Merck and Ridgeback’s COVID-19 pill fails to prevent infection within households

Merck – known as MSD outside the US and Canada – has reported that its COVID-19 pill, jointly developed with Ridgeback, did not significantly reduce the risk of infections in those living with someone recently diagnosed with the virus.

Lagevrio (molnupiravir) is already approved or authorised to treat certain adults who have been diagnosed with COVID-19 in several markets, including the US, UK and China, but is not authorised anywhere for the prevention of the virus.

The phase 3 MOVe-AHEAD trial evaluated the safety and efficacy of Lagevrio compared to placebo in preventing the spread of SARS-CoV-2 within households.

The trial enrolled over 1,500 participants who were randomised to receive either the drug or placebo orally every 12 hours for five days.

Results showed that those treated with Lagevrio were 23.6% less likely to develop COVID-19 than those given a placebo until day 14, failing to meet the primary endpoint of the trial, Merck said.

The safety profile of Lagevrio was generally consistent with that observed in previously reported clinical studies and post-authorisation experience in the treatment of COVID-19.

Dr Dean Li, president of Merck Research Laboratories, said: “Results from this post-exposure prevention study are scientifically interesting as we continue to learn more about COVID-19.”

Li added that, because MOVe-AHEAD was not a treatment trial, these latest results will not impact the efficacy and safety data observed for Lagevrio in the treatment of mild-to-moderate COVID-19.

"We remain focused on our ongoing efforts to bring Lagevrio as a treatment to appropriate high-risk patients with COVID-19 where its use is authorised or approved, as well as to further study the ways it may benefit patients with other infectious diseases, such as RSV,” he said.

Lagevrio was originally authorised for emergency use in December 2021 by the US Food and Drug Administration, which recently removed the need for a positive test in a bid to increase access to the drug.

The authorisation was based on results from the phase 3 MOVe-OUT trial, in which Lagevrio significantly reduced the risk of hospitalisation or death of at-risk COVID-19 patients.

Robert Davis, chief executive officer and chairman of Merck, said at the time that the authorisation was "an important milestone in the fight against COVID-19”.