Advisers to the US Food and Drug Administration voted 16-1 on Thursday in support of full approval of Paxlovid, stating that the benefits outweigh the risks of the drug for treatment of mild to moderate Covid-19 in adults who are at high risk for severe disease, including hospitalization and death.
Before the antiviral medication is fully approved, the FDA -- which typically follows the recommendations of its independent advisory committee -- must conduct its own review. That's expected to wrap up in May.
More than 8 million people in the US have received Paxlovid, a combination of the drugs nirmatrelvir and ritonavir, since it became available under emergency use authorization in December 2021.
"I'd say besides oxygen, Paxlovid has probably been the single most important tool in this epidemic, and it continues to be," said Dr. Richard Murphy, chief of infectious diseases with the Veterans Affairs White River Junction Medical Center and a member of the FDA's Antimicrobial Drugs Advisory Committee, who voted in support of approval at the meeting.
"We still have many groups that stand to benefit from the use of Paxlovid, including unvaccinated persons, undervaccinated persons, elderly, immunocompromised, and the other treatment options that we have have significant disadvantages," he said.
A study published Friday in the medical journal JAMA Health Forum estimated that if Paxlovid uptake during the winter Omicron wave had been what it is now, nearly 5,000 deaths would have been prevented.
Data from phase 2 and 3 clinical trials supports the efficacy of Paxlovid regardless of Covid vaccination status or prior infection, the FDA said in documents released ahead of Thursday's meeting. The agency also said it is reasonable to conclude, despite limited data, that Paxlovid is "likely to retain clinical efficacy" in high-risk adults with Covid infection caused by the Omicron variant of the coronavirus, as with earlier variants.
"I thought that the efficacy data were clear and convincing," said Dr. Shankar Swaminathan, chief of infectious diseases at the University of Utah School of Medicine, who voted in support of approval Thursday. "I think that the fact that the drug has retained activity against various evolutionary strains of the virus is also reassuring and gives hope that this will continue to be the case going forward."
Not linked to Covid rebound
The FDA also concluded that Paxlovid is not associated with Covid-19 rebound, in which people test positive or see their symptoms return after they finish the five-day course of the drug.
The agency said it has reviewed data regarding rebound cases, which some users have reported since Paxlovid was authorized in 2021. Last year, both President Joe Biden and his former chief medical adviser, Dr. Anthony Fauci, reported rebound symptoms after taking Paxlovid.
However, based on clinical trial data, the FDA "did not identify a clear association between Paxlovid treatment and Covid-19 rebound."
Covid rebound rates ranged from 10% to 16%, with no difference between people who took Paxlovid and those who took a placebo. This was also regardless of a person's risk of severe disease with the Omicron variant compared with the Delta variant, according to clinical trial data reviewed by the FDA.
Overall, the agency said, the findings indicate that Covid-19 rebound may occur in a subset of infections as part of the natural progression and resolution of the disease.
Monitoring drug-drug interactions
No major safety concerns were identified in the clinical trial data, the FDA said. However, the agency has flagged 137 medications with Paxlovid drug-drug interactions (DDIs) that may lead to serious adverse reactions.
Paxlovid may keep the body from metabolizing certain drugs, leading to higher drug concentrations that can lead to serious or life-threatening reactions, according to an FDA Emergency Use Authorization Fact Sheet. Drugs that should not be taken with Paxlovid include some medications to treat conditions such as high cholesterol, gout, migraine, irregular heartbeat and benign prostatic hyperplasia.
According to the agency, more than 50% of Paxlovid-eligible patients may be on medication with a DDI at the time of Covid diagnosis.
"I would just emphasize that we underscore the importance of risk-mitigation to the prescriber, primary care physicians and other prescribers in terms of drug-drug interactions," said FDA committee member Dr. David Hardy, an adjunct clinical professor at the Keck School of Medicine at the University of Southern California, who voted in support of approval. "That's where I think we may get into trouble -- or I can say where they can get into trouble -- prescribing this medication without a good knowledge of what ritonavir does to other medications."
The committee said the benefits of Paxlovid may not outweigh the risk of adverse drug reactions in all patients. For those at high risk of severe Covid-19, DDIs can be managed by holding the drug, adjusting the dose or increasing monitoring.
Clinical trials on the safety and efficacy of Paxlovid in children, people who are pregnant and those with weakened immune systems are ongoing.
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