Molnupiravir

Molnupiravir, sold under the brand name Lagevrio, is an antiviral medication that inhibits the replication of certain RNA viruses. It is used to treat COVID‑19 in those infected by SARS-CoV-2. It is taken by mouth.

Molnupiravir is a prodrug of the synthetic nucleoside derivative N⁴-hydroxycytidine and exerts its antiviral action by introducing copying errors during viral RNA replication.

Molnupiravir was originally developed to treat influenza at Emory University by the university's drug innovation company, Drug Innovation Ventures at Emory (DRIVE), but was reportedly abandoned for mutagenicity concerns. It was then acquired by the Miami-based company Ridgeback Biotherapeutics, which later partnered with Merck & Co. to develop the drug further.

Based on positive results in placebo-controlled double-blind randomized clinical trials, molnupiravir was approved for medical use in the United Kingdom in November 2021. In December 2021, the US Food and Drug Administration (FDA) granted an emergency use authorization (EUA) to molnupiravir for use in certain populations where other treatments are not feasible. The emergency use authorization was only narrowly approved (13–10) because of questions about efficacy and concerns that molnupiravir's mutagenic effects could create new variants that evade immunity and prolong the COVID‑19 pandemic. In September 2023, molnupiravir's viral mutagenicity was confirmed to contribute to circulating SARS-CoV-2 genomic variation in a study of global SARS CoV 2 isolates after 2022: molnupiravir-specific genomic changes were more common, especially where molnupiravir had been used.

In the UK, molnupiravir is indicated for treatment of mild to moderate COVID‑19 in adults with a positive SARS-COV-2 diagnostic test and who have at least one risk factor for developing severe illness.

In the US molnupiravir is unapproved but is authorized under an EUA for emergency use for the treatment of adults with mild-to-moderate COVID‑19 who are at high risk for progression to severe COVID‑19, including hospitalization or death, and for whom alternative COVID‑19 treatment options approved or authorized by FDA are not accessible or clinically appropriate.

Molnupiravir also shows potential antiviral activity against Middle East respiratory syndrome coronavirus (MERS-CoV), influenza virus, respiratory syncytial virus (RSV), bovine viral diarrhea virus (BVDV), hepatitis C virus (HCV), Ebola virus (EBOV), feline coronavirus (FCoV) and enteroviruses.

Use during pregnancy is not recommended. There are no human data on use during pregnancy to assess the risk of adverse maternal or fetal outcomes. Based on animal data, the drug may cause fetal harm.