The company hopes it can eventually offer the pill, given in combination with an older antiviral drug called ritonavir, to people to take at home before they get sick enough to go to the hospital.
A so-called interim analysis — done before the trial was scheduled to end — showed an 89% reduction in the risk of hospitalization or death from Covid-19 if patients got it soon enough, the company said.
The results were so striking, the company stopped the trial and is preparing to make its case to the US Food and Drug Administration for emergency authorization of the drug.
“Today’s news is a real game-changer in the global efforts to halt the devastation of this pandemic,” Pfizer CEO Albert Bourla said in a statement.
Pfizer released the results in a news release and did not provide scientists to discuss the data ahead of release. The data has not been peer reviewed or published. The company says it will share more specifics in a peer-reviewed paper and in its submission to the FDA.
The company has been testing the drug in adults with Covid-19 who are considered at high risk of progressing to severe illness. The volunteers have been randomly given either the pill combination or a placebo within three days or five days of their symptoms starting.
The pill, called Paxlovid and also known by the experimental name PF-07321332, is what’s known as a protease inhibitor. It’s designed to stop the virus from multiplying. Giving it along with ritonavir slows its breakdown in the body, the company said.
Pfizer said 0.8% of patients who got the drug combination within three days were hospitalized within four weeks — three out of 389 patients — compared to 7% of patients who got placebos, or 27 out of 385. And seven of those who got placebos died, Pfizer said. No one who got the treatment died within a month.