Why COVID sufferers in the US can’t get ensitrelvir, the antiviral drug better than Paxlovid

For people suffering through a bout of COVID-19, the antiviral Paxlovid has been a godsend.

The medication emerged as the go-to antiviral treatment during the pandemic after the Food and Drug Administration granted it emergency-use authorization in December 2021.

Now, there’s a new antiviral that’s superior to Paxlovid — but Americans can’t get it, as it’s being held up in the lengthy FDA-approval process.

Ensitrelvir, marketed as Xocova in Japan — the only country where it’s legally available — has several advantages over Paxlovid.

However, experts lament that the newer, better drug probably won’t be available in the US until the end of 2024.

The FDA seems to be “slow walking” the approval process for ensitrelvir, infectious disease specialist Dr. David Boulware, a professor medicine at the University of Minnesota, told the Atlantic.

And because the COVID-19 emergency was declared over in May of this year, ensitrelvir probably won’t be granted the same emergency-use authorization that Paxlovid received.

Nonetheless, the FDA has granted the new drug “fast-track” status, meaning its review process will be expedited once the drug’s manufacturer, Shionogi of Osaka, Japan, submits the required documentation.

Ensitrelvir vs. Paxlovid

Ensitrelvir has a number of advantages over Paxlovid and other antivirals.

People who take the drug test negative almost two days sooner than people who take a placebo. Symptoms like fever, congestion, sore throat, cough and fatigue disappear faster among some groups of people than with Paxlovid.

“Rebound” infections, in which symptoms recede and then seem to come back — common among Paxlovid users — have been rare among users of ensitrelvir. In addiction, the taste of ensitrelvir is unremarkable, according to anecdotal reports, whereas patients on Paxlovid have described the aftertaste as “a mouthful of dirty pennies and rotten soy milk.”

And ensitrelvir is easier to take, as it requires just once-a-day dosing, whereas Paxlovid users must take three pills twice daily for five days.

The two drugs have never been compared in head-to-head trials, however, so medical experts are reserving their enthusiasm for ensitrelvir until more data is available.

Loss of smell and taste

Despite this, a new study found that ensitrelvir effectively diminishes one of the most annoying and problematic effects of a COVID infection: loss of smell and taste.

After seven days, the percentage of study participants with smell or taste loss was 39% lower in a group taking ensitrelvir than in a placebo group.

“Most people will eventually recover on their own, but we know that some people have had long-term issues with smell and taste,” Dr. Yohei Doi, an infectious-disease researcher at Fujita Health University in Japan who worked on the ensitrelvir study, told Nature.

“When the omicron variants became dominant, the loss of taste and smell started to become less and less common,” Dr. Amesh Adalja, an infectious-disease specialist at the Johns Hopkins Center for Health Security, explained to Nature.

“But it still occurs, and it is a distressing symptom,” Adalja added. “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.”

The drugmaker Shionogi is continuing to conduct clinical trials into the safety and effectiveness of ensitrelvir among different user groups.