Using error-corrected sequencing for evaluating mutagenicity of molnupiravir in humans.

Publication date: Jan 09, 2026

Molnupiravir (MOV) is a prodrug of N-hydroxycytidine (NHC), an analog of the endogenous ribonucleoside cytidine that can be administered orally. MOV is used for treating patients infected by SARS-CoV-2, the coronavirus responsible for COVID-19. MOV and NHC are mutagenic in bacterial and in mammalian cell cultures, yet both chemicals have been negative or equivocal in nonclinical in vivo models of mutagenesis. We designed and validated a novel error-corrected sequencing (ECS) method for detecting single basepair substitutions in tissue samples obtained from genetically heterogeneous humans. The software used for this ECS method is available for free from a public on-line repository and it is suitable for analysis of in vivo and in vitro derived samples collected in various experimental scenarios. We recruited two groups of patients having COVID-19 one to three years ago, one group that received a full course of MOV therapy and the other group (matched for age and COVID-19 diagnosis date) that did not receive MOV. Using the ECS method, we determined the frequencies of basepair substitutions in nucleated cells isolated from peripheral blood of the patients. There was no observed difference in the frequency of mutations, the types of mutations, or mutational spectra between the MOV and the control groups. Also, the spectra of mutations in the MOV group did not show any evidence of the mutational signature expected from exposures to MOV or NHC based on data from mammalian cell culture models. Within the limits of this study, the dose of MOV authorized for the treatment of COVID-19 under emergency use authorization appears to have no mutational consequences for treated patients.

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