Pfizer's experimental COVID-19 pill dramatically reduced hospitalization and death in a large study of adults at high risk of severe coronavirus disease, a major finding that brings closer a convenient and potent treatment for people who are unvaccinated or still at risk.
In a Friday statement, the drugmaker said trial investigators reported that treatment with the pill, called Paxlovid, led to an 89% reduction in risk versus placebo for patients who received it within three days of symptoms. The high degree of effectiveness prompted Pfizer, after discussions with Food and Drug Administration officials, to end the trial early and speed up plans to ask the agency for an emergency authorization.
An application, if submitted as planned, would come close on the heels of another request from Merck & Co. and Ridgeback Biotherapeutics, which could soon receive FDA authorization for their oral drug molnupiravir. On Thursday, the British government granted molnupiravir regulatory clearance, making it the first pill available to treat COVID-19.
The 89% risk reduction reported by Pfizer with Paxlovid surpasses the 50% benefit observed in a late-stage clinical trial testing Merck and Ridgeback's pill in a similar patient population. While comparing across trials can mislead, the results from Pfizer suggest another powerful coronavirus antiviral is within reach. Investors took notice, sending Pfizer shares surging 10% higher in morning trading, while Merck's fell by 9%.
The positive findings for both drugs could lead to governments around the world stockpiling supply and, for their makers, blockbuster sales. Merck recently forecast between $5 and $7 billion in sales of molnupiravir, to be sold as Legevrio, through the end of 2022. But Paxlovid's seemingly superior efficacy could make it a strong alternative option.
Paxlovid's benefit also appears higher than the synthetic antibody drugs developed by Regeneron and Eli Lilly, which reduced the risk of hospitalization or death by around 70%.
Announcement of the trial results for Paxlovid came at the end of a week in which the first young children received Pfizer's coronavirus vaccine after it was authorized for pediatric use by the FDA last week. Pfizer also increased its forecast for sales of its vaccine this year to $36 billion, a historic sum for a pharmaceutical product and one equivalent to roughly 80% of sales from the rest of Pfizer's business.
"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. "These data suggest that our oral antiviral candidate, if approved or authorized by regulatory authorities, has the potential to save patients' lives, reduce the severity of COVID-19 infections, and eliminate up to nine out of 10 hospitalizations."
Brian Abrahams, an analyst at RBC Capital Markets, wrote in a note to clients that the Paxlovid results "caps [a] transformative week in COVID-19 mitigation" that "should accelerate our return towards our pre-COVID normalcy."
The study, called EPIC-HR, enrolled unvaccinated people with confirmed coronavirus infections and at least one condition associated with increased risk of severe COVID-19. Patients were randomized to receive either a placebo or Paxlovid along with the HIV antiviral ritonavir, which Pfizer said helps slow the body's metabolism of Paxlovid.
Results came from an interim analysis performed after 1,219 patients had enrolled and completed 28 days of follow-up. Among the 389 patients who received the Paxlovid-ritonavir combination within three days of symptom onset, three were hospitalized and none died, compared to 27 hospitalizations among the 385 people who received a placebo, seven of whom later died.
Measuring efficacy in a large group of participants who received Pfizer's drug within five days of symptoms beginning, the risk reduction versus placebo was slightly lower, at 85%. Six of 607 patients given the Paxlovid-ritonavir combination were hospitalized and none died, while 41 of the 612 patients who received the placebo were hospitalized with 10 dying.
Pfizer's data also boosted the fortunes of Enanta Pharmaceuticals, which is developing a COVID-19 antiviral that works in a similar fashion as Paxlovid. Shares in the biotech rose 13%, although Abrahams noted that Paxlovid's high efficacy may leave little room for improvement from a follow-up drug.
Japanese biotech Shionogi is also developing a similar type of antiviral known as a protease inhibitor.
Should Paxlovid win emergency authorization, Pfizer may have capacity to manufacture up to 50 million doses, Umer Raffat, an analyst at Evercore ISI, wrote in a note to clients.
Pfizer is also testing Paxlovid in patients who are not at high risk of severe COVID-19, including some vaccinated individuals, and as a preventive therapy for people who aren't infected but get exposed to the virus by a member of their household. The company expects those trials to deliver results early next year.