Almost as quickly as Covid-19 erupted in early 2020, so too did the rush to find drugs, either old or new, to treat the contagion spreading around the world. While researchers soon identified some that quelled late-stage symptoms or weakly restrained the virus, Paxlovid, a pill from Pfizer Inc. that prevents severe disease, appears poised to take a solid lead in the lucrative coronavirus treatment market.
Yet an important component of Pfizer’s antiviral has links to a drug from rival Merck: boceprevir, developed decades ago to fight hepatitis C. That fragment accounts for at least 20% of Paxlovid’s coronavirus-fighting power—and perhaps much more—researchers estimate, and a key patent on the larger molecule it comes from still resides with Merck.
