An international team of researchers found that three commonly used antiviral and antimalarial drugs are effective in vitro in preventing replication of SARS-CoV-2, the virus that causes COVID-19. The work also highlights the need to test compounds against multiple cell lines to rule out false negative results.
The team, which included researchers at North Carolina State University and Collaborations Pharmaceuticals, looked at three antiviral drugs that have been shown to be effective against Ebola and the Marburg virus: tilorone, quinacrine and pironaridine.
“We were looking for compounds that could block the virus from entering the cell,” says Ana Puhl, senior scientist at Collaborations Pharmaceuticals and corresponding co-author of the research. “We chose these compounds because we know that other antivirals that work successfully against Ebola are also effective inhibitors of SARS-CoV-2.”
The compounds were tested in vitro against SARS-CoV-2, as well as against the common cold virus (HCoV 229E) and the murine hepatitis virus (MHV). The researchers used a variety of cell lines that represented potential targets for SARS-CoV-2 infection in the human body. They infected the cell lines with the different viruses and then looked at how the compounds prevented viral replication in the cells.
The results were mixed, with the effectiveness of the compounds depending on whether they were used in human-derived cell lines versus monkey-derived cell lines, known as Vero cell lines.
“In human-derived cell lines, we found that all three compounds functioned similarly to remdesivir, which is currently being used to treat COVID-19,” says Frank Scholle, associate professor of biology at NC State and co-author of the research. “However, they were not at all effective in Vero cells.”
“The researchers saw similar results when these compounds were first tested against Ebola,” says Sean Ekins, CEO of Collaborations Pharmaceuticals and co-corresponding author of the research. “They were effective on human-derived cell lines, but not on Vero cells. This is important because Vero cells are one of the standard models used in this type of test. In other words, different cell lines can have different responses to a compound. He points to the need to test compounds on many different cell lines to rule out false negatives. “
The next steps in the research include testing the effectiveness of the compounds in a mouse model and working harder to understand how they inhibit viral replication.
“One of the most interesting findings here is that these compounds not only prevent the virus from potentially binding to cells, but they can also inhibit viral activity because these compounds are acting on lysosomes,” said Puhl. “Lysosomes, which are important for the normal functioning of the cell, are hijacked by the virus to enter and leave the cell. So, if this mechanism is stopped, it will not be able to infect other cells ”.
“It is also interesting that these compounds are effective not only against SARS-CoV-2, but also against related coronaviruses,” says Scholle. “This can give us an initial advantage in therapies as new coronaviruses emerge.”
The job appears in ACS Omega and was supported in part by the NC State Institute of Comparative Medicine and the National Institutes of Health. NC State graduate students, James Levi and Nicole Johnson, as well as Ralph Baric, from the University of North Carolina at Chapel Hill, contributed to the work. Other collaborating institutions were: Instituto Oswaldo Cruz and Universidade Estadual de Campinas, both in Brazil; Utah State University; the University of Maryland; and SRI International.
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Note to editors: Here is a summary.
“Repurposing the Ebola and Marburg Virus Inhibitors Tilorone, Quinacrine, and Pyronaridine: In Vitro Activity against SARS-CoV-2 and Potential Mechanisms”
IT HURTS: 10.1021 / acsomega.0c05996
Authors: Ana Puhl, Sean Ekins, Collaborations Pharmaceuticals; Frank Scholle, James Levi, Nicole Johnson, NC State University; et al
Published: March 12, 2021 in ACS Omega
Summary:
Severe acute respiratory coronavirus 2 (SARS-CoV-2) is a newly identified virus that resulted in more than 2.5 million deaths worldwide and more than 116 million cases worldwide in March 2021. Inhibitors of small molecules that reverse the severity of the disease have proved difficult to discover. One of the main approaches that has been widely applied in an effort to accelerate drug translation is the reuse of drugs. Some drugs have shown in vitro activity against the Ebola virus and demonstrated activity against SARS-CoV-2 in vivo. Most notably, RNA polymerase targeting remdesivir has demonstrated in vitro activity and efficacy in the early stage of the disease in humans. Testing other small molecule drugs that are active against the Ebola virus (EBOVs) seems like a reasonable strategy to assess its potential for SARS-CoV-2. Previously, we reused pyronaridine, tilorone and quinacrine (from malaria, influenza and use of antiprotozoa, respectively) as inhibitors of Ebola and Marburg viruses in vitro in HeLa and EBOV cells adapted to mice in mice in vivo. We have already tested these three drugs on several cell lines (VeroE6, Vero76, Caco-2, Calu-3, A549-ACE2, HUH-7 and monocytes) infected with SARS-CoV-2, as well as other viruses (including MHV and HCoV 229E ). The compilation of these results indicated a considerable variability in the antiviral activity observed in the cell lines. We found that tilorone and pironaridine inhibited virus replication in A549-ACE2 cells with IC 50 values of 180 nM and IC 50 of 198 nM, respectively. We used microscale thermophoresis to test the binding of these molecules to the spike protein, and tilorone and pironaridine bind to the protein in the spike receptor binding domain with Kd values of 339 and 647 nM, respectively. Human Cmax for pyronaridine and quinacrine is greater than the IC50 observed in A549-ACE2 cells. We also provide new insights into the mechanism of these compounds, which is likely to be smooth.