Cassava Sciences shares fall 10.88% after-hours as FDA places full clinical hold on simufilam epilepsy trial, delaying 2026 launch plans.

Cassava Sciences Inc. fell 10.88% in after-hours trading following the U.S. Food and Drug Administration placing a full clinical hold on its proposed proof-of-concept trial for simufilam in tuberous sclerosis complex (TSC)-related epilepsy. The FDA required additional pre-clinical data and protocol modifications, delaying the trial beyond the first half of 2026. The biotech company, which previously discontinued simufilam’s Alzheimer’s program after negative results, now faces further setbacks as it must address the FDA’s concerns before advancing its TSC-related epilepsy study. The move exacerbates investor concerns over the drug’s development timeline and therapeutic potential, with the stock now on track for its worst after-hours decline amid prolonged regulatory hurdles.