Scientists have raised concerns over the antiviral drug, molnupiravir, used to treat Covid-19, suggesting that it may be contributing to the evolution of new variants of the virus. While the drug is designed to destroy the virus through mutation, researchers have found evidence suggesting that the virus can sometimes survive the treatment and produce mutated versions. These mutations increase the genetic diversity of the virus and provide more opportunities for future evolution. However, there is currently no evidence that these mutations have made the virus more dangerous.
The implications of these findings are significant for assessing the risks and benefits of molnupiravir and other similar drugs under development. The researchers have identified hallmark mutations in Covid viruses from 2022, after the introduction of molnupiravir. These signature mutations have been found to be more common in countries where molnupiravir was extensively used, including the UK, Australia, the US, and Japan. Moreover, the mutations were more frequently detected in Covid virus samples taken from older patients who were more likely to be treated with the drug. The researchers also found that viral samples with the signature mutations were more likely to come from patients who had received molnupiravir treatment.
Although the implications of these mutations remain unclear, as there are no widely circulating variants with the signature mutations and most mutations tend to weaken the virus rather than make it more dangerous, scientists are investigating whether drug-induced mutations explain the observed rise in virus levels in the Panoramic trial of molnupiravir. The trial found that while the drug initially reduced virus levels, levels appeared to rise again at two weeks, potentially indicating the creation of mutated versions that can evade patients’ immune defenses. Moreover, the trial also revealed that molnupiravir did not reduce the risk of hospitalisation or death among vaccinated, high-risk patients facing the Omicron variant, but it did speed up recovery time.
Experts suggest that molnupiravir may still have value in specific contexts, such as speeding up recovery among essential workers during times of high pressure on healthcare services. However, caution is advised against using it as a universal treatment. The manufacturer of molnupiravir, MSD, has stated that the drug impairs viral replication and reduces shedding, thereby lowering the risk of transmission. They argue that the assumptions made by the study authors about viral spread from molnupiravir-treated patients lack documented evidence.