Investigational Oral Antiviral Ensitrelvir Fast Tracked for COVID-19

The Food and Drug Administration (FDA) has granted Fast Track designation to ensitrelvir fumaric acid for the treatment of COVID-19.

Ensitrelvir is an investigational oral 3CL protease inhibitor designed to suppress the replication of SARS-CoV-2. The designation is supported by recent data from the phase 3 portion of the SCORPIO-SR study, which evaluated the efficacy and safety of ensitrelvir in patients with mild to moderate COVID-19 enrolled across Japan, South Korea, and Vietnam. Patients received either ensitrelvir 125mg, with an initial loading dose of 375mg (n=603), or placebo (n=600) orally once daily for 5 days, within 5 days of symptom onset.

Findings showed that treatment with ensitrelvir met the primary endpoint demonstrating a statistically significant reduction in the time to resolution of 5 symptoms of COVID-19, compared with placebo (167.9 hours vs 192.2 hours; median time difference, 24.3 hours; P =.0407). Moreover, a significant reduction in the time to achieve negative infectious viral titer (secondary endpoint) was observed in the ensitrelvir arm compared with the placebo arm (median time, 36.2 hours vs 65.3 hours; P <.0001).

The most common treatment-related adverse events reported in the study were temporary decreases in high-density lipoprotein and increased blood triglycerides. Overall, ensitrelvir was found to be well tolerated; no deaths or serious adverse drug reactions were reported.

“There is a need for additional COVID-19 treatment options as SARS-CoV-2 continues to affect people in the US. Receiving Fast Track designation from the FDA recognizes the potential of ensitrelvir as a once-daily, oral antiviral for SARS-CoV-2,” said Nathan McCutcheon, CEO, Shionogi Inc, the US subsidiary of Shionogi. “We look forward to our continued discussions with the FDA to bring ensitrelvir to patients as soon as possible.”

The Company is investigating the safety and efficacy of ensitrelvir in a wide range of COVID-19 patient populations in additional phase 3 clinical studies.