck SARS-CoV2 that has been submitted to the United States Food and Drug Administration is an inhibitor of the SARS-CoV2 genome replicase.

“By combining it with a SARS-CoV-2 M inhibitorpro would probably provide more effective therapy, ”he says.

SARS-CoV2 is expected to become endemic

Melendy adds that most public health experts expect SARS-CoV2 to become endemic in the world’s population, continue to circulate, causing disease and death; then antiviral drugs, as well as vaccines, will be a key element in dealing with this pandemic.

“Having more than one antiviral drug that works against more than one viral target will be essential in dealing with epidemics, especially if drug-resistant variants appear, as such viruses would only be resistant to one. only class of antivirals, ”he said.

Along with Dey-Rao, Melendy, Stavrou and Timilsina, other Jacobs School co-authors are:

The work was funded in part by the National Institutes of Health, a COVID Research Fellowship from the SUNY Research Foundation, the Jacobs School, the Department of Microbiology and Immunology, and donor contributions to the UB Foundation’s Papillomavirus Research Fund. (which was redirected to SARS-CoV2 research during the ongoing pandemic).

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