Investigational Antiviral Study Finds Faster Clinical Improvement in Patients With COVID-19


Favipiravir is not approved by the FDA. It is being researched in the United States as a potential treatment of COVID-19.

Top-line results from a phase 3 trial of favipiravir, an investigational antiviral drug, found that patients with mild to moderate coronavirus disease 2019 (COVID-19) who received the drug had a 28.6% faster viral clearance compared to patients in the control arm.1

Favipiravir is a broad spectrum oral antiviral drug that functions by selectively inhibiting RNA-dependent RNA polymerase and the viral replication phase of COVID-19. It is being investigated in multiple international clinical trials, according to Glenmark Pharmaceuticals, a global, research-led pharmaceutical company that produces generic medications.1

Favipiravir is not approved by the FDA. However, the drug is being researched in the United States as a potential treatment of COVID-19. Those investigating this use of favipiravir includes a team at Stanford Medicine.2

In the phase 3 trial, according to Glenmark, patients in the favipiravir arm received 3600 mg tablets on day 1, and 800 mg tablets on day 2 or later, for a maximum of 14 days, in addition to standard supportive care. In total, 90 patients were deemed to have mild disease, while 60 patients had moderate disease. The primary efficacy endpoint was the speed of viral clearance, and the investigators found numerical improvements with a 28.6% faster viral clearance.1

In addition, the investigators noted a 40% faster achievement of “clinical cure,” which was defined as the physician’s assessment of normalization of clinical signs, with a statistically significant reduction in median time to clinical cure in the favipiravir treatment arm. By day 4, 69.8% of patients who received favipiravir achieved clinical cure, compared to 44.9% in the control arm. Furthermore, among patients who clinically deteriorated and required oxygen support, the investigators found that those receiving favipiravir had a longer median time to the first use of oxygen (5 days vs 2 days).1

Favipiravir was well-tolerated with no serious adverse events (SAE) nor were there deaths in the favipiravir treatment arm. One SAE occurred in the control arm and resulted in death due to clinical disease, attributed to the COVID-19 infection. Adverse events (AEs) were reported in 35.6% of patients in the favipiravir arm compared to 8% of the control arm, but most AEs were mild to moderate and none led to drug discontinuation of dosing adjustments. The most common AE was asymptomatic transient increases in uric acid.1

“I eagerly await the final analysis and results from other ongoing studies from across the globe,” said Zarir Udwadia, MD, DNB, FRCP, FCCP, a principal investigator, in a prepared statement. “Till then, I feel we have enough evidence to consider using favipravir in symptomatic COVID-19 patients who have mild to moderate infection.”1

The study at Stanford Medicine is in an early phase and, this month, investigators were aiming to enroll 120 patients recently diagnosed with COVID-19 who were not hospitalized. According to Marisa Holubar, MD, clinical associate professor of infectious disease and an investigator for the Stanford Medicine study, early-phase studies are important to inform larger clinical trials.2

A goal of the Stanford Medicine study is to understand if favipiravir shortens the life of the COVID-19 viral shedding, or the release of the virus into the environment from an infected person.2


  • Glenmark Announces Top-Line Results From Phase 3 Clinical Trial of Favipiravir in Patients with Mild to Moderate COVID-19 [news release]. Mumbai, India; July 22, 2020: Glenmark Pharmaceuticals. Accessed July 22, 2020.
  • White T. Stanford Medicine trial to test favipiravir for treating COVID-19 outpatients. Stanford Medicine news website. Published June 30, 2020. Accessed July 22, 2020.

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