Nature News evaluated antiviral drugs developed for the treatment of Covid-19.
Clinical-trial data showed that molnupiravir, developed by the pharmaceutical firm Merck, based in Kenilworth, New Jersey, and the biotechnology company Ridgeback Biotherapeutics in Miami, Florida, cut hospitalizations and deaths by 30%, compared with people who took placebos. Meanwhile, Paxlovid (nirmatrelvir and ritonavir), made by Pfizer, based in New York City, cut hospitalizations and deaths by 89%. UK regulators approved molnupiravir in November and Paxlovid in December, and US regulators granted emergency authorizations for both drugs in December.
Paxlovid inhibits SARS-CoV-2’s main protease, whereas molnupiravir tricks its RNA polymerase into incorporating part of the drug into the virus’s RNA, creating so many errors that it cannot survive. A third drug — remdesivir, developed by Gilead, based in Foster City, California — inhibits RNA polymerase, but treatment is expensive and currently requires intravenous infusions over three consecutive days, making it inaccessible to many people.
If the treatment does not completely wipe out the virus in a patient, some of the RNA errors it creates might inadvertently give the virus resistance against the other drug in the combination. That’s why it’s a key priority for researchers to find an accessible drug that effectively blocks the virus’s RNA polymerase, which could be used in partnership with a protease inhibitor such as Paxlovid. One option may be an oral version of remdesivir, which Gilead is currently testing.