Updated on December 22, 2021.
One day after the U.S. Food and Drug Administration (FDA) cleared the emergency use of the Pfizer antiviral pill for the treatment of COVID-19, the agency authorized a second pill made by Merck. If the milestone decisions are approved by the U.S. Centers for Disease Control and Prevention (CDC), the oral medications will become the first at-home treatments for COVID-19.
People ages 12 and older who are at high risk for severe disease are eligible for the Pfizer drug within five days of developing mild-to-moderate symptoms. People ages 18 and older who meet the same criteria are eligible for the Merck drug.
“Today’s authorization provides an additional treatment option against the COVID-19 virus in the form of a pill that can be taken orally. Molnupiravir is limited to situations where other FDA-authorized treatments for COVID-19 are inaccessible or are not clinically appropriate and will be a useful treatment option for some patients with COVID-19 at high risk of hospitalization or death,” said Patrizia Cavazzoni, M.D., director of the FDA’s Center for Drug Evaluation and Research in a December 23 statement. “As new variants of the virus continue to emerge, it is crucial to expand the country’s arsenal of COVID-19 therapies using emergency use authorization, while continuing to generate additional data on their safety and effectiveness.”
Ongoing research suggests that both antiviral medicines, which work by stopping the coronavirus from replicating, offer protection against Delta, Omicron, and other known variants. The Pfizer pill will likely be preferred over Merck's medication due to its greater efficacy and a lower risk for side effects.
What the latest data shows
In making its decisions, the FDA analyzed the results of Pfizer’s drug trial, which were released on December 14. The study of 2,246 adults at high risk for severe COVID-19 showed that the company’s antiviral pill, called Paxlovid, reduced the risk for hospitalization or death by 89 percent when given within three days of developing symptoms. The risk dropped 88 percent among those who took the drug five days after showing signs of infection. No deaths were reported.
A separate analysis of an ongoing study of adults who are not at high risk for severe disease showed the drug cut the risk for hospitalization and death by 70 percent.
Pfizer notes its antiviral drug resulted in a 10-fold drop in viral load after five days in both the high-risk group and the adults who did not have risk factors for severe disease. Pfizer added that lab data also indicates that its antiviral pill will help protect against Omicron and other known COVID variants.
Pfizer’s COVID pill is one of two authorized antiviral treatments. Merck’s oral COVID pill, called molnupiravir, was also shown to cut the risk for hospitalization and death from COVID-19.
On December 1, an advisory committee to the FDA narrowly agreed to recommend that the agency grant Merck emergency use authorization (EUA) for its experimental COVID-19 antiviral pill.
Like Pfizer’s drug, a five-day course of Merck’s oral medication could help fight the coronavirus soon after diagnosis and help prevent symptoms from developing or progressing. But the Antimicrobial Drugs Advisory Committee (AMDAC) had several concerns about the safety and efficacy of the drug.
During early clinical trials, the experimental antiviral pill cut the relative risk for hospitalization and death from COVID-19 in half. However, in a larger data analysis released November 26, the pill cut the risk by only about 30 percent compared to placebo.
The FDA committee was also cautious about its use among pregnant people. Animal studies showed the drug could pose serious risks to developing embryos and fetuses. Some experts also speculate that the drug could theoretically lead to more coronavirus variants due to how it works—creating a series of errors in the coronavirus’s RNA or genetic code.
The group’s final recommendation to the FDA was to set limits on when the Merck drug should be used and who would be able to receive it. The panel advised:
- The drug only be authorized for treatment within the first five days of symptoms.
- It would be for use among non-pregnant, non-hospitalized adults.
- Those who receive it would have mild to moderate symptoms but be at risk for severe COVID-19.
Similar to Pfizer, Merck’s data also suggests that its drug is effective against Delta and other concerning variants, including Gamma and Mu. Dr. Dean Y. Li, president of Merck Research Laboratories, says the drug will likely protect against Omicron as well.
“Importantly, we observed consistent efficacy among patients with more common variants at the time, and more recent preclinical evidence indicates that molnupiravir has antiviral activity against Omicron, which is encouraging considering the uncertain future of a rapidly evolving virus such as SARS-CoV-2,” said Li in a December 16 news release.
What happens now
If the CDC signs off on the FDA’s decisions, Pfizer and Merck’s antiviral pills could potentially be prescribed by healthcare providers (HCPs), allowing people to take the oral medications at home and reduce their risk for severe illness or hospitalization.
The move comes amid a renewed surge in new COVID cases amid the rapid rise of the Omicron variant, which now accounts for most new infections, according to the CDC. Community spread of the disease remains high across the United States and hospitalizations are on the rise.
The Merck and Pfizer COVID pills are additional tools doctors can use to manage COVID-19. As the pandemic enters its third year, total U.S. cases now stand at more than 50.7 million and the death toll has surpassed 803,000.
