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A repurposed antibiotic shows promise as a COVID-19 treatment in mice. Christopher Pike/Bloomberg via Getty Images
  • There is still no cure for the coronavirus, which to date is responsible for more than 6 million deaths worldwide.
  • Researchers from the Pasteur Institute in Lille, France say an existing antibiotic shows promise repurposed as a potential treatment for the SARS-CoV-2 virus in a mouse model.
  • The existing drug is called clofoctol. Scientists plan to test it for COVID-19 in humans in a phase 3 clinical trial.

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Since the start of the COVID-19 pandemic, researchers have put much emphasis on the creation of the COVID-19 vaccine, as well as potential medications to treat the disease.

Current research efforts to find a therapeutic agent for coronavirus include the antiviral drugs molnupiravir and remdesivir, as well as an antimalarial drug called atovaquone.

However, there is still no cure for the coronavirus.

Now, researchers from the Pasteur Institute in Lille, France say the antibacterial drug clofoctol shows promise as a potential treatment for the SARS-CoV-2 virus that causes COVID-19 via a mouse model.

The study was recently published in the journal PLOS Pathogens.

Clofoctol is an antibiotic drug used for the treatment of bacterial respiratory tract infections. It is also sometimes used to prevent infections after throat, nose, and ear surgeries.

This is not the first time researchers have identified clofoctol as a repurposed drug for the treatment of other conditions. In May 2021, a study showed the antibiotic drug as a possible treatment for prostate cancer and neuroglioma.

And in May 2019, researchers identified clofoctol as a suppressant of glioma stem cells, which are the primary cause of malignant tumors in the central nervous system.

The idea of drug repurposing is certainly not new. However, the advent of the COVID-19 pandemic has placed an increased focus in looking at already developed and approved drugs as a possible remedy, rather than waiting the years it takes to develop a brand new medication.

According to Dr. Jean Dubuisson, head of the Center for Infection and Immunity of Lille at the Pasteur Institute, and co-lead author of this study, in the context of the COVID-19 pandemic, the objective of this study was to rapidly identify a drug compound that could potentially be tested in a clinical trial.

“Drug repurposing can accelerate the time for using it in humans since such a drug has already been tested for its toxicity and tolerability in humans,” he explained to MNT. “Developing de novo a new drug takes much more time because it needs chemical optimization, with a lot of preclinical validations, and it can take 10-15 years for such a development.”

Researchers identified clofoctol from a database of almost 2,000 approved drugs to find ones that showed antiviral activity against SARS-CoV-2.

“After the first screen, among the 1,942 compounds tested, we identified [21] molecules with potential antiviral activity against SARS-CoV-2,” Dr. Dubuisson explained. “However, only a limited number of these molecules, including clofoctol, were confirmed in additional experiments.”

“Clofoctol was finally chosen because of its pharmacological properties,” he added. “Indeed, this compound accumulates in human lungs at a concentration much higher than the concentrations showing antiviral activity in cell culture.”

Through the study, Dubuisson and his team tested the effectiveness of clofoctol both in vitro in cell cultures and within transgenic mice infected with SARS-CoV-2.

At the conclusion of the study, researchers found mice treated with clofoctol had a lower SARS-CoV-2 viral load in their lungs. Additionally, the mice had reduced lung inflammation.

Dubuisson said the next step for this research is to test clofoctol in humans via a phase 3 clinical trial.

Dr. Jimmy Johannes, pulmonologist and critical care medicine specialist at MemorialCare Long Beach Medical Center in Long Beach, CA, would also like to see human clinical trials emerge from what he told MNT was promising research.

“It’s one of those things where it’s good to see that people are looking for new antiviral treatments,” he added. “We just have to guard any excitement any time it’s not yet tested in humans.”

Dr. Johannes also believed it is a good idea to look at repurposing old drugs for new indications, such as COVID-19. “When we have an older drug, that usually means that we’ve done some studies or we have some experience using them,” he explained.

“Therefore, there is some safety data to use. There’s a little bit more confidence — when we find that it is positive and it might work — that it’s also probably safer than something that we haven’t tested before.”