FDA advisers endorse benefits of Paxlovid as a covid treatment

An expert advisory panel from the Food and Drug Administration (FDA) on Thursday endorsed Paxlovid as a treatment for adults with COVID who are at high risk of progression to severe disease. The move is likely to lead to full approval of the drug, which has been available under emergency use authorization.

The 16-1 vote came after the agency released new analysis showing that Paxlovid reduced hospitalizations and deaths among vaccinated and unvaccinated people. The agency’s researchers estimated, based on January covid rates, that Paxlovid could “save 1,500 lives and avert 13,000 hospitalizations each week in the United States.”

“I would say that, other than oxygen, Paxlovid has probably been the most important treatment tool in this epidemic and continues to be so,” said Dr. Richard A. Murphy, chief of infectious diseases at White River Junction VA Medical Center. in Vermont, he said explaining his vote in favor of the treatment.

Consumers have been particularly concerned by reports that people taking the drug experience a Covid “rebound”, in which symptoms return a few days after they clear up. The FDA’s analysis found evidence of rebound among patients who received the treatment, but the data also showed that some covid patients who did not receive Paxlovid also experienced rebound.

The agency concluded that there was no significant difference in rebound rates between the two groups and that rebound had no impact on the risk of developing serious illness. At Thursday’s expert meeting, FDA researcher Dr. Stephanie Troy suggested that covid rebound “may be a natural part of the clinical course of covid-19 in a small subset of patients,” whether they take Paxlovid or not.

Currently, only one antiviral drug, remdesivir, has full FDA approval as a covid treatment. Its use is limited, because patients have to go to a clinic to receive infusions three days in a row. Paxlovid, a pill, can be taken at home for five days.

Representatives for Pfizer, the maker of Paxlovid, said Thursday that the company was continuing to study the drug in immunocompromised or pregnant patients, as well as for the prevention of prolonged Covid.

Another pill, molnupiravir, also has emergency use authorization as a Covid treatment. But concerns have been raised about its safety, prompting regulators in Europe to advise against its approval there.

In Japan, another antiviral pill, called Xocova, has emergency approval. The drug is in a clinical trial in the United States.

The FDA granted emergency use authorization for Paxlovid in December 2021 based on preliminary data from a clinical trial. In that trial, unvaccinated people who were at high risk of severe Covid — people older than 60 or with conditions like diabetes — saw an 88 percent reduction in their risk of hospitalization.

Pfizer has continued that trial and others. In one study, participants were either vaccinated and at high risk, or unvaccinated and at low risk. In the latest analysis, Paxlovid reduced hospitalization and death by 86 percent in unvaccinated high-risk subjects.

Among high-risk people who were vaccinated, the reduction was 58 percent. People who gained immunity from a previous infection also saw a reduced risk after taking Paxlovid.

The rebound phenomenon drew attention after such famous patients as President Biden and Dr. Anthony Fauci took the drug, tested negative for Covid, and then days later tested positive again.

The FDA found that a small fraction of people who took Paxlovid experienced a rebound, just like those who took a placebo. In one trial, they estimated that 8.3% of people who took Paxlovid tested positive after an initial negative test, compared to 5.7% of patients who received a placebo.

However, the rebound seen among those taking Paxlovid was not associated with longer illness or worsening symptoms.

“It’s nice to know that this phenomenon exists, but the data shows us that, in a real-life clinical sense, it doesn’t have much of an impact on patients,” said Dr. Adi Shah, an infectious disease specialist at the Mayo Clinic who it was not on the review panel.

Since December 2021, when Paxlovid received emergency use authorization, federal officials have delivered more than 12.5 million doses nationwide. At the advisers’ meeting, Pfizer officials said 10 million doses had been taken in the United States and 14 million worldwide.

However, acceptance has been more slow than expected. One concern is related to interactions between medications that older adults often take. He FDA analysis looked into that problem, too.

Agency researchers found that a “significant” proportion of patients who are eligible for Paxlovid also take medications, either to lower bad cholesterol or treat high blood pressure, which can cause interactions. In total, the FDA has received 147 reports of hospitalizations and six deaths following drug interactions with Paxlovid.

“Drug interactions are a major concern” that requires continued attention, said Dr. Lindsey Baden of Harvard Medical School and chair of the expert committee.

Apoorva Mandavilli contributed reporting.