Clinical trials conducted in China have returned promising results for a treatment for patients infected with COVID-19, using an existing antiviral compound that has been used against similar viruses.
Typically used to treat new strains of influenza, favipiravir is an antiviral drug produced by Fujifilm Toyama Chemical that has been approved for use against RNA viruses like SARS-CoV-2, the virus that causes the COVID-19 disease, including influenza viruses, West Nile virus, yellow fever and ebola. Its use in clinical trials was approved by Chinese authorities last month, and has been tested against SARS-CoV-2 in two separate trials in the Chinese cities of Wuhan and Shenzhen.
“It has a high degree of safety and is clearly effective in treatment,” according to Zhang Xinmin, an official at China’s science and technology ministry. Favipiravir is also known as favilavir, as well as its brand-name Avigan, and was originally developed as a replacement for the Tamiflu flu treatment.
To date, COVID-19 has infected over 222,000 people worldwide, and killed nearly 10,000. Within the past few weeks the virus, a pathogen 20 to 30 times more deadly than the seasonal flu, has spread rapidly throughout the globe, resulting in the self-quarantine of entire nations, the closure of once-open borders, and heavy restrictions on international air travel.
The Shenzhen trial involved patients infected with COVID-19, with those treated with favipiravir showing negative results when tested for the virus after an average of four days, compared to the average of 11 days for patients not treated with the drug. The same trial also showed improvements in the lung x-rays of 91 percent of favipiravir-treated patients, contrasting with only 62 percent from the control group.
In the Wuhan trial, patients treated with favipiravir saw their fevers shortened to 2.5 days from the average 4.2 days if left untreated.
The drug works by interrupting the virus’s ability to replicate at the genetic level, preventing the spread of an infection. Unfortunately, the drug does not combat the virus itself—viruses are only genetically active when actively infecting a host cell—meaning that it cannot remove an existing infection. This is suspected to be the cause behind the poor results reported by a clinical trial being conducted on patients with severe symptoms in Japan.
“We’ve given Avigan to 70 to 80 people, but it doesn’t seem to work that well when the virus has already multiplied,” according to a source from Japan’s Ministry of Health. This same limitation appears to have been behind the poor performance of similar drugs that had previously been tested against HIV.
Government approval in Japan for full-scale use of favipiravir against COVID-19 could be cleared as early as May, although the ministry spokesperson cautioned that delays in clinical research results could also delay the approval process.