A tale of two drugs: Molnupiravir and Paxlovid

The orally administered antiviral drug Lagevrio or molnupiravir (MOV) and the combination antiviral drug nirmatrelvir/ritonavir or Paxlovid (PAX) have been shown to reduce the likelihood of hospitalization and death for high-risk patients with COVID-19. Clinical studies, including those comparing PAX and MOV, were reviewed; both drugs are effective in reducing morbidity and mortality in COVID patients, although PAX generally appears to be more efficacious. Both drugs received Emergency Use Authorization in the United States for mild to moderate COVID-19 infection, while only PAX has subsequently been given full FDA approval. The principal disadvantage of PAX is that it interacts with many commonly used drugs, while MOV does not. The purpose of this review is to summarize current information and knowledge about these two drugs. The two drugs have completely different mechanisms of action. PAX inhibits viral replication while MOV induces viral replication errors that are expected to lead to viral inactivation. There is, however, the potential that MOV also could mutate host DNA and cause the virus to mutate into variants with new features. The package insert for MOV states that patients should be notified of relevant toxicity issues before administration. Sensitive mutation detection/analysis studies, such as error corrected Next Generation Sequencing (ecNGS) or HPRT mutation detection assays, in MOV-treated patients are needed to establish the safety of MOV.