Pfizer said that its trial will enroll 1,140 non-hospitalized adults diagnosed with the SARS-CoV-2 infection who are not at risk of severe illness. The patients in the trial will be given the experimental pill and a low dose of ritonavir, an older medication used in combination treatments for HIV infection. The drug, known as PF-07321332, is designed to block the activity of a key enzyme that helps the virus multiply.
The company began a different trial of PF-07321332 in July, in adults with COVID-19 infection who are at high risk of becoming severely ill due to underlying conditions. The company expects initial results from the study in the coming fall. If the trial is successful, Pfizer said it would file for a potential emergency use authorization by the fourth quarter.
Merck, meanwhile, said that its new trial will study the drug molnupiravir to prevent COVID-19 among adults in the same household as someone diagnosed with symptomatic infection. The drug is an antiviral designed to introduce errors into the RNA of the virus, eventually preventing it from replicating. Merck and its partner, Ridgeback Biotherapeutics are already conducting a late-stage trial of the treatment in non-hospitalized patients.
Merck also said in June that the government agreed to pay about $1.2 billion for 1.7 million courses of molnupiravir, if proven to work, and if authorized by regulators. The company is expected to file for U.S. emergency use authorization in the second half of 2021 at the earliest. Early trial results for molnupiravir yielded promising results, and experts believe it could help cut back on the time that infected individuals remain positive for the virus.
Pfizer, Merck, and Swiss pharmaceutical Roche Holding AG have made the most progress in developing the first antiviral pill to treat or prevent COVID-19. To date, the only approved antiviral treatment for COVID-19 in the U.S. is Gilead Science Inc's. intravenous drug Veklury (remdesivir). (Related: Study: Pfizer vaccine less effective against COVID-19 Delta variant.)
Roche and its partner, Atea Pharmaceuticals in June said that early data from the trial of their experimental oral antiviral, AT-527, showed that it lowered the viral load in hospitalized patients.
What is molnupiravir?
The new oral drug that Merck is developing works by stopping the replication of multiple RNA viruses, including SARS-CoV-2. Researchers are currently investigating the drug as a potential treatment for COVID-19 in humans. In previous animal research, the drug was found to be able to suppress SARS-CoV-2 within 24 hours, making them hopeful about the results.
There is currently no oral or outpatient medication to treat people who have been infected with COVID-19. Molnupiravir could prove to be a game-changer based on its effectiveness.
Jamie Alan, Ph.D., and assistant professor of pharmacology at the Michigan State University says that the reduction in positive viral cultures is "great," but it is unclear at this point how or what that will translate in the real world. "Whether this will decrease deaths or disease severity would really be the true measures of success," Alan said.
Richard Watkins, MD, an infectious disease physician and a professor of internal medicine at the Northeast Ohio Medical University called the results interesting. "I hope the upcoming trials, which will include more patients, will also show beneficial effects," he said.
Watkins also noted that an effective and easy-to-use medication could make it easier to treat people earlier in their illness. The results are preliminary, but experts say the development is a step in the right direction.
"It is exciting to potentially have an oral antiviral agent with activity against SARS-CoV-2," Watkins said.
Read more updates about COVID-19 at Pandemic.news.
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