Pfizer Inc. issued a statement last week, saying it will cease enrollment” of “standard-risk” participants in clinical trials for its COVID-19 antiviral pill, Paxlovid.
The move comes after the company’s trial results demonstrated that the drug had a negligible effect in reducing hospitalizations or fatalities for that category of test subjects.
Results also indicated a negligible effect on people with “at least one risk factor for severe COVID-19,” but Pfizer plans on conducting further trials on that population group.
Pfizer stated it will “focus efforts on generating further data on Paxlovid in vulnerable populations, including durations in treatment for immunocompromised individuals as well as exploring other clinical development opportunities, such as its potential use in hospitalized patients with mild diseases.”
Paxlovid consists of two antiviral drugs: NirmatElvir and Ritonavir. The Food and Drug Administration (FDA) authorized it for emergency use to treat COVID-19 in December 2021, meaning healthcare providers could administer the drug to patients before efficacy trials had concluded.
More than 65 countries worldwide have used Paxlovid on an emergency basis to treat the disease.
Pfizer began the trials in August 2021, comparing Paxlovid against a placebo. The “standard-risk” subject sample consisted of un-hospitalized, symptomatic adults with COVID-19 who were “at low risk of progressing to severe illness.”
At the conclusion of the study in December, Pfizer stated that Paxlovid failed to generate “self-reported, sustained alleviation of all symptoms for four consecutive days, as compared to placebo.”
The initial trial results saw only a small sample of both the test and control groups resulting in hospitalization — three and 10, respectively, out of a total of 854 test subjects.
In its statement last Tuesday, Pfizer revised its numbers from the trial after finding that five subjects who received Paxlovid ended up hospitalized rather than three. The control group data did not change.
According to the company, the difference between hospitalization rates in the test and control groups was “statistically insignificant,” and therefore did not justify continued trials on “standard-risk” participants.
While Paxlovid may not prove effective for adults with a “standard risk” of developing severe disease, Pfizer CEO Albert Bourla seemed undeterred in defending the drug’s efficacy.
He was quoted in the statement claiming broader trials “support the efficacy and safety profile for PAXLOVID in the treatment of mild-to-moderate COVID-19 patients with at least one risk factor for progressing to severe COVID-19, regardless of vaccination status.”