the staff of the Ridgewood blog
NEW YORK NY, Pfizer Inc. (NYSE: PFE) today announced final results from an analysis of all 2,246 adults enrolled in its Phase 2/3 EPIC-HR (Evaluation of Protease Inhibition for COVID-19 in High-Risk Patients) trial of its novel COVID-19 oral antiviral candidate PAXLOVID™ (nirmatrelvir [PF-07321332] tablets and ritonavir tablets). These results were consistent with the interim analysis announced in November 2021, showing PAXLOVID significantly reduced the risk of hospitalization or death for any cause by 89% compared to placebo in non-hospitalized, high-risk adult patients with COVID-19 treated within three days of symptom onset. In a secondary endpoint, PAXLOVID reduced the risk of hospitalization or death for any cause by 88% compared to placebo in patients treated within five days of symptom onset, an increase from the 85% observed in the interim analysis. The EPIC-HR data have been shared with the U.S. Food and Drug Administration (FDA) as part of an ongoing rolling submission for Emergency Use Authorization (EUA).
“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,” said Albert Bourla, Chairman and Chief Executive Officer, Pfizer. “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.”
PAXLOVID is an investigational SARS-CoV-2 protease inhibitor antiviral therapy. It was developed to be administered orally so that, if authorized or approved, it can be prescribed at the first sign of infection or at first awareness of an exposure – potentially helping patients avoid severe illness (which can lead to hospitalization and death) or avoid disease development following contact with a household member who contracts COVID-19 – subject to the clinical success of the rest of the EPIC development program. Nirmatrelvir [PF-07321332], which originated in Pfizer laboratories, is designed to block the activity of the SARS-CoV-2-3CL protease, an enzyme that the coronavirus needs to replicate. Co-administration with a low dose of ritonavir helps slow the metabolism, or breakdown, of nirmatrelvir in order for it to remain active in the body for longer periods of time at higher concentrations to help combat the virus.
Nirmatrelvir is designed to inhibit viral replication at a stage known as proteolysis, which occurs before viral RNA replication. In preclinical studies, nirmatrelvir did not demonstrate evidence of mutagenic DNA interactions.
Current variants of concern can be resistant to treatments that are focused on the spike protein expressed on the surface of the SARS-CoV-2 virus, due to the mutations in this region. PAXLOVID, however, works intracellularly on the protease of the SARS-CoV-2 virus by inhibiting viral replication. Nirmatrelvir has shown consistent in vitro antiviral activity against the previously identified variants of concerns (i.e., alpha, beta, delta, gamma, lambda, and mu). In addition, nirmatrelvir potently inhibited the 3CL protease associated with Omicron in an in vitro biochemical assay. This indicates nirmatrelvir’s potential to maintain robust antiviral activity against Omicron. Additional in vitro antiviral studies with this variant are underway.
If authorized or approved, PAXLOVID will be administered at a dose of 300 mg (two 150 mg tablets) of nirmatrelvir with one 100 mg tablet of ritonavir, given twice-daily for five days. One box contains five blister packs of PAXLOVID, as co-packaged nirmatrelvir tablets with ritonavir tablets, providing all required doses for a full five-day treatment course.
