FDA staff report says data shows Pfizer's Covid treatment Paxlovid is effective in high-risk adults

U.S. Food and Drug Administration staff on Tuesday said Pfizer's clinical trial results on its Covid antiviral pill Paxlovid support the drug's use in adults at high risk of progressing to severe disease. 

The FDA staff made the conclusion in briefing documents ahead of a meeting on Thursday, when external advisors on the agency's Antimicrobial Drugs Advisory Committee will discuss whether to recommend full approval of Paxlovid for the treatment of mild to moderate Covid in high-risk adults. 

At the meeting, advisers will consider evidence related to Paxlovid's efficacy, and vote on whether the benefits outweigh the risks of using the drug. The FDA typically follows the advice of its advisory committees but is not required to do so. 

The FDA authorized Paxlovid for emergency use in December 2021. Pfizer submitted an application for full approval of the drug in June 2022, and the FDA extended the review period of the application in December 2022. The agency is set to complete its review in May.

The meeting comes as companies like Pfizer and Moderna brace for a drop in sales of Covid vaccines and treatments that led to record revenues earlier in the pandemic. Sales of Paxlovid jumped to $18.9 billion in 2022, the first year it was available, but the company said it expects that revenue to drop 58% to $8 billion this year. 

More than 12 million courses of Paxlovid have been delivered to pharmacies across the U.S., according to federal data. Roughly 8 million Americans have taken the drug, with about 1.3 million doses available nationwide. 

The FDA staff reviewed Pfizer's mid-to-late stage clinical trials of Paxlovid. In one trial called EPIC-HR, Paxlovid showed an 86% reduction in the risk of hospitalization or death in high-risk adults who hadn't received a Covid vaccine. No deaths were observed in the trial.

Paxlovid has been plagued by reports of "rebound" Covid infections, where patients see their Covid symptoms or a positive test return after finishing a five-day course of the oral drug. Last year, both President Joe Biden and his former chief medical advisor Dr. Anthony Fauci experienced rebound cases after taking Paxlovid. 

But FDA staff highlighted trial data that showed overall rates of rebound ranged from 10% to 16%, "with no evidence of a higher rate of symptom rebound or moderate symptom rebound" in patients who received Paxlovid compared to a placebo. That was also regardless of patients' risk of severe disease, or whether Covid's omicron variant or an earlier strain was dominant, according to the staff.