News Release

Mefloquine: A promising drug 'soldier' in the battle against COVID-19

Scientists propose the repurposing of anti-malarial drug mefloquine to fight the novel coronavirus

Peer-Reviewed Publication

Tokyo University of Science

Mefloquine for COVID-19 (1 of 2)

video: Scientists propose the repurposing of anti-malarial drug mefloquine to fight the novel coronavirus. view more 


Early 2020 saw the world break into what has been described as a "war-like situation": a pandemic, caused by the severe acute respiratory syndrome-related coronavirus 2 (SARS-CoV-2), the likes of which majority of the living generations across most of the planet have not ever seen. This pandemic has downed economies and resulted in hundreds of thousands of deaths. At the dawn of 2021, vaccines have been deployed, but before populations can be sufficiently vaccinated, effective treatments remain the need of the hour.

Thus, other than fast-tracking research into novel drugs, scientists have also been exploring their arsenals of existing medicines in a bid to find anything that could work against COVID-19. Some approved drugs, like hydroxychloroquine, lopinavir, and interferon, have already been put to clinical use against SARS-CoV-2 without well establishing their clinical efficacies, due to the severity of the pandemic. Subsequent randomized trials have not been able to yield a consensus on the efficacy of these drugs. Only remdesivir has been approved for clinical use against severe COVID-19, although its efficacy is still being debated.

In a breakthrough study, a team of scientists--comprising Dr. Koichi Watashi, Kaho Shionoya, Masako Yamasaki, Dr. Hirofumi Ohashi, Dr. Shin Aoki, Dr. Kouji Kuramochi, and Dr. Tomohiro Tanaka from Tokyo University of Science (along with scientists from the National Institute of Infectious Diseases, Kyushu University, The University of Tokyo, Kyoto University, Japanese Foundation for Cancer Research, and Science Groove Inc.)--have identified an anti-malarial drug, mefloquine (which is incidentally a derivative of hydrochloroquine), that is effective against SARS-CoV-2. Their findings are published in Frontiers in Microbiology.

Detailing their modus operandi, lead scientist in the team Dr. Watashi says, "To identify drugs with higher antiviral potency than existing antivirals, we first screened approved anti-parasitic/anti-protozoal drugs. We found that mefloquine had the highest anti-SARS-CoV-2 activity among the tested compounds. Upon testing it against other quinoline derivatives, such as hydrochloroquine, in a cell line mimicking the cell-based environments of human lung cells, we found it to be better."

The team further explored mefloquine's mechanism of action. Dr. Watashi explains the process, "In our cell assays, mefloquine readily reduced the viral RNA levels when applied at the viral entry phase but showed no activity during virus-cell attachment. This shows that mefloquine is effective on SARS-COV-2 entry into cells after attachment on cell surface."

Thus, to bolster mefloquine's anti-viral activity, the scientists looked into the possibility of combining it with a drug that inhibits the replication step of SARS-CoV-2: Nelfinavir. Interestingly, they observed that the two drugs acted in "synergy" and the drug combination showed greater anti-viral activity than either showed alone, without being toxic to the cells in the cell lines themselves.

The scientists also mathematically modelled the effectiveness of mefloquine to predict its potential real-world impact if applied to treat COVID-19. What they predicted was that mefloquine could reduce the overall viral load in affected patients to under 7% and shorten the 'time-till-virus-elimination' by 6.1 days.

This study must of course be succeeded by clinical trials, but the world can hope that mefloquine becomes a drug used to effectively treat patients with COVID-19.



Title of original paper: Mefloquine, a Potent Anti-severe Acute Respiratory Syndrome-Related Coronavirus 2 (SARS-CoV-2) Drug as an Entry Inhibitor in vitro
Journal: Frontiers in Microbiology

About the Tokyo University of Science

Tokyo University of Science (TUS) is a well-known and respected university, and the largest science-specialized private research university in Japan, with four campuses in central Tokyo and its suburbs and in Hokkaido. Established in 1881, the university has continually contributed to Japan's development in science through inculcating the love for science in researchers, technicians, and educators.

With a mission of "Creating science and technology for the harmonious development of nature, human beings, and society", TUS has undertaken a wide range of research from basic to applied science. TUS has embraced a multidisciplinary approach to research and undertaken intensive study in some of today's most vital fields. TUS is a meritocracy where the best in science is recognized and nurtured. It is the only private university in Japan that has produced a Nobel Prize winner and the only private university in Asia to produce Nobel Prize winners within the natural sciences field.

About Dr. Koichi Watashi from Tokyo University of Science

Dr. Koichi Watashi is a Visiting Professor at Graduate School of Science and Technology, Tokyo University of Science, Japan. Dr. Watashi also works as the Director, Division of Drug Development, Research Center for Drug and Vaccine Development, at National Institute of Infectious Diseases, Japan. He is an expert in virology, with over 20 years of experience in researching molecular mechanisms underlying virus proliferation and corresponding anti-viral agents. He has over 140 publications in international academic journals to his credit. He is the recipient of several prestigious awards like The Young Investigator Award of The Japanese Cancer Association, Sugiura Memorial Incentive Award of The Japanese Society for Virology, etc.

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