Pfizer’s COVID-19 Oral Antiviral Cuts Hospitalization and Death By 89%

November 5th, 2021 – Just a month since Merck’s game-changing results for Molnupiravir, a broad-spectrum antiviral against COVID-19, now it’s Pfizer’s turn. Given the global impact of the pandemic, Pfizer didn’t just stop with its COVID-19 vaccine. The pharma giant continued to strengthen its anti-COVID-19 armamentarium with its investigational oral antiviral candidate PAXLOVID (PF-07321332, ritonavir).

Today, the company announced that PAXLOVID was found to significantly reduce hospitalization and death by 89% after an interim analysis of the Phase 2/3 EPIC-HR study. If approved, PAXLOVID would be the first oral antiviral of its kind, a specifically designed SARS-CoV-2-3CL protease inhibitor.

Albert Bourla, Chairman and CEO of Pfizer, believes this news is a real game-changer in the global efforts to halt the devastation of this pandemic. He strongly feels once approved or authorized by regulatory authorities, Pfizer’s oral antiviral candidate has the potential to save patients’ lives, reduce the severity of COVID-19 infections, and eliminate up to nine out of ten hospitalizations.

“Pfizer is incredibly proud of its scientists, who designed and developed this molecule, working with the utmost urgency to help lessen the impact of this devastating disease on patients and their communities. He expressed a deep sense of gratitude to all the patients, investigators, and sites around the world who participated in this clinical trial with a common goal of bringing forth a breakthrough oral therapy to help combat COVID-19,” said Mikael Dolsten, MD, Ph.D., CSO and President, Worldwide Research, Development and Medical of Pfizer.

PAXLOVID and the EPIC Development Program

PAXLOVID is an investigational SARS-CoV-2 protease inhibitor antiviral therapy designed to block the activity of the SARS-CoV-2-3CL protease, an enzyme that the coronavirus needs to replicate.

It inhibits viral replication at a stage known as proteolysis, which occurs before viral RNA replication. It can be prescribed at the first sign of infection or at first awareness of exposure, potentially helping patients avoid severe illness, which can lead to hospitalization and death.

Pfizer initiated the EPIC-HR (Evaluation of Protease Inhibition for COVID-19 in High-Risk Patients) study in July 2021 following positive Phase 1 clinical trial results. Phase2/3 EPIC-HR is a randomized, double-blind study of non-hospitalized adult patients with COVID-19, who are at high risk of progressing to severe illness.

The Phase 2/3 EPIC-SR (Evaluation of Protease Inhibition for COVID-19 in Standard-Risk Patients) and EPIC-PEP (Evaluation of Protease Inhibition for COVID-19 in Post-Exposure Prophylaxis) studies, which began in August and September 2021, respectively, were not included in this interim analysis and are ongoing.

Interim Analysis 

The primary analysis evaluated data from 1219 adults who were enrolled by September 29, 2021, from clinical trial sites across North and South America, Europe, Africa, and Asia, with 45% of patients located in the United States.

Enrolled individuals had a laboratory-confirmed diagnosis of SARS-CoV-2 infection within a five-day period with mild to moderate symptoms and were required to have at least one characteristic or underlying medical condition associated with an increased risk of developing severe illness from COVID-19. Each patient was randomized (1:1) to receive PAXLOVID or placebo orally every 12 hours for five days.

The scheduled interim analysis showed an 89% reduction in risk of COVID-19 related hospitalization or death from any cause compared to placebo in patients treated within three days of symptom onset (primary endpoint); 0.8% of patients who received PAXLOVID were hospitalized through Day 28 following randomization (3/389 hospitalized with no deaths), compared to 7.0% of patients who received placebo and were hospitalized or died (27/385 hospitalized with 7 subsequent deaths).

Similar reductions in COVID-19-related hospitalization or death were observed in patients treated within five days of symptom onset. In the overall study population through Day 28, no deaths were reported in patients who received PAXLOVID™ as compared to 10 (1.6%) deaths in patients who received placebo.

At the recommendation of an independent Data Monitoring Committee and in consultation with the FDA, Pfizer will cease further enrollment into the study due to the overwhelming efficacy demonstrated in these results.  Pfizer plans to submit the data as part of its ongoing rolling submission to the FDA for Emergency Use Authorization (EUA) as soon as possible. Meanwhile, Merck’s Molnupiravir became the world’s first oral COVID-19 pill to garner approval in the UK.

Pfizer is working to ensure access for its novel antiviral candidate for those most in need around the world, pending successful trial results and regulatory approval. Pfizer has also begun and will continue to invest up to approximately $1 billion to support the manufacturing and distribution of this investigational treatment, including exploring potential contract manufacturing options to help ensure access across low- and middle-income countries, pending regulatory authorization.

Author

Manju Bhaskar