The most popular COVID-19 antiviral is Paxlovid (nirmatrelvir [PF-07321332] and ritonavir). The manufacturer of the drug, Pfizer Inc. (NYSE: PFE), anticipates selling about $22 billion worth of Paxlovid this year.
Complicating matters, however, is the failure of the drug to meet its primary endpoint of self-reported, sustained alleviation of all COVID-19 symptoms for four consecutive days in the EPIC-SR study.
In a press release describing the gathering of new data to support a new drug application submission, Pfizer noted that EPIC-SR data from standard-risk vaccinated and unvaccinated patients were not statistically significant but underscored its efficacy overall.
In the EPIC-SR study, the drug passed the statistically significant threshold of reducing COVID-19-related medical visits per day compared to placebo by 62%. In addition, the study found a non-significant 70% relative risk reduction for the key secondary endpoint of hospitalization or death.
The latest data “appear to be intriguing but not convincing,” Dr. Andy Pavia of the University of Utah Hospital recently told STAT.
Paxlovid has also received attention for its association with rebounding COVID-19 infections. Recent research published in Clinical Infectious Diseases indicates that such rebounds are rare. Only 0.8% of patients featured in the study had such a rebound.
Another complication is that Pfizer halted enrollment for the EPIC-SR study owing to the low rate of hospitalization or death in the standard-risk population.
Paxlovid is currently authorized Paxlovid for individuals at least 12 years of age with mild-to-moderate COVID-19 who are at risk for progression to severe COVID-19.
It may be difficult for the drug to find use for individuals without an elevated risk of severe COVID-19. “Results from our Phase 2/3 EPIC-HR and EPIC-SR studies, as well as post-authorization experience, 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,” said Dr. Albert Bourla, Pfizer CEO, in a statement. “With up to 40-50% of people around the world estimated to be high risk, we believe there remains a significant unmet need for treatment options to help combat this disease, and we will continue to prioritize efforts to advance the development of PAXLOVID.”
PFE shares were mostly flat, falling a penny to $47.92.