Analysis of the Pioneer trial for favipiravir suggesting benefit in women and patients achieving target plasma concentrations. Only 17% of patients reached target plasma concentrations, with this subgroup showing trends toward improved outcomes (p=0.07 for primary endpoint, p=0.11 for mortality). The trial appears to have been significantly limited by inadequate dosing, with the vast majority of patients not reaching target drug concentrations.
Potential risks of favipiravir include kidney injury1-3, liver injury2-5, cardiovascular events5,6, pulmonary toxicity6,7, and mutagenicity, carcinogenicity, teratogenicity, embryotoxicity, and the creation of dangerous variants8-14.
1.
Abdulaziz et al., Clinical Features and Prognosis of Acute Kidney Injury in Hospital-Admitted Patients with COVID-19 in Egypt: A Single-Center Experience, Mansoura Medical Journal, doi:10.58775/2735-3990.1433.
2.
Ülger et al., Experimental evaluation of favipiravir (T-705)-induced liver and kidney toxicity in rats, Food and Chemical Toxicology, doi:10.1016/j.fct.2025.115472.
3.
El-Fetouh et al., Experimental Studies on Some Drugs Used in Covid-19 Treatment (Favipiravir and Dexamethasone) in Albino Rats, Journal of Advanced Veterinary Research, 13:10, www.advetresearch.com/index.php/AVR/article/view/1635.
4.
Almutairi et al., Liver Injury in Favipiravir-Treated COVID-19 Patients: Retrospective Single-Center Cohort Study, Tropical Medicine and Infectious Disease, doi:10.3390/tropicalmed8020129.
5.
Siby et al., Temporal Trends in Serious Adverse Events Associated with Oral Antivirals During the COVID-19 Pandemic: Insights from the FAERS Database (2020–2023), Open Forum Infectious Diseases, doi:10.1093/ofid/ofaf695.1825.
6.
Ozhan et al., Evaluation of the cardiopulmonary effects of repurposed COVID-19 therapeutics in healthy rats, Scientific Reports, doi:10.1038/s41598-025-31048-4.
7.
Ülger (B) et al., Evaluation of the effects of favipiravir (T-705) on the lung tissue of healty rats: An experimental study, Food and Chemical Toxicology, doi:10.1016/j.fct.2025.115235.
8.
Zhirnov et al., Favipiravir: the hidden threat of mutagenic action, Journal of microbiology, epidemiology and immunobiology, doi:10.36233/0372-9311-114.
9.
Waters et al., Human genetic risk of treatment with antiviral nucleoside analog drugs that induce lethal mutagenesis: the special case of molnupiravir, Environmental and Molecular Mutagenesis, doi:10.1002/em.22471.
10.
Hadj Hassine et al., Lethal Mutagenesis of RNA Viruses and Approved Drugs with Antiviral Mutagenic Activity, Viruses, doi:10.3390/v14040841.
11.
Shum, C., An investigational study into the drug-associated mutational signature in SARS-CoV-2 viruses, The University of Hong Kong, PhD Thesis, hub.hku.hk/handle/10722/344396.
12.
Shiraki et al., Convenient screening of the reproductive toxicity of favipiravir and antiviral drugs in Caenorhabditis elegans, Heliyon, doi:10.1016/j.heliyon.2024.e35331.
Wawman et al., 14 Sep 2024, peer-reviewed, 11 authors.
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