Pfizer's COVID-19 Oral Antiviral Shows In-Vitro Efficacy Against Omicron Variant

Pfizer Inc PFE yesterday shared results from multiple studies demonstrating the in-vitro efficacy of nirmatrelvir, the active main protease (Mpro) inhibitor of Paxlovid, is maintained against the omicron variant. 

• These in-vitro studies suggest that Paxlovid has the potential to maintain plasma concentrations many-fold times higher than the amount required to prevent Omicron from replicating in cells.
• In one lab study, Pfizer researchers tested nirmatrelvir against protease, an enzyme needed for the virus to generate copies of itself. Nirmatrelvir blocked the protease target in Omicron to the same degree it blocked the enzyme in the original strain, Pfizer said.
• Related: Canada Approves Pfizer's At-Home COVID-19 Antiviral Treatment, But Deliveries Delayed.
• In a second lab study, the resulting antiviral activity against Omicron was in line with activity Pfizer observed in several other variants of concern, including Beta and Delta.
• The third study, performed by researchers at the Icahn School of Medicine at Mount Sinai with Pfizer, measured nirmatrelvir's efficacy against Omicron and other strains and found approximately similar drug concentration was needed to block infection.
• Price Action: PFE shares are down 0.50% at $53.84 during the premarket session on the last check Wednesday.