On any list of biotech plays that might multiply in value in a relatively short period, Cassava Sciences (NASDAQ: SAVA) is likely to be near the top of the list. It's exploring whether its drug called simufilam is safe and effective to treat early-stage Alzheimer's disease, though its clinical trials have (so far) shed little light on the issue. The biggest reason to sell Cassava stock: After an open-label phase 2 clinical trial of simufilam, the market reacted quite negatively to the release of new data that management spun as being positive.