Treatment options for Covid-19 are urgently needed as the total number of confirmed cases globally rises to 550,000 on Friday and the US becomes the country with the most confirmed cases, at over 86,000. One of the potentially quickest ways to find treatment is to test substances already approved or in development for other indications.
The influenza antiviral favipiravir, marketed as Avigan by Fujifilm Toyama in Japan, was tested in clinical trials with Covid-19 patients in China and showed a shorter viral clearance time than the control group that received the anti-HIV combo opinavir/ritonavir, marketed as Kaletra by AbbVie.
Unlike many influenza antivirals that target proteins on the surface of the virus, like Roche’s Tamiflu (oseltamivir phosphate), favipiravir targets the viral RNA polymerase, making it a potential treatment for Covid-19 if the SARS-CoV-2 RNA polymerase is similar enough to the influenza polymerase. In the clinical study conducted by the National Clinical Research Center for Infectious Diseases in Shenzhen, two 1,600mg doses of favipiravir on the first day and two doses of 600mg for the following 13 days, in addition to interferon-alpha aerosol inhalation (five million units twice daily), led to faster viral clearance than the lopinavir/ritonavir group, with a median of 4 days versus 11 days, respectively, aswell as improvement in chest imaging.
However, the small sample size of 340 participants, the comparison with lopinavir/ritonavir, whose efficacy to treat SARS-CoV-2 is questionable as reported in a separate clinical trial, as well as the addition of interferon-alpha without controlling for its efficacy separately, should lead to caution about the results until more data are available.
As for other Covid-19 treatment options being investigated, Gilead’s remdesivir, currently in Phase III in the US and China, is arguably the most promising drug and led to such strong demand for compassionate use that Gilead had to restrict access to pregnant women and children. Additionally, due to increasing pressure building up from non-profit public interest groups worrying about high prices and a long-term monopoly, Gilead asked the FDA to pull remdesivir’s orphan drug designation.
Further, chloroquine, the malaria drug touted by President Trump to be effective against Covid-19, has only showed mixed clinical results so far, and increasing demand is complicating access for people using chloroquine routinely to treat autoimmune diseases like lupus. Furthermore, high demand led India to ban the export of chloroquine, which could result in future shortages.
The coronavirus pandemic makes the slow progression of clinical studies feel even longer, but highlights the importance of good data derived from carefully controlled trials, which are critical for distinguishing justified from unjustified claims of a drug’s efficacy and safety, and furthermore shows that the entire world must work together to provide access to drugs and find a cure soon.