(Reuters) -Cassava Sciences said on Monday it will stop all trials of its Alzheimer's disease drug after it failed a late-stage study, sending shares of the drug developer plummeting more than 80% before the bell.

The Cassava Sciences story ended Monday exactly as many knew it would — with the company’s experimental drug for Alzheimer’s disease, simufilam, failing a clinical trial.

Cassava Sciences shares are plunging in premarket trading and are losing most of their value after the biotech firm said its experimental Simufilam drug aimed at treating Alzheimer’s disease failed to show a “significant reduction in cognitive or functional decline” during the Phase 3 trial of the treatment.