Shares of Eli Lilly & Co. /zigman2/quotes/200106384/composite LLY -0.34% gained 15.4% in premarket trading on Monday after the drugmaker said its experimental Alzheimer's disease drug helped slow the decline of cognition and daily function in patients with early forms of the disease when compared to those taking a placebo. Donanemab, an antibody-based treatment, targets the N3pG beta amyloid; it is currently being tested in a Phase 2 clinical trial, and Lilly said it expects to share full data from the study in the future. There are currently no treatments that slow cognitive decline that have been approved by the Food and Drug Administration. Lilly has studied Alzheimer's treatments for years, but like all pharmaceutical companies, it has struggled to find therapies that work against the disease. A year ago, another Lilly drug, solanezumab, failed a Phase 2/3 trial testing the treatment in people with or at risk for dominantly inherited Alzheimer's disease. Lilly's stock is up 20.6% over the last year, while the S&P 500 /zigman2/quotes/210599714/realtime SPX -2.45% has gained 19.7%.