Pfizer’s Covid-19 Pill Failed Study Testing Its Preventive Use

Paxlovid, authorized to treat high-risk people early in infection, didn’t meaningfully reduce illness in exposed adults

Authors: Jared S. Hopkins Apr. 29, 2022 The Wall Street Journal

The Covid-19 pill from Pfizer Inc. failed to prevent symptomatic infections in adults who had been exposed to the pandemic virus, a late-stage study found.

Pfizer said Friday that the drug, named Paxlovid, failed the study’s main objective of meaningfully reducing the risk of confirmed and symptomatic Covid-19 infections in adults who were exposed to the virus by someone in their household.

Paxlovid was cleared for use in December by U.S. health regulators to treat people 12 years and older early in the course of their disease who are at high risk of developing severe Covid-19.

The treatment consists of two components, nirmatrelvir and a widely used generic antiviral, and is taken twice daily for five days.

The pill’s key advantage over other Covid-19 treatments has been that it can be taken at home to avoid hospitalization. Another antiviral pill, from Merck & Co. and Ridgeback Biotherapeutics LP, has also been cleared for use.

Paxlovid’s authorization was based on a late-stage study finding the pill was highly effective at safely cutting the risk of hospitalization or death when taken within five days of symptoms.

Pfizer has also been studying the drug for other uses, including whether it could prevent disease.

In a 2,957-subject trial testing whether Paxlovid could also work preventively, researchers found that the risk of developing an infection declined by 32% in subjects who received Paxlovid for five days compared with people who got a placebo, and declined 37% in people who received treatment for 10 days, Pfizer said.

The results weren’t statistically significant and failed the study’s primary endpoint, Pfizer said.

“While we are disappointed in the outcome of this particular study, these results do not impact the strong efficacy and safety data we’ve observed in our earlier trial for the treatment of Covid-19 patients at high risk of developing severe illness, and we are pleased to see the growing global use of Paxlovid in that population,” Pfizer Chief Executive Albert Bourla said.

Researchers didn’t observe any serious safety concerns and the safety profile was consistent with previous Paxlovid studies, Pfizer said.

Pfizer continues to study Paxlovid in patients who are at low risk of developing severe disease to see if it can reduce the risk of hospitalization and death.

An interim analysis last year found the drug failed to reach the trial’s goal of resolving or reducing symptoms among the people who took the pill within four days of infection. Results are expected as early as the third quarter, according to a company spokesman.

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