Pfizer COVID-19 Antiviral Pill Significantly Reduces Hospitalizations, Death

Investigative protease inhibitor antiviral pill of combination PF-07321332 and ritonavir (PAXLOVID) is associated with a nearly 90% reduction in risk of hospitalization and/or death at 28 days among patients with COVID-19, according to new unpublished interim data shared by Pfizer.

In a press release announcing to-be-published data from the phase 2/3 Evaluation of Protease Inhibition for COVID-19 in High-Risk Patients (EPIC-HR) trial, Pfizer shared findings suggesting their oral antiviral therapy may provide significant risk reduction against composite endpoints of severe COVID-19 progression in patients at greater risk of developing worse forms of COVID-19.

The findings come 1 day after the UK marketing authorization for Merck’s molnupiravir, which in similar late-phase trial data showed a 50% reduction in risk of hospitalization or death versus placebo in patients with COVID-19. Investigators and experts have been vying for opportunities to alleviate hospital and intensive care spacing and resources dedicated to severe COVID-19; the addition of effective oral medication to reduce the risk of patient progression to severe disease could both save lives and benefit overwhelmed hospital systems in the US.

EPIC-HR Trial Data

The EPIC-HR trial, which began enrollment in July, is a randomized, double-blind assessment of PAXLOVID in adults with COVID-19 who are currently not hospitalized, but have been deemed at high risk of severe illness progression based on clinical characteristics. The interim data’s primary analysis included 1219 adults who were enrolled in the study by September 29; enrollment is ongoing across all inhabited continents except Australia.

Eligible patients had a laboratory-confirmed SARS-CoV-2 infection within 5 days of enrollment, as well as mild to moderate symptoms. Similar to the ongoing molunpiravir assessment, patients were required to have ≥1 characteristic or underlying medical condition associated with increased risk of developing severe COVID-19 illness.

Investigators sought a primary outcome of death or hospitalizations after 28 days post-randomization to either PAXLOVID or placebo.

Among patients treated within 3 days of COVID-19 symptom onset, investigators observed an 89% reduction in risk of disease-related hospitalization or death with PAXLOVID: 3 patients (0.8%) treated with the investigative pill were hospitalized through 28 days, versus 27 patients (7.0%) treated with placebo who were either hospitalized or died (P <.0001).

Investigators additionally observed significant reductions among patients treated within 5 days of COVID-19 symptom onset; just 6 patients on PAXLOVID were hospitalized and none died (1.0%), versus 41 patients on placebo who were hospitalized and 10 who died (6.7%; P <.0001).

A safety data review was additionally conducted including 1881 EPIC-HR patients with data available at the interim analysis. Patients treated with PAXLOVID had slightly fewer treatment-emergent adverse events (19%) than those given placebo (21%); a majority of events were mild in severity. Treatment discontinuation due to adverse events occurred in 2.1% of patients administered PAXLOVID.

Next Steps for PAXLOVID

Pfizer has planned to cease enrollment of EPIC-HR on the basis of the significant efficacy findings and will submit the data as part of the rolling submission to the US Food and Drug Administration (FDA) for emergency use authorization (EUA) of PAXLOVID for the treatment of COVID-19. According to the company, such plans were recommended in consultation with the FDA and an independent data monitoring committee.

The antiviral pill could become the first of its kind granted authorization for the treatment of COVID-19—and the first available oral therapy that functions as a SARS-CoV-2-3CL protease inhibitor. Pfizer hopes its role is served in at-home therapy for reducing illness, severity, and transmission risk of COVID-19, pending FDA decision.

In the meantime, Albert Bourla, chairman and chief executive officer of Pfizer, called the new interim data for PAXLOVID a “real game-changer” in the fight against COVID-19.

“These data suggest that our oral antiviral candidate, if approved or authorized by regulatory authorities, has the potential to save patients’ lives, reduce the severity of COVID-19 infections, and eliminate up to nine out of ten hospitalizations,” Bourla said.