News release reporting that the trial of molnupiravir with hospitalized patients (NCT04575584 (history)) has been discontinued because data indicates it is unlikely to demonstrate a clinical benefit in hospitalized patients. Results are not available yet. Interim results for the trial with outpatients show positive dose-dependent results for viral clearance.
Potential risks of molnupiravir include the creation of dangerous variants, and mutagenicity, carcinogenicity, teratogenicity, and embryotoxicity1-15. Multiple analyses have identified variants potentially created by molnupiravir16-20. Studies show significantly increased risk of acute kidney injury21, cardiovascular toxocity22, and neurological symptoms21. Treatment may increase viral rebound23,24.
1.
Swanstrom et al., Lethal mutagenesis as an antiviral strategy, Science, doi:10.1126/science.abn0048.
2.
Hadj Hassine et al., Lethal Mutagenesis of RNA Viruses and Approved Drugs with Antiviral Mutagenic Activity, Viruses, doi:10.3390/v14040841.
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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.
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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.
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Huntsman, M., An assessment of the reproductive toxicity of the anti-COVID-19 drug molnupiravir using stem cell-based embryo models, Master's Thesis, scholarspace.manoa.hawaii.edu/items/cd11342c-b4dc-44c0-8b44-ce6e3369c40b.
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Huntsman (B) et al., Detection of developmental toxicity of the anti-COVID-19 drug molnupiravir using gastruloid-based in vitro assays, Toxicological Sciences, doi:10.1093/toxsci/kfaf093.
7.
Zibat et al., N4-hydroxycytidine, the active compound of Molnupiravir, promotes SARS-CoV-2 mutagenesis and escape from a neutralizing nanobody, iScience, doi:10.1016/j.isci.2023.107786.
8.
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.
9.
Gruber et al., Molnupiravir increases SARS‐CoV‐2 genome diversity and complexity: A case‐control cohort study, Journal of Medical Virology, doi:10.1002/jmv.29642.
10.
Marikawa et al., An active metabolite of the anti-COVID-19 drug molnupiravir impairs mouse preimplantation embryos at clinically relevant concentrations, Reproductive Toxicology, doi:10.1016/j.reprotox.2023.108475.
11.
Rahman, M., Elucidation of the DNA repair mechanisms involved in the repair of DNA damage caused by the Arabinosides and Anti-COVID-19 drugs, tokyo-metro-u.repo.nii.ac.jp/records/2000972.
12.
Zhou et al., β-D-N4-hydroxycytidine Inhibits SARS-CoV-2 Through Lethal Mutagenesis But Is Also Mutagenic To Mammalian Cells, The Journal of Infectious Diseases, doi:10.1093/infdis/jiab247.
13.
Chamod et al., Molnupiravir Metabolite--N4-hydroxycytidine Causes Cytotoxicity and DNA Damage in Mammalian Cells in vitro: N4-hydroxycytidine Induced Cytotoxicity DNA Damage, Asian Medical Journal and Alternative Medicine, 23:3, asianmedjam.com/index.php/amjam/article/view/1448.
14.
Standing et al., Randomized controlled trial of molnupiravir SARS-CoV-2 viral and antibody response in at-risk adult outpatients, Nature Communications, doi:10.1038/s41467-024-45641-0.
15.
Mori et al., Reactive oxygen species-mediated cytotoxic and DNA-damaging mechanism of N4-hydroxycytidine, a metabolite of the COVID-19 therapeutic drug molnupiravir, Free Radical Research, doi:10.1080/10715762.2025.2469738.
16.
Focosi et al., The fitness of molnupiravir-signed SARS-CoV-2 variants: imputation analysis based on prescription counts and GISAID analyses by country, Intervirology, doi:10.1159/000540282.
17.
Sanderson et al., A molnupiravir-associated mutational signature in global SARS-CoV-2 genomes, Nature, doi:10.1038/s41586-023-06649-6.
18.
Fountain-Jones et al., Effect of molnupiravir on SARS-CoV-2 evolution in immunocompromised patients: a retrospective observational study, The Lancet Microbe, doi:10.1016/S2666-5247(23)00393-2.
19.
Kosakovsky Pond et al., Anti-COVID drug accelerates viral evolution, Nature, doi:10.1038/d41586-023-03248-3.
21.
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.
22.
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.
Merck et al., 15 Apr 2021, preprint, 1 author, trial NCT04575584 (history).
Late treatment
is less effective
is less effective
