Carl Zimmer -- April 24, 2026
The dual setback — a denied priority review and a safety board's call to pause new enrollment — sent shares in the tau-targeting antibody's developer tumbling nearly 28 percent.
Eisai's TREM2-targeting Alzheimer's drug candidate encountered two significant regulatory setbacks this week when the Food and Drug Administration declined to grant priority review and an independent data safety monitoring board recommended pausing new patient enrollment pending a full safety review.
The FDA's decision to deny priority review means the application will proceed under a standard twelve-month review timeline rather than the expedited six-month process Eisai had sought. Priority review is typically reserved for drugs that address serious conditions and may offer substantial improvements over available therapies.
The independent data safety monitoring board, which reviews blinded trial data at pre-specified intervals and operates separately from the drug's developer, recommended the enrollment pause after reviewing the available safety data. Eisai stated that the safety events observed were within expected parameters but acknowledged that the pause was in effect. An enrollment pause is distinct from a trial halt; existing participants may continue using the device while the board conducts its review.
Eisai said it would work with the FDA to expedite a response to the safety board's concerns and expected to provide a public update within 90 days.
Shares in Eisai fell 27.8 percent on the day of the announcements, reflecting investor concern that the data safety monitoring board's flag could delay the programme or require protocol modifications that extend the development timeline.