Covid-19 virus may develop resistance to antiviral treatments, study finds

The general press often mentions the problem of bacterial resistance, or multi-resistant superbugs, as threats to human health. While the Covid-19 virus, or sars-Cov-2, has been part of our lives for more than 4 years now, we can wonder about its risk of rresistance to antiviral treatments. Because viruses, by mutating, can, like bacteria, develop resistance to usual treatments.

In a new study, published on September 25, 2024 in the JAMA Network Open (Source 1), American researchers report having observed a phenomenon of resistance on the part of the Covid-19 virus. The study focused on two antivirals, nirmatelvir et remdesivirthe first being one of the active ingredients of Paxlovid®, Pfizer’s drug against Covid-19, and the second, marketed under the name Veklury® and intended for patients for whom Paxlovid® is contraindicated. If one is in tablet form and the other is injectable only, these two antivirals both reduce the risk of serious illness in people at risk.

Overall, the study followed 156 people, including 73.1% womenmedian age of 56 years. Among these participants, 63 people did not receive any treatment for Covid-19, 79 received nirmarelvir, and 14 received remdesivir. Nasal swabs were taken to look for the presence of RNA of the virus, to sequence it, and to look for possible drug resistance mutations.

This is how scientists have demonstrated mutations giving the virus resistance to nirmarelvir, in nine patients who took this drug, and two others who took something else. In people treated with nirmarelvir, this resistance to the antiviral appeared more frequently in the most immunocompromised peoplethose with the most weakened immune systems.

However, more than 90% of these mutations were only detected at very low concentrations, and turned out to be transient. The virus thus quickly returned to its initial state. Researchers thus speak of so-called mutations “low frequency”, et “transient in nature”, and believe that there is therefore no cause for alarm. All this “suggests low risk of community spread of nirmarelvir resistance with current variants and patterns of drug use”, wrote the researchers in a press release (source 2). The study at least has the merit of recalling the importance of monitoring the Sars-Cov-2 virus, which has already shown its ability to mutate, and therefore to escape the immune system, to a certain extent.