Molnupiravir appears to be active against the SARS-CoV-2 variant Omicron based on data from 6 preclinical studies.

The in vitro studies, which were independently conducted in 6 countries, used cell-based assays to evaluate the antiviral activity of molnupiravir against Omicron, in addition to other variants of concern.

“These findings from multiple independent in vitro studies showing that molnupiravir has consistent antiviral activity against Omicron, the primary variant circulating globally, provide additional confidence in the potential of molnupiravir as an important treatment option for certain adults with mild to moderate COVID-19 who are at high risk for progressing to severe disease,” said Dr Dean Y. Li, president, Merck Research Laboratories.

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Molnupiravir is a nucleoside analogue that inhibits SARS-CoV-2 replication by viral mutagenesis. In December 2021, the oral antiviral received the Food and Drug Administration’s (FDA) Emergency Use Authorization based on data from the phase 3 MOVe-OUT trial  ( Identifier: NCT04575597). The study compared the efficacy and safety of molnupiravir to placebo in nonhospitalized adults with symptom onset within 5 days of randomization.

Results showed that 6.8% (n=48/709) of patients treated with molnupiravir were either hospitalized or died through day 29 following randomization compared with 9.7% (n=68/699) of patients treated with placebo (absolute risk reduction, 3.0%; 95% CI, 0.1-5.9; nominal P =.0218), corresponding to a relative risk reduction of 30% (relative risk, 0.70; 95% CI, 0.49-0.99).

Among the entire study population, 55% of patients had viral sequencing data. The 3 most common SARS-CoV-2 variants included Delta (58.1%), Mu (20.5%), and Gamma (10.7%). Findings showed that the efficacy benefit was consistent among patients infected with these variants.

“Based on its mechanism of action, along with these new findings demonstrating in vitro activity across multiple variants, including Omicron, we anticipate that molnupiravir will continue to be active against variants of concern and an important tool in the fight against COVID-19,” said Wendy Holman, chief executive officer, Ridgeback Biotherapeutics.


Merck and Ridgeback’s molnupiravir, an investigational oral antiviral COVID-19 medicine, demonstrated activity against Omicron variant in in vitro studies. News release. January 28, 2022.

This article originally appeared on MPR