Pfizer study results show Paxlovid benefit less clear in lower-risk patients

Dive Brief:

• Mixed results from a large study of Pfizer’s COVID-19 pill Paxlovid signal the antiviral drug’s benefit is not as clear-cut in lower-risk or vaccinated adults, although treatment still appears to lessen the need for medical care.
• In a trial of over 1,100 adults, Paxlovid reduced the relative risk of hospitalization or death versus placebo by 51%, but the difference between groups was not statistically significant, Pfizer said in a press release Tuesday. The company previously disclosed the study had missed its main goal of showing Paxlovid could more effectively ease symptoms compared to placebo.
• Among vaccinated adults with at least one risk factor for severe COVID-19, Paxlovid lowered the risk of hospitalization or death by 57%, but that effect also was not significant. In both groups, however, there were few cases of either outcome and, as a result, Pfizer plans to halt further enrollment into the study.

Dive Insight:

Since Paxlovid’s authorization in December, the drug has become a go-to treatment in the U.S., with more than 1.1 million courses administered through early June. The spread of omicron, meanwhile, has forced regulators to shelve antibody drugs from Eli Lilly and Regeneron that were relied on earlier in the pandemic but aren’t effective versus the variant.

Paxlovid is cleared only for adults and children older than 12 years who are at high risk of severe COVID-19, even though anecdotally it appears to have been prescribed more widely as supplies increased and the Biden administration pushed its use.

Pfizer’s study, called EPIC-SR, was meant to find out how well the treatment worked in a broader population, including “standard-risk” adults and those who are vaccinated. (The initial study of Paxlovid that showed dramatic 90% efficacy in preventing COVID-19 hospitalization and death was in unvaccinated adults.)

The results disclosed by Pfizer Tuesday don’t provide definitive answers, however. While Paxlovid seemed to lessen the relative risk of hospitalization and death, the difference between treated and placebo groups wasn’t large enough for investigators to conclude Paxlovid was superior.

Among the 1,153 participants included in Pfizer’s overall analysis, there were only 15 cases of hospitalization or death: 5 among Paxlovid-treated patients and 10 among those given placebo. The company previously reported in December a nominal 70% risk reduction based on results from roughly 57% of the total number of patients who were eventually enrolled.

Paxlovid did result in a 62% decline in the number of COVID-19 medical visits versus placebo, as well as a 72% reduction in the number of days spent in the hospital between Paxlovid-treated patients who were hospitalized and those who had received placebo. As the study missed its main goals, the statistical comparison on both measures was considered descriptive, or nominal.

Pfizer described the data as supportive of Paxlovid’s use, noting the large number of people worldwide who are considered to be at high risk.

The company will include the EPIC-SR results in its planned submission to the FDA for full approval of Paxlovid in high-risk individuals. Pfizer also said it maintains its forecast for Paxlovid sales this year, which it previously projected will be at least $22 billion.

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