Laboratory studies show that Merck & Co’s (MRK.N) experimental oral COVID-19 antiviral drug, molnupiravir, is likely to be effective against known variants of the coronavirus, including the dominant, highly transmissible Delta, the company said on Wednesday.
Since molnupiravir does not target the spike protein of the virus – the target of all current COVID-19 vaccines – which defines the differences between the variants, the drug should be equally effective as the virus continues to evolve, said Jay Grobler, head of infectious disease and vaccines at Merck.
Molnupiravir instead targets the viral polymerase, an enzyme needed for the virus to make copies of itself. It is designed to work by introducing errors into the genetic code of the virus.
“Data shows that the drug is most effective when given early in the course of infection,” Merck said.
The U.S. drugmaker tested its antiviral against nasal swab samples taken from participants in early trials of the drug. Delta was not in wide circulation at the time of those trials, but molnupiravir was tested against lab samples of the variant behind the latest surge in COVID-19 hospitalizations and deaths.
Merck said earlier this year that a small, mid-stage trial found that after five days of molnupiravir treatment, none of the patients taking various doses of the drug tested positive for infectious virus, while 24% of placebo patients did have detectable levels.
Merck is currently conducting two Phase III trials of the antiviral it is developing with Ridgeback Biotherapeutics – one for treatment of COVID-19 and another as a preventive.
“Merck anticipates that the Phase III treatment study will finish in early November,” Grobler said.
On the other hand, according to a report, an independent group of medical experts monitoring the trial recommended stopping it early because the interim results were so strong. Company executives said they are in discussions with the Food and Drug Administration and plan to submit the data for review in the coming days.
“It exceeded what I thought the drug might be able to do in this clinical trial,” said Dr. Dean Li, vice president of Merck research. “When you see a 50% reduction in hospitalization or death that’s a substantial clinical impact.”
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Side effects were reported by both groups in the Merck trial, but they were slightly more common among the group that received a dummy pill. The company did not specify the problems.
Earlier study results showed the drug did not benefit patients who were already hospitalized with severe disease.
The trial enrolled nonhospitalized COVID-19 patients who have had symptoms for no more than five days and are at risk for severe disease.
The latest analysis was presented during IDWeek, the annual meeting of infectious disease organizations, including the Infectious Diseases Society of America.
Shares of Merck were up 2.3% at $75.04 on Wednesday afternoon on the New York Stock Exchange.
