Pfizer’s COVID-19 antiviral pill 89% effective against hospitalization
More positive data has been announced from a Phase 3 trial testing Pfizer’s novel antiviral pill developed to treat COVID-19. The final analysis revealed the five-day oral treatment reduced COVID-related hospitalizations and deaths by 89 percent in high-risk individuals.
Called Paxlovid, Pfizer’s antiviral is the first drug specifically designed to target SARS-CoV-2 to complete Phase 3 human clinical trials. The antiviral belongs to a class of drugs known as protease inhibitors.
Several protease inhibitors have been developed to target HIV and Hepatitis C. The drugs inhibit viral replication by blocking the action of a key enzyme the virus needs to multiply.
This particular antiviral has been in development for over a decade. Initially beginning development as a treatment for the original SARS virus that emerged in the early 2000s, the molecule was optimized to target SARS-CoV-2 in 2020.
The new data announced by Pfizer, yet to be peer-reviewed or published in a journal, covers a large Phase 2/3 trial. The trial enrolled over 2,200 subjects deemed to be at high-risk of severe COVID-19. This cohort was unvaccinated with at least one characteristic or medical condition associated with developing severe COVID-19.
The final results found those commencing the antiviral treatment within three days of symptoms appearing were 89 percent less likely to be hospitalized or die from COVID-19 compared to those taking a placebo. A secondary group commencing the treatment within five days of symptoms appearing showed similar efficacy. Overall there were no deaths in the Paxlovid group compared to 12 deaths in the placebo group.
“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,” says Pfizer CEO Albert Bourla. “This underscores the treatment candidate’s potential to save the lives of patients around the world.”
Paxlovid is also the subject of a few other ongoing Phase 3 trials in different populations. The latest Pfizer announcement includes interim data from a trial testing the antiviral in a “standard risk” population. This includes vaccinated high-risk subjects and healthy adults with no specific factor making them more likely to experience severe COVID-19.
In that trial the interim analysis reveals the antiviral treatment reduces hospitalizations and death by 70 percent compared to placebo. The trial is ongoing, fully enrolled and complete data is expected over the coming weeks.
Finally, Pfizer also announced the results of preliminary experiments testing Paxlovid’s activity against the Omicron variant. Initial lab data indicate the antiviral remains effective at inhibiting the key protease enzyme in Omicron. However, further work will be needed to confirm its real-world efficacy against Omicron.
The US Food and Drug Administration (FDA) has yet to issue emergency use authorization for Paxlovid but Pfizer has been supplying ongoing data from its trials and authorization is expected in the near future. The US government has already ordered 10 million courses of the antiviral treatment.