Results were announced from a phase 3 study evaluating the efficacy and safety of molnupiravir for postexposure prophylaxis for prevention of COVID-19.

The multicenter, randomized, double-blind, placebo-controlled MOVe-AHEAD study ( Identifier: NCT04939428) enrolled over 1500 participants 18 years of age and older who resided in the same household with someone who tested positive for SARS-CoV-2, had at least 1 sign or symptom of COVID-19, and had not had those signs and symptoms for more than 5 days. Individuals who received the first dose of a COVID-19 vaccine more than 7 days prior to enrollment, previously had COVID-19 within the past 6 months, or were showing any signs or symptoms of COVID-19 were excluded from the study.

Participants were randomly assigned to receive molnupiravir 800mg orally or placebo every 12 hours for 5 days. Findings showed that while treatment with molnupiravir reduced the likelihood of developing COVID-19 by 23.6% through day 14 compared with placebo, the study missed the primary endpoint failing to achieve a statistically significant reduction in risk of COVID-19 following household exposure to another individual with COVID-19.

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The safety profile of molnupiravir was consistent with that seen in previous studies and post authorization data in COVID-19 treatment. Molnupiravir is currently marketed under the brand name Lagevrio and is authorized for emergency use for the treatment of certain adults who have been diagnosed with mild to moderate COVID-19.

“Results from this postexposure prevention study are scientifically interesting as we continue to learn more about COVID-19,” said Dr Dean Y. Li, president, Merck Research Laboratories. “This was not a treatment study and these results do not impact the efficacy and safety data observed in our phase 3 MOVe-OUT trial for the treatment of mild to moderate COVID-19.”

Final analysis from the MOVe-OUT trial showed that treatment with molnupiravir reduced the risk of hospitalization or death by 30% in at-risk patients with mild to moderate COVID-19.


Merck provides update on phase 3 MOVe-AHEAD Trial evaluating Lagevrio™ (molnupiravir) for post-exposure prophylaxis for prevention of COVID-19. News release. Merck. Accessed February 21, 2023.

This article originally appeared on MPR