Study finds possible treatment for COVID-19 in leprosy drug, La Jolla scientist says

Sumit Chanda, director of the immunity and pathogenesis program for the Sanford Burnham Prebys Medical Discovery Institute in La Jolla, is the co-senior author of a new study that indicated a leprosy drug may be able to treat cases of COVID-19 if detected early.

Chanda and his team are now gathering funding for Phase 2 trials of clofazimine, hoping to run human testing to determine the drug’s efficacy and broader application as a go-to COVID treatment.

The study — which tested clofazimine in hamsters infected with SARS-CoV-2, the coronavirus that causes COVID-19 — showed that clofazimine “blocks two critical steps of viral replication,” Chanda said. “The first step is getting into the cell, and clofazimine interferes with the virus’s ability to get into the cell.”

“The second step,” he said, “is it blocks the ability to have the virus make copies of itself … and propagate.”

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Discovery of clofazimine’s potential as a COVID-19 treatment came from a 2020 study in which Chanda’s lab looked at 12,000 known drugs for any that might combat the disease, attempting to shortcut the 10 to 17 years it normally takes to build a new drug. At the time, his team narrowed the field to about 30 potentially promising drugs.

“The idea was we can pull a needle in the haystack, and this was the needle and so we’re very excited about this,” he said.

Phase 2 trials would administer clofazimine to a few hundred to a thousand volunteers who have recently tested positive for the virus, along with a placebo group, Chanda said.

“We’re hoping that … people taking clofazimine should have a drastic reduction in ICU admittance and hospitalization, which is really what we’re trying to treat here with COVID,” he said. “The extreme cases are the ones that we worry about.”

Chanda said his team is reaching out to various governmental and non-governmental funding sources to secure the Phase 2 trials.

The Phase 1 trials were “safety trials” held long ago, when clofazimine was first approved by the Food and Drug Administration, he said.

If clofazimine were proved to work, it would be an “ideal candidate” as a COVID-19 treatment, he said.

“One of the key things about developing antivirals … is that the earlier you give a drug, the better it can work,” Chanda said. “It’s hard to give a drug early when you require IV administration, like what you do for remdesivir,” currently one of few treatments for COVID-19 (the others are antibody treatments, which also require an IV).

Chanda said clofazimine, if successful in clinical trials, would be most beneficial in cases of “post-exposure prophylaxis,” either when a person is exposed to someone with COVID-19 or tests positive but doesn’t have symptoms severe enough to warrant a hospital stay.

“You can just have your doctor call in a prescription,” he said. “And it’ll likely work better because you’ve taken it earlier.”

Chanda said another “interesting thing that we found is that [clofazimine] works very well with remdesivir,” cutting the amount of the latter drug needed to 1/20 of the amount normally used, with “the same effect.” That means countries can extend their supply of remdesivir, he said.

Having a known cocktail of drugs can aid the battle against variants of the disease, he added. “It becomes much harder for a virus to escape multiple drugs.”

Another boon, he said, is clofazimine’s cost. “Remdesivir costs somewhere around $1,500 to $2,500 per use,” he said, while the clofazimine pills are about $1.50 each.

The financial accessibility is “really important,” Chanda said. “None of us are safe until all of us are saved.”

Clofazimine can be widely distributed not only in “underserved communities in the U.S. but also in the Third World. This is a ... worldwide disease and we need to have treatment options for everybody.”

So far, clofazimine has shown that it “classically works against at least the four different coronaviruses that we’ve tested,” Chanda said, meaning the drug has “broad spectrum activity” and would be applicable to future viruses.

“We think this could be an important drug to have at the ready for the next coronavirus,” he said. “The vaccine was incredible — one of the most amazing medical accomplishments that I’ve witnessed in my lifetime — but it still does take time to roll out vaccines. So if you have drugs at the ready, you can mitigate the impact of an emergent pandemic. … We’re going to be better prepared for the next one.”

Still, he cautioned against stocking up on clofazimine for the moment. “We have to show that it works in humans, of course. We’re really hoping that it will make a difference in human disease.”

The co-senior and co-corresponding study authors with Chanda are Ren Sun of the University of Hong Kong and UCLA and Kwok-Yung Yuen of the University of Hong Kong. ◆