The Antiviral Mechanism of Action of Molnupiravir in Humans with COVID-19

Meaningful metrics of antiviral activity are essential for determining the efficacy of therapeutics in human clinical trials. Molnupiravir (MOV) is a broadly acting antiviral nucleoside analog prodrug that acts as a competitive alternative substrate for the SARS-CoV-2 RNA-dependent RNA polymerase (RdRp). We developed an assay, Culture-PCR, to better understand the impact of MOV therapy on infectious SARS-CoV-2. Culture-PCR revealed MOV eliminated infectious virus within 48 hours in the nasopharyngeal compartment, the upper airway location with the greatest levels of infectious virus. MOV therapy was associated with increases in mutations across the viral genome but select regions were completely unaffected, thus identifying regions where mutation likely abrogates infectivity. MOV therapy did not alter the magnitude or neutralization capacity of the humoral immune response, a documented correlate of protection. Thus, we provide holistic insights into the function of MOV in adults with COVID-19. ### Competing Interest Statement K.R.M. has received grant support from Ridgeback Biotherapeutics and Gilead Sciences. R.S.B. serves on the Scientific Advisory Board of Takeda, VaxArt, and Invivyd and has collaborations with Janssen Pharmaceuticals, Gilead, Chimerix, and Pardes Biosciences. A.L.G. reports contract testing from Abbott, Cepheid, Novavax, Pfizer, Janssen and Hologic, research support from Gilead, outside of the described work. T.P.S. reports collaborations with Gilead Sciences and contract testing from GSK and ViiV Healthcare and funding from NIH for a collaborative grant with Gilead Sciences. W.A.F. serves on adjudication committees for Janssen and Syneos and is a consultant to Roche and Merck & Co., Inc., Rahway, NJ, USA. W.P.P. has consulted for Drug Innovation Ventures at Emory University and Emory Institute of Drug Development (EIDD). W.P.P. is also an employee of Ridgeback Biotherapeutics. J.J.E. is a consultant to Merck & Co., Inc., Rahway, NJ, USA and GlaxoSmithKline and the chair of a data safety monitoring board for Adagio Pharmaceuticals. R.B. receives funding from the NIH on a partnership grant with Gilead Sciences Inc. D.A.W. serves on advisory boards and consults for Gilead Sciences Inc., ViiV Healthcare, Merck & Co., Inc., Rahway, NJ, USA, and Janssen. D.A.W. also receives grant support from Gilead Sciences Inc., ViiV Healthcare, and Merck & Co., Inc., Rahway, NJ, USA. W.H. also owns shares of Merck & Co., Inc., Rahway, NJ, USA. W.H. and W.P.P. are, along with others, presently named as coinventors of two pending provisional patent applications entitled Treatment of Viruses with Antiviral Nucleosides submitted on behalf of Ridgeback Biopharmaceuticals, Emory University, and Merck Sharp & Dohme LLC, a subsidiary of Merck & Co., Inc., Rahway, NJ, USA. ### Clinical Protocols ### Funding Statement Ridgeback Biotherapeutics and Merck & Co., Inc., Rahway, NJ, USA are jointly developing molnupiravir. Since licensed by Ridgeback Biotherapeutics, all funds used for the development of molnupiravir by Ridgeback Biotherapeutics have been provided by Wayne and Wendy Holman and Merck Sharp & Dohme LLC, a subsidiary of Merck & Co., Inc., Rahway, NJ, USA. W.A.F. and R.S.B. received grant support for this study. Salary support from NIH (U19 AI171292) supported T.P.S. in the generation of this manuscript. ### Author Declarations I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained. Yes The details of the IRB/oversight body that provided approval or exemption for the research described are given below: The study protocol was approved by Western IRB (WIRB). Participants were enrolled at ten sites across six states: North Carolina, California, Washington, Texas, Florida, and Louisiana. All study participants provided written informed consent. See study [NCT04405570][1] I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals. Yes I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance). Yes I have followed all appropriate research reporting guidelines, such as any relevant EQUATOR Network research reporting checklist(s) and other pertinent material, if applicable. Yes All data produced in the present study are available upon reasonable request to the authors [1]: /lookup/external-ref?link_type=CLINTRIALGOV&access_num=NCT04405570&atom=%2Fmedrxiv%2Fearly%2F2023%2F11%2F27%2F2023.11.21.23298766.atom