Merck says its experimental pill to treat COVID-19 cuts the risk of hospitalization and death in half

Merck announced Friday that an experimental pill it developed to treat COVID-19 reduced the risk of hospitalization and death by nearly half in a clinical trial.

An independent board of experts monitoring the trial recommended the study be stopped early because of the positive results, a significant and telling step in a pharmaceutical study.

Merck and partner Ridgeback Biotherapeutics said in a news release they would apply for emergency use authorization for the drug, molnupiravir, in the United States as soon as possible. It would be the first antiviral pill for COVID-19.

A simple, easy-to-prescribe pill that prevents mild and moderate cases of COVID-19, the illness caused by the coronavirus, from turning into dire episodes has been one of the missing pieces of the medical armamentarium to fight the virus.

Monoclonal antibodies, treatments that have kept people out of the hospital, are expensive, tricky to manufacture and cumbersome to administer, requiring infusions or injections. Vaccines have been remarkably effective, but access is limited in much of the world.

"We always believed antivirals, especially an oral antiviral, would be an important contribution to the pandemic," Daria Hazuda, vice president of infectious diseases and vaccine discovery at Merck, said in an interview. "Keeping people out of the hospital is incredibly important, given the emergence of variants and the continued evolution of the virus."

The data has not yet been published or peer reviewed.

» READ MORE: Nursing home workers aren’t getting vaccinated — prompting worries about the elderly, staffing, and a coming federal mandate

Merck has already begun producing molnupiravir. The small brown capsules must be taken twice a day for five days. The company predicts it will make 10 million courses of treatment by the end of the year. The U.S. government made an advance purchase of 1.7 million doses of the drug at a cost of $1.2 billion.

The biggest impact of the drug might be in the rest of the world, where vaccine availability is low and monoclonal antibody treatments may be impractical or unavailable. Merck has licensed its drug to five Indian generic drug manufacturers to speed up availability in low- and middle-income countries, many of which have had limited access to vaccines.

The company said it would use a "tiered pricing approach," pricing the drug to reflect countries' ability to pay for the drug.

A global trial of the pill enrolled 775 people with mild or moderate COVID-19. Participants had at least one risk factor for severe COVID-19, such as obesity or advanced age. They had to start the drug regimen within five days of symptom onset and be unvaccinated.

Half of study participants received the drug and half received a placebo. No deaths were reported among people receiving the drug, but eight deaths were recorded among those who received a placebo. The rate of hospitalization and death in people who received the drug was 7.3 percent — about half the level for those who received a placebo.

Those results, showing the drug afforded significant protection, led an independent safety board to suggest halting the trial.

» READ MORE: Penn RNA scientists win Philly’s Scott award for research used in COVID-19 vaccines

Laboratory and animal experiments suggest the pill may be effective against known variants, including delta. Unlike vaccines or antibodies that target specific proteins on the surface of the virus, molnupiravir works by introducing nonsense mutations and garbling the coronavirus's genetic code. That means it may be more resistant to mutation, and may even work on other coronaviruses or RNA viruses.

"As a virologist, that's one of the things I find particularly exciting," Hazuda said. "Now, we've demonstrated the potential to have a drug that could work across multiple coronaviruses. I don't think this is the last pandemic in our lifetime, and having something readily available that is active would be amazing."

Pfizer is also developing an oral antiviral drug, and announced this week it was initiating a later-stage clinical trial testing the drug’s ability to prevent illness in people exposed to the coronavirus. Atea Pharmaceuticals is also working on an oral antiviral with pharmaceutical giant Roche.