Ensitrelvir Pill Reduces COVID-19 Infection Risk After Exposure

Post-Exposure Prophylaxis Results

In a phase 3 trial, ensitrelvir—known as Xocova—showed a 67% reduction in risk of covid infection in patients treated after exposure.

According to a study published in the New England Journal of Medicine (NEJM), the drug was effective when administered to household contacts of a patient with COVID-19. For the prophylaxis to be effective, the medication had to be administered within 72 hours after the index patient first experienced symptom onset.

Regulatory Status and Availability

Ensitrelvir has already received approval for use in Japan. However, the drug is currently awaiting approval from the U.S. Food and Drug Administration (FDA) for use in the United States.

Comparison to Other Treatments

Other oral medications have been evaluated for similar preventative purposes with varying results. Paxlovid, a combination of nirmatrelvir and ritonavir, was developed for both COVID-19 treatment and post-exposure prophylaxis. In Paxlovid, ritonavir functions to shut down the metabolism of nirmatrelvir in the liver to prevent it from leaving the body too quickly.

However, a placebo-controlled trial published in the NEJM found that post-exposure prophylaxis using nirmatrelvir–ritonavir for either 5 or 10 days did not significantly reduce the risk of symptomatic COVID-19.

Other medications, such as the pill baricitinib, have been used to treat COVID-19 by acting as an antiviral and lowering inflammation. Additionally, separate clinical trials have investigated whether common nasal antihistamine sprays may also prevent COVID-19.