An experimental coronavirus pill reduced the risk of hospitalization and death by 89% in high-risk people infected with the virus, pharmaceutical giant Pfizer announced Friday.
The effect of the drug, a five-day regimen designed to block the virus from making copies of itself, was found to be so strong midway through the study that an independent committee monitoring the clinical trial recommended it be stopped early. The data has not yet been published or peer-reviewed, but Pfizer said in a news release that it would submit the data to regulators “as soon as possible.”
Shares of Indianapolis-based Eli Lilly and Co., which makes an antibody treatment for COVID-19 that requires infusions, were down 2.7% in late-morning trading Friday, to $263.76 each.
Easy-to-deliver antiviral pills that blunt infections could be a powerful addition to the medical tool kit to manage the pandemic and equip the world for a future in which the coronavirus continues to circulate. Such treatments would augment the medical armamentarium, not replace highly protective vaccines, similar to how people receive flu shots but may be prescribed Tamiflu if they do fall ill.
“This is amazing news. My overall feeling was relief—it’s been a long path,” said Annaliesa Anderson, the chief scientific officer of Pfizer’s bacterial vaccines and hospital medicine division, who leads the program to develop the drug. Anderson, who has been working on the medicine since January 2020, said it was a “heart-in-your-mouth moment” when she learned the news Wednesday night while driving to Massachusetts for college visits with her daughter.
“We’re looking at end-to-end protection and treatment,” Anderson said. “We have the vaccine for protection, and now we have an opportunity for treatment.”
Pfizer has already begun manufacturing the drug and projects producing more than 180,000 pill packs by the end of this year. The company is working to rapidly scale up manufacturing to at least 21 million packs in the first half of next year, with a total production of 50 million packs in 2022. The company did not disclose the price.
The results mean the world could soon have two antiviral pills to treat people early in their sickness in addition to highly effective vaccines, if regulators deem the drugs safe and effective.
Drugmaker Merck announced a month ago that its antiviral pill, molnupiravir, cut the risk of hospitalization or death by half in high-risk patients. Regulators in Britain cleared molnupiravir for use this week in people who are diagnosed with covid-19, the disease caused by the virus, and have at least one risk factor for severe illness. In the United States, an expert advisory committee to the Food and Drug Administration is scheduled to meet to scrutinize Merck’s drug shortly after Thanksgiving—a crucial step before a drug is authorized for use. Merck has said it will produce 10 million treatment courses in 2021.
The work on Pfizer’s antiviral drug, called paxlovid, built off efforts by Pfizer scientists to develop treatments for the outbreak of severe acute respiratory syndrome (SARS) nearly two decades ago. Paxlovid combines a new molecule designed by Pfizer scientists in July 2020 and ritonavir, an antiviral drug used to treat HIV.
In a clinical trial, participants at high risk of developing severe illness were given the drug regimen—three pills a day, twice a day—within three days of their covid-19 symptoms beginning. Half received the experimental drug and half received a placebo. Paxlovid was 89 percent effective in reducing risk of hospitalization and death. Among 389 people who received the drug, three hospitalizations and no deaths were reported. Among 385 people who got a placebo, 27 hospitalizations were reported, with seven subsequent deaths.
The trial also included people who were given the drug within five days of symptom onset to test whether there was leeway on timing. The window of opportunity for giving antiviral drugs to thwart acute respiratory infections is short, so people must recognize their symptoms and get tested and receive results right away for drugs to be effective. Tamiflu, for example, is often given too late.
The drug also appeared to be effective even at five days after symptoms began. For about 600 people who received the drug within five days of symptoms, six people were hospitalized. Among the 600 who received a placebo, there were 41 hospitalizations and 10 subsequent deaths.
The company reported that side effects after treatment were similar between the group that received the drug and those that received the placebo, and were mostly mild.
Paxlovid blocks a coronavirus protease, an enzyme the virus needs to make copies of itself. It uses a different mechanism than the Merck drug, which disables the virus by garbling its genome and has raised concerns about its potential to cause mutations in people’s cells.
Public health experts have eagerly awaited the arrival of antiviral drugs—and some believe that in the long run, more than one will probably be necessary to create cocktails and combination therapies that ensure the coronavirus doesn’t find a way to escape.