Pfizer to Address COVID-19 Reinfection After Paxlovid Treatment

On Tuesday, the US Department of Health reported that Pfizer’s oral antiviral treatment – Paxlovid increased 315% over the past four weeks due to rising COVID-19 cases, with the CDC re-recommending masks for public transportation. 

As the United States’ main COVID-19 treatment, researchers are now mouthing concerns on possible drug resistance to Paxlovid following reports of reinfection. Pfizer has denied research supplies for unexplained reasons, some academic researchers said they cannot obtain Paxlovid for studies that could improve effectiveness, expand use, and counter drug resistance. However, Pfizer is now in talks with the US National Institutes of Health to discuss plans for addressing COVID-19 reinfections, it also indicated a second course of Paxlovid could treat reinfections.

Related article: FDA Limits Use of Johnson & Johnson COVID Vaccine Due to Blood Clot Risks 

COVID-19: Variants vs Therapeutics

Paxlovid, granted FDA emergency use authorization (EUA) in December 2021, is a combination of nirmatrelvir which inhibits a SARS-CoV-2’s replication, and ritonavir which slows down nirmatrelvir’s breakdown to ensure potency. SARS-CoV-2’s frequent mutations are prompting researchers to initiate combination studies; the combination of Paxlovid with other drugs could be the next step forward.

Last month, GSK’s COVID-19 monoclonal antibody drug – Sotrovimab had its EUA revoked by the FDA in less than a year in wake of the Omicron variant, since then, FDA is evaluating efficacy of approved new COVID-19 treatments on a rolling basis. In January, the FDA announced usage restrictions for two monoclonal antibody drugs: Eli Lilly’s bamlanivimab and etesevimab antibody cocktail, and Regeneron’s REGEN-COV (casirivimab and imdevimab). Following FDA’s decisions, mainstream treatment options are mostly oral drugs including Pfizer’s Paxlovid, MSD’s molnupiravir, and Gilead’s remdesivir.

Pfizer believes the drug’s short treatment period and high concentration “suggest the chances of resistance are minimized,” a spokesperson told Bloomberg and added that the company is actively monitoring mutations and will use the findings to design follow-up drugs.

Author

Fujie Tham