Stanford Medicine trial to test favipiravir for treating COVID-19 outpatients

Researchers want to determine whether favipiravir, an oral drug, is effective in reducing the severity of symptoms and shortening the duration of COVID-19.

- By Tracie White

Aruna Subramanian is investigating an antiviral drug, favipiravir, to see if it reduces symptoms and viral shedding in COVID-19 outpatients.
Steve Fisch

Stanford Medicine researchers are launching a clinical trial to test whether an oral drug can reduce symptoms and viral shedding in people with COVID-19.

The researchers aim to enroll 120 participants, beginning July 6, who have been recently diagnosed with the disease but not been hospitalized.

Favipiravir, an antiviral medication, was first approved to treat influenza in Japan. Researchers are hoping it will be effective in reducing the severity of symptoms and in shortening the duration of COVID-19, which could help limit spread of the coronavirus, said Aruna Subramanian, MD, clinical professor of medicine.

“We hope that this drug can help to reduce transmission within families, groups and schools,” said Subramanian, one of the investigators for the study. “Plus, it would be really nice to have pills that can be given early on to make people get better faster.”

Yvonne Maldonado, MD, professor of pediatrics and of health research and policy, is the principal investigator for the double-blind, placebo-controlled trial.

The drug has not been approved by the Food and Drug Administration. There are other trials investigating the drug, but this is the first time it will be tested in outpatients in the U.S., Subramanian said. It has been approved to treat COVID-19 in Russia, China and India. 

 “Many really important studies are going on right now to help us understand how to emerge from this pandemic,” said Marisa Holubar, MD, clinical associate professor of infectious disease and an investigator for the study. “These early-phase studies are important to inform larger clinical trials. We need to understand if favipiravir shortens the duration of viral shedding. It could be a key to protecting both ourselves and the broader community.”

Yvonne Maldonado is the principal investigator of the double-blind, placebo-controlled trial.
Steve Fisch

Viral shedding is the release of a virus into the environment from an infected person.

Stanford participated in earlier clinical trials that found that another antiviral, remdesivir, was effective in treating coronavirus patients. That drug has since been approved for use in the U.S. but is not available orally and, so far, can be administered only intravenously and only to those in a hospital.

 “Favipiravir could be very important for symptom relief, especially for patients with mild cases who can have symptoms for a long time,” Subramanian said. “We’ve seen a number of symptoms continue, such as coughs, shortness of breath, fatigue.” 

At a molecular level, the drug works by blocking a viral enzyme that makes viral RNA, halting the virus’s ability to replicate itself, Holubar said. Like other antivirals, it’s presumed to work better the earlier it’s prescribed.

Researchers are enrolling those who have been diagnosed with COVID-19 within the past 72 hours. Each participant will receive either a 10-day course of favipiravir or a placebo, and they will be evaluated for health outcomes over 28 days. 

People can enroll by emailing

About Stanford Medicine

Stanford Medicine is an integrated academic health system comprising the Stanford School of Medicine and adult and pediatric health care delivery systems. Together, they harness the full potential of biomedicine through collaborative research, education and clinical care for patients. For more information, please visit

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