Others see little cause for alarm. Merck & Co.’s newly approved oral drug works by generating mutations, raising hypothetical fears
The first oral antiviral for treating COVID-19, Merck & Co.’s molnupiravir, received approval from the U.K. Medicines and Healthcare products Regulatory Agency on 4 November. But the approval, for people at high risk of severe disease, comes as a prominent virologist has suggested using molnupiravir could do far more harm than good, potentially unleashing new, deadlier variants of SARS-CoV-2. Other virologists say the concern is worth tracking but is largely hypothetical, for now. “I don’t think we are in the position of withholding a lifesaving drug for a risk that may or may not happen,” says Aris Katzourakis, a viral evolution expert at the University of Oxford.
Molnupiravir, which Merck and Ridgeback Biotherapeutics developed from an earlier, experimental antiviral, works by interfering with viral replication, littering the viral genome with mutations until the virus can no longer reproduce. Last month, Merck and Ridgeback officials announced results of a clinical trial that found giving the drug to COVID-19 patients early in the disease reduced their risk of hospitalization and death by 50%. The drug’s ability to mutate RNA has raised persistent fears that it could induce mutations in a patient’s own genetic material, possibly causing cancer or birth defects; studies so far have not borne out those fears.
Now, William Haseltine, a virologist formerly at Harvard University known for his work on HIV and the human genome project, suggests that by inducing viral mutations, molnupiravir could spur the rise of new viral variants more dangerous than today’s. “You are putting a drug into circulation that is a potent mutagen at a time when we are deeply concerned about new variants,” says Haseltine, who outlined his concern Monday in a Forbes blog post. “I can’t imagine doing anything more dangerous.”
He notes that patients who are prescribed antibiotics and other drugs often don’t complete a prescribed medication course, a practice that can allow resistant germs to survive and spread. If COVID-19 patients feel better after a couple of days and stop taking molnupiravir, Haseltine worries viral mutants will survive and possibly spread to others. “If I were trying to create a new and more dangerous virus in humans, I would feed a subclinical dose [of molnupiravir] to people infected,” Haseltine says.