Pfizer’s Paxlovid study doesn’t answer key questions about benefits for broader populations

Pfizer said on Tuesday that a closely followed study of its antiviral Paxlovid in patients with Covid but who do not have risk factors for severe disease showed no benefit in accelerating the improvement of Covid symptoms. , but seemed to prevent doctor visits and hospitalizations.

Also, due to the small number of hospitalizations in the study as a whole, it did not produce a statistically significant result indicating whether patients who had already been vaccinated against Covid were hospitalized less often if they received Paxlovid. .

The data in no way invalidates previous findings that show Paxlovid prevents hospitalizations and saves lives in patients at high risk of severe Covid. But the results, published in a press release, may take time to be assimilated and understood by the experts.

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“I think this is one where you have to say it’s hard to draw conclusions based on a press release, but this data looks intriguing but not compelling,” said Andy Pavia, division chief. of Pediatric Infectious Diseases at the University of Utah Hospital.

The results are likely to spark debate about how cautiously doctors should prescribe Paxlovid. Pfizer’s first profound results came from a group of unvaccinated high-risk patients. But the Food and Drug Administration has cleared it for anyone with at least one risk factor such as diabetes or high blood pressure; anecdotally, doctors report that the drug is widely used in high-risk vaccinated patients, especially amid heavy pressure from the US government to ensure the drug reaches everyone indicated to get it.

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Still, there was little data on the drug’s effectiveness in these high-risk vaccinated patients and open questions about whether it might also be helpful in patients who don’t have any risk factors.

“This reinforces the fact that Paxlovid won’t have a big role in vaccinated people, except in people who may be most at risk,” said Walid Gellad, director of the Center for Pharmaceutical Policy and Prescription. University of Pittsburgh. “Maybe in a larger trial it would be statistically significant, but the effect is small.”

In a statement, Pfizer CEO Albert Bourla said: “With up to 40-50% of people globally deemed to be at high risk, we believe there remains a significant unmet need for treatment options. to help fight this disease, and we will continue to prioritize efforts to advance the development of Paxlovid.

But Gellad argued that the data suggests finding the subset of patients most at risk is crucial, especially since the drug comes with side effects and low rebound potential.

“We really need to understand who is really at high risk and we need to know who is hospitalized,” he said.

Real-world studies in widely – but not fully – vaccinated populations in Hong Kong and Israel have also suggested that Paxlovid offers some benefit to low-risk patients, with a recent Israeli study finding the drug reduced the risk of serious illness or death by 46% in patients. covered by the largest local healthcare provider.

The Israeli study suggested that the drug had the greatest benefit for patients with neurological disease, malignancy, or taking immunosuppressive drugs.

Real-world studies in widely – but not fully – vaccinated populations in Hong Kong and Israel have also suggested that Paxlovid offers some benefit for low-risk patients, with a recent Israeli study finding that the drug reduced the risk of hospitalization by 46% in patients covered by the largest local healthcare provider.

The Israeli study suggested that the drug had the greatest benefit for patients with neurological disease, malignancy, or taking immunosuppressive drugs.

Pfizer announced in December that an initial review of the study did not appear likely to achieve its primary goal of showing relief from Covid symptoms at four days, but patients who received Paxlovid appeared less likely to have needed medical attention than those who received a placebo.

In an updated analysis of 1,153 patients enrolled in the study through December 2021, there was a 51% difference in the need for medical care – that’s five patients who needed it in the treatment arm, versus 10 on placebo – but the result was not statistically significant.

The results were similar, however, in patients who had previously been vaccinated. The study originally included volunteers who were fully vaccinated but were at high risk for Covid symptoms. After Paxlovid cleared these people, they could no longer be enrolled in the study. Pfizer has changed the entry criteria to include people whose last vaccination was at least 12 months prior to enrollment.

A subgroup analysis of 721 vaccinated adults with at least one risk factor for progression to severe Covid indicated that those who received Paxlovid were 57% less likely to be hospitalized or die, but the result did not was not statistically significant. Three patients were hospitalized or died in the Paxlovid group versus seven in the placebo group.

Davey Smith, an infectious disease expert at the University of California, San Diego, said he viewed the data as supporting giving Paxlovid to those who have been vaccinated and caught Covid and who have at least one high risk factor.

“It answers an open question for some time: whether or not vaccinated people with high-risk diseases should be treated. Myself and other doctors have done it. But it’s good to have a some insurance.

Even without statistical significance, he said, “I think it’s going in the right direction.”

Pavia said a big question about whether people at low risk should receive Paxlovid won’t be the results of the study, but whether or not strains of the SARS-CoV-2 virus develop resistance to the drug. drug as it becomes more widely used. If little resistance develops, doctors can use the drug widely. But if there’s a risk of resistance, they’ll probably keep it in reserve for higher-risk patients.


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