Jennifer Couzin-Frankel in Science:
Last week’s announcement by drug behemoth Pfizer that its 5-day pill regimen powerfully curbs many early SARS-CoV-2 infections opens a new chapter in the battle against the virus. In a clinical trial that an independent monitoring group halted early because the experimental therapy appeared so effective, it slashed hospitalizations by 89% among those treated within 3 days of symptom onset. If Pfizer’s drug candidate passes muster with regulators, it could join molnupiravir, a pill recently developed by Merck & Co. that received approval last week in the United Kingdom, as the first oral medications proved to stop COVID-19 from progressing to severe disease.
Such antivirals, public health experts and scientists say, could help a broad swath of people, including the unvaccinated and those who develop breakthrough infections despite vaccination. If affordable enough—a still unresolved question—the pills could also act as a crucial safety net for low-income countries that have struggled to obtain vaccines and that have more limited hospital resources.
The Pfizer antiviral is a protease inhibitor, a well-studied drug class that targets key enzymes in many viruses and that has already revolutionized the fight against HIV. “This looks like an oral medication that really works,” says Oriol Mitjà, a physician-scientist who studies and treats infectious disease in Papua New Guinea and is affiliated with the Germans Trias i Pujol University Hospital. Although neither company has provided much data publicly, Pfizer’s compound appears more effective than molnupiravir, which has a different mechanism. Together, however, the two antivirals could transform the pandemic’s course. Although they “can’t replace vaccines,” says Nahid Bhadelia, an infectious disease doctor at Boston University, they can help “our return to normalcy.”