Pfizer Announces Final Results for Oral Antiviral COVID-19 Candidate Paxlovid

Pfizer, Inc has announced final results from an analysis of its phase 2/3 EPIC-HR trial of its novel COVID-19 oral antiviral candidate nirmatrelvir (PF-07321332) tablets and ritonavir tablets (Paxlovid) confirming the drug’s efficacy.

The findings were consistent with the interim analysis announced in November 2021 showing that Paxlovid significantly reduced the risk of hospitalization or death for any cause by 89% compared with the placebo in non-hospitalized individuals who are high risk for COVID-19 when treated within 3 days of symptom onset.

“This news provides further corroboration that our oral antiviral candidate, if authorized or approved, could have a meaningful impact on the lives of many, as the data further support the efficacy of Paxlovid in reducing hospitalization and death and show a substantial decrease in viral load. This underscores the treatment candidate’s potential to save the lives of patients around the world,” Albert Bourla, chairman and CEO of Pfizer, said in a statement.

In the secondary endpoint, the study results show that the drug reduced the risk of hospitalization or death for any cause by 88% compared with the placebo in individuals treated within 5 days of symptom onset, an increase of 3 percentage points from the interim analysis.

The EPIC-HR data have been shared with the FDA as part of an ongoing rolling submission for emergency use authorization.

About 0.7% of individuals who received the study drug 3 days after onset of symptoms were hospitalized through day 28 following randomization compared with 6.5% of individuals who received the placebo and were hospitalized or died.

About 0.8% of individuals who received the study drug 5 days after the onset of symptoms were hospitalized or died through day 28 following randomization compared with 6.3% of individuals who received the placebo.

Relative risk reduction was 94% in individuals aged 65 years or older. In this group, about 1.1% of individuals who received the study drug were hospitalized through day 28 compared with 16.3% of individuals who received the placebo.

In the overall study population through day 28, no deaths were reported in individuals who received Paxlovid compared with 12 deaths in individuals who received the placebo.

In the EPIC-HR trial, in the secondary endpoint, SARS-CoV-2 viral load at baseline and day 5 have been evaluated for 499 individuals. After accounting for baseline viral load, geographic region, and serology status, Paxlovid reduced viral load by approximately 10-fold or 0.93 log10 copies/mL compared with the placebo, indicating robust activity against SARS-CoV-2, and representing the strongest viral load reduction reported to date for an oral COVID-19 agent.

Treatment-emergent adverse events (AEs) were compared between the study drug and the placebo, most of which were mild, at 23% and 24%, respectively.

Serious AEs, 1.6% for the study drug and 6.6% for the placebo, were observed, and the discontinuation of the study drug because of AEs were observed in individuals dosed with the study drug and the placebo at 2.1% and 4.2%, respectively.

“Emerging variants of concern, like Omicron, have exacerbated the need for accessible treatment options for those who contract the virus, and we are confident that, if authorized or approved, this potential treatment could be a critical tool to help quell the pandemic,” Bourla said.

Full study data are expected to be released later this month and submitted to a peer-reviewed publication.

Reference

Pfizer announces additional phase 2/3 study results confirming robust efficacy of novel COVID-19 oral antiviral treatment candidate in reducing risk of hospitalization or death. Pfizer. News release. December 14, 2021. Accessed December 14, 2021. https://www.pfizer.com/news/press-release/press-release-detail/pfizer-announces-additional-phase-23-study-results