- In an effort to combat SARS-CoV-2, and with the rise of other coronaviruses likely, experts are looking for existing drugs that can fight these infections.
- A leprosy drug called clofazimine has shown promise against SARS-CoV-2 in hamsters.
- Clofazimine blocks the ability of SARS-CoV-2 to enter cells and replicate via RNA.
- The drug has also shown promise against Middle East respiratory syndrome (MERS) in laboratory experiments.
SARS-CoV-2, which is the virus that causes COVID-19, is not the only zoonotic coronavirus. In fact, it is the third to have emerged since the turn of the century. It was preceded by severe respiratory syndrome (SARS) in 2003 and MERS in 2012.
There are likely to be more coronaviruses if the recent past is any indication. However, there are not currently many drugs that can effectively combat them.
Researchers have been racing to identify existing drugs that may be of use in this fight, with one team last year identifying 21 existing drugs as showing promise. Among these was a leprosy drug called clofazimine, which has proven effective against both SARS and MERS in laboratory experiments.
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A new study from researchers at Sanford Burnham Prebys Medical Discovery Institute in San Diego, CA, and the University of Hong Kong in Pok Fu Lam suggests that it may also be useful in treating COVID-19.
Clofazimine exhibits antiviral properties against SARS-CoV-2 and limits the extreme inflammatory response that commonly occurs with COVID-19.
The study has undergone peer review and will soon appear in edited form in the journal Nature.
A drug that is well-known and safe
If researchers confirm clofazimine’s efficacy, experts could immediately deploy the drug against SARS-CoV-2 and COVID-19.
The Food and Drug Administration (FDA) have already approved it for use against leprosy, and it is on the World Health Organization (WHO)’s Model List of Essential Medicines. Experts have thoroughly vetted the drug for safety, though it is not currently available for sale in the United States.
Co-senior study author Dr. Sumit K. Chanda — of the Immunity and Pathogenesis Program at Sanford Burnham Prebys — says, “Clofazimine is an ideal candidate for a COVID-19 treatment. It is safe, affordable, easy to make, taken as a pill and can be made globally available.”
Dr. Chanda explains, “We hope to test clofazimine in a phase 2 clinical trial as soon as possible for people who test positive for COVID-19 but are not hospitalized,” adding:
“Since there is currently no outpatient treatment available for these individuals, clofazimine may help reduce the impact of the disease, which is particularly important now as we see new variants of the virus emerge and against which the current vaccines appear less efficacious.”
The effect of clofazimine
In the study, the researchers administered clofazimine to hamsters with SARS-CoV-2 and prophylactically (preventively) to other hamsters that did not yet have the virus.
Both groups that the researchers treated with clofazimine had less SARS-CoV-2 in their lungs after taking the drug.
Clofazimine also prevented the often deadly inflammatory overreaction that commonly occurs in humans. This is called the “cytokine storm.”
Co-senior study author Dr. Ren Sun, of the University of Hong Kong, reports, “The animals that received clofazimine had less lung damage and lower viral load, especially when receiving the drug before infection.”
Dr. Sun adds, “Besides inhibiting the virus, there are indications that the drug also regulates the host response to the virus, which provides better control of the infection and inflammation.”
The study suggests that clofazimine fights SARS-CoV-2 by doing two things: blocking the virus’s entry into cells and disrupting RNA replication of the virus.
A partner for remdesivir and more
The researchers also found that clofazimine, when they administered it to hamsters, worked synergistically with remdesivir. This is the most prominent drug currently in use as a COVID-19 treatment.
Since clofazimine is affordable and easy to make, it may help stretch the limited — and comparatively expensive — supply of remdesivir.
Considering experts’ concerns regarding future coronaviruses, it is equally exciting that clofazimine seems to prevent the in vitro replication of MERS in human lung tissue.
“Potentially most importantly, clofazimine appears to have pan-coronavirus activity, indicating [that] it could be an important weapon against future pandemics,” says co-senior study author Dr. Kwok-Yung Yuen, of Infectious Diseases at the University of Hong Kong.
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