Taking Pfizer’s bestselling COVID-19 pills,along with a rival’s treatment for the virus could be safe and more effective than either drug alone, federal scientists have found.
The combination could also offer a solution to what is known aswhen patients notice a return of symptoms after completing a course of Paxlovid.
But more research is needed, and the Food and Drug Administration does not currently allow doctors to prescribe both drugs to a patient.
The results, released this month as a preprint that has not yet been peer-reviewed, come from a study conducted by the National Institutes of Health on monkeys.
After being infected with the Delta variant, some received both Paxlovid and Lagevrio – the COVID-19 antiviral drug produced by Merck and Ridgeback Biotherapeutics.
Animals that received both treatments saw “decreased shedding and replication of SARS-CoV-2” early in their infection, and “milder disease” compared to those that received no only one drug or the other. The researchers found no concerning reactions in the animals given the two drugs.
However, the study authors cautioned that there are key questions that will need to be addressed in future trials and human experiments with the two drugs. And right now, the FDA says doctors aren’t allowed to prescribe Paxlovid to patients at the same time as Lagevrio.
Green-lighted last year as molnupiravir, Lagevrio is cleared by the FDA only for use in patients where alternative options “are not accessible or clinically appropriate.”
Lagevrio contains additional warnings that Paxlovid does not, such as the risks it could pose to reproduction – it should not be taken during pregnancy – and the possibility that it could lead to new worrying variants.
“Therefore, if a patient is taking Paxlovid, an FDA-cleared alternative COVID-19 treatment option, they would not be eligible for Lagevrio,” Chanapa Tantibanchachai, a spokesperson for the agency, said in a statement.
Another treatment option, Eli Lilly’s bebtelovimab, has the same kind of requirement, which effectively prevents suppliers from combining the monoclonal antibody with Pfizer’s pills.
‘No data’ on how to handle rebound
Earlier this year, South Korean researchers reported in a preprint that they found “profound” improvement in mice given the two drugs.
The NIH study tested both drugs in rhesus macaques, the “closest human substitute.”
But while the study authors speculated that the combination might “counteract the ‘rebound effect'”, the animals in their experiment received only four days of treatment before autopsies were performed.
In contrast, rebound cases in COVID patients have typically been reported a few days after the person has completed the full five-day course of Paxlovid.
In an email, Dr. Heinz Feldmann of the National Institutes of Health blamed the premature end of the study on “viral kinetics”: Before virus levels in animals dropped too low, scientists wanted to be able to compare viral load samples. in different parts of the body.
“We opted for maximum viral replication (day 3 or 4) to better show treatment efficacy,” Feldmann wrote.
The approach has sparked interest in part because the two drugs work in different ways. Paxlovid works by blocking the process by which the virus replicates in the body. Lagevrio aims to fight the virus by creating too many errors during its replication.
“Combination antivirals are the rule in other viral diseases, for example HIV and hepatitis C. Combining antivirals can increase potency and decrease the risk of emergence of resistant viruses,” said Dr Roy Gulick, chief of the division of infectious diseases. at Weill Cornell Medicine, said in an email.
Gulick is co-chair of the NIH’s COVID-19 Treatment Guidelines Group, which has continued to issue updated recommendations for physicians treating patients throughout the pandemic.
He also pointed to other viruses that don’t need more of an antiviral, such as herpes and hepatitis B.
“This is potentially worth studying in humans, but it may be difficult to improve on Paxlovid’s 89% success rate,” Gulick wrote, citing Pfizer’s early results in unvaccinated adults at high risk.
In August, the FDA announced it would change Pfizer’s emergency use authorization to require a clinical trial to investigate cases of rebound. The company says it plans to study “retreating” with another course of Paxlovid for these patients.
So far, the NIH panel’s recommendations to physicians treating rebound cases state that there are “currently no data on the effectiveness of administering longer courses or a second course of boosted nirmatrelvir to ritonavir”.
that of the president is among Americans who said they battled a COVID rebound.
The 81-year-old told the NIH Record that he sought a second course of the pills, after feeling the return of symptoms.
“I got much sicker than the first time,” Fauci said.
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