Oxidative DNA Damage by N4-hydroxycytidine, a Metabolite of the SARS-CoV-2 Antiviral Molnupiravir

Abstract Molnupiravir is an antiviral agent recently used for treating coronavirus disease 2019 (COVID-19). Here, we demonstrate that N4-hydroxycytidine (NHC), a molnupiravir metabolite, treated with cytidine deaminase (CDA) induced Cu(II)-mediated oxidative DNA damage in isolated DNA. A colorimetric assay revealed hydroxylamine generation from CDA-treated NHC. The site specificity of DNA damage also suggested involvement of hydroxylamine in the damage. Furthermore, Cu(I) and H2O2 play an important role in the DNA damage. We propose oxidative DNA damage via CDA-mediated metabolism as a possible mutagenic mechanism of NHC, highlighting the need for careful risk assessment of molnupiravir use in therapies for viral diseases, including COVID-19. N 4-hydroxycytidine (NHC) is an active metabolite of the SARS-CoV-2 antiviral molnupiravir. NHC treated with cytidine deaminase induced Cu(II)-mediated generation of reactive oxygen species and DNA damage, which is proposed as a new mutagenic mechanism of NHC.