Dimebon is a very promising drug for Alzheimer Disease. It's an old, safe, and cheap drug that was used in Russia as an antihistamine for several years. A key study ("Effect of dimebon on cognition, activities of daily living, behaviour, and global function in patients with mild-to-moderate Alzheimer's disease: a randomised, double-blind, placebo-controlled study.") was published in 2008 (
http://pubmed.gov/18640457) and concludes that dimebon is safe, well tolerated, and significantly improved the clinical course of patients with mild-to-moderate AD.