Merck announced at the beginning of October that its drug candidate, molnupiravir (an oral antiviral), had been shown to reduce the risk of death or hospitalization from Covid-19 in high-risk patients within five days. Merck has applied for emergency authorization from the Food and Drug Administration. The drug could be rolled out in the latter part of this year. The United States has ordered nearly 1.7 million doses of the drug. The United Kingdom has almost half a billion.
Merck has made the drug widely accessible to the world, a drastic departure from other major vaccine producers. Merck has reached agreements with Indian companies to manufacture the drug and sell it in more than 100 countries, mostly in Africa and Asia. Although the company expects to produce 10,000,000 courses by the end this year, it still needs approval from local regulators. This is good news for economically poor countries that need a quick and affordable treatment to help them get vaccines. It's also notable because it's the first Covid-19 drug you can take in a pill. The only approved antiviral treatment currently in the US and UK is Remdesivir. It has limited but useful effects. However, it can speed up recovery. It is expensive and difficult to make and requires injection through an IV.
Antiviral resistance is often a side effect of antiviral medications. You rarely get one without the others. Scientists worry that the virus may soon be able to defeat the antiviral drugs' attack mode and that this will increase the risk of resistance. Saye Khoo is a Professor of Pharmacology at University of Liverpool and an Antiviral Researcher. The history of antivirals has been littered by resistance. This has been a problem with influenza treatment for a long time: There is a whole class FDA-approved antiviral drugs now that the influenza virus has outwitted them.
Antiviral drugs that are likely to be used in large numbers will need to be monitored for signs of resistance. We need to be aware of the possibility of resistance to any antiviral drug. Daniel Kuritzkes is chief of Brigham and Women's Hospitals infectious disease division and professor at Harvard Medical School. For most of the drugs that we use, resistance has been seen.
A virus infects a person's body and makes copies inside the cells. Its own replication machinery creates copies, similar to a photocopier. Injecting an antiviral such as molnupiravir to the mix is similar to inserting paper that looks very similar. The photocopier does not spot the imposter and incorporates the defective component into its DNA, effectively nuking itself out.
SARS-CoV-2 may be able to outwit the drug. Any variant that is less sensitive to the drug's modus operandi might survive and become more dominant. This could lead to resistance. SARS-CoV-2 already has shown the ability to outwit certain treatments. In fact, the US stopped shipments of Eli Lilly's antibody therapy in July 2021 after discovering resistance in newer versions of the virus.
