New clinical-trial data suggest that an antiviral pill called ensitrelvir shortens the duration of two unpleasant symptoms of COVID-19: loss of smell and taste. The medication is among the first to alleviate these effects and, unlike other COVID-19 treatments, is not reserved only for people at high risk of severe illness.

Early in the pandemic, roughly 40–50% of people with COVID-19 experienced impaired smell or taste. The antiviral drug molnupiravir speeds recovery of these senses, but generally only the most vulnerable people can take it.

That is not true for ensitrelvir. In Japan, where it received emergency approval last year, the drug is available to individuals with mild to moderate symptoms, regardless of their risk factors. Its developer, Shionogi in Osaka, Japan, is continuing to conduct clinical trials of the drug, which has not yet been approved outside Japan.

In one such trial, people with mild or moderate COVID-19 symptoms were given either 125 or 250 milligrams of ensitrelvir or a placebo. At the start of the study, 20% of participants reported some level of smell or taste loss. After the third day of treatment, the proportion of participants reporting such symptoms in the ensitrelvir groups started dropping more sharply than did the proportion in the placebo group. At day seven, the percentage of participants with smell or taste loss was 39% lower in the group taking 250-milligram pills than in the placebo group. Three weeks after treatment began, all groups reported similar symptom scores.

The findings were presented on 12 October at IDWeek, a meeting of infectious-disease specialists and epidemiologists in Boston, Massachusetts.

“Most people will eventually recover on their own, but we know that some people have had long-term issues with smell and taste,” says Yohei Doi, an infectious-disease researcher at Fujita Health University in Toyoake, Japan, and one of the study investigators.

A hallmark symptom dwindles

Smell and taste problems are less prevalent now than they were at early stages of the pandemic. “When the Omicron variants became dominant, the loss of taste and smell started to become less and less common,” says Amesh Adalja, an infectious-disease specialist at the Johns Hopkins Center for Health Security in Baltimore, Maryland. “But it still occurs, and it is a distressing symptom.”

Earlier this year, Shionogi reported that ensitrelvir shortens symptoms of COVID-19 by about a day — a standout trait, says Adalja. “What we’re trying to do is not just minimize severe disease, hospitalization and death, but also to minimize the disruption that an infection has on people’s activities.”

This article is reproduced with permission and was first published on October 17, 2023.