Merck falls short in PhIII Covid-19 prophylaxis trial, joining Pfizer
Merck took another swing at bat to bolster its case for its Covid-19 antiviral — and that swing turned into yet another miss.
The pharma giant said Tuesday morning that its antiviral molnupiravir, branded as Lagevrio, failed to show “a statistically significant reduction in the risk of COVID-19 following household exposure to another individual with COVID-19” in a Phase III trial.
The study enrolled more than 1,500 participants — all who lived with someone who was newly diagnosed with Covid-19. That household member was also showing at least one symptom or sign of the disease, and had not had said symptoms for more than five days.
In short, the group taking Lagevrio was 23.6% less likely to be infected with Covid-19 than those who received placebo during the first 14 days of the study. However, Merck said that the primary endpoint was not met.
Merck now joins Pfizer after the Paxlovid maker failed its 3,000-patient trial in post-exposure prophylaxis last year. Pfizer saw risk reductions of 32% and 37%, depending on the duration a patient was on Paxlovid to prevent infection, but none of those numbers were statistically significant.
A Merck spokesperson told Endpoints News via email that the trial was testing the antiviral in adults who started out the study without Covid-19, per a negative test. The goal was to see how the antiviral would do in preventing patients on the antiviral treatment from contracting the disease.
Merck wrote that it plans to submit the full results from the study to be presented at an unnamed scientific meeting or for publication.
Lagevrio has been used far less than its competitor, Pfizer’s Paxlovid — Lagevrio was granted EUA one day after Paxlovid. However, that December 2021 authorization was only for cases in which other treatments were “not accessible or clinically appropriate.”
While Paxlovid reduced the risk of hospitalization and death due to Covid-19 by almost 90%, molnupiravir’s efficacy has hovered around 30%.
Despite the latest setback, Merck wrote that it will be doing further study on molnupiravir in potentially indications outside of Covid-19, citing the possibility of other infectious diseases such as RSV.
The FDA just recently axed the requirement for a positive test to get a prescription for either Paxlovid or Lagevrio — only requiring a mild-to-moderate Covid-19 diagnosis.