Background: Despite vaccination, many remain vulnerable to COVID-19 and its complications. Oral antivirals to prevent COVID-19 progression are vital. Based upon perceived potency and clinical efficacy, favipiravir is widely used to treat COVID-19. Evidence from large randomized controlled trials (RCT) is lacking.

Methods: In this multicenter double-blinded placebo-controlled RCT, adults with early mild-to-moderate COVID-19 were 1:1 randomized to favipiravir or placebo. The study evaluated time to sustained clinical recovery (TT-SCR), COVID-19 progression, and cessation of viral shedding.

Results: Of 1187 analyzed patients across 40 centers, 83.3% were Hispanic, 89.0% unvaccinated, 70.3% SARS-CoV-2 seronegative, and 77.8% had risk factors for COVID-19 progression. The median time from symptom presentation and from positive test to randomization was three and two days, respectively. There was no difference in TT-SCR (median of 7 days for both groups; p = 0.80), COVID-19 progression [11 patients each (1.9% vs. 1.8%); p = 0.96], time to undetectable virus [median = 6 days, 95% CI (6-8) vs. 7 days, 95% CI (6-9)], or in undetectable virus by end of therapy (73.4% vs. 72.3%; p = 0.94). Outcomes were consistent across the analyzed sub-groups. Adverse events were observed in 13.8% and 14.8% of favipiravir-treated and placebo-treated subjects, respectively. Uric acid elevation was more frequent among favipiravir-treated subjects (19.9% vs. 2.8%).

Conclusions: Favipiravir was well tolerated but lacked efficacy in TT-SCR, progression to severe COVID-19, or cessation of viral shedding and should not be used to treat patients with COVID-19.