For nearly twenty years, since the 1990s, Alzheimer's drugs have had difficult challenges and new drug approvals trickled to a stop despite large numbers of candidates. For news article see here and for an open access study see here.
A wide variety of drugs, against diverse targets, are under study today. The Us Against Alzheimer's organization has produced a comprehensive seven page infographic (a highlight screen shot is shown below). In addition to high-level timelines, the report provides a detailed six page table with further characteristics of each study included. Press release here; infographic seven page table as PDF, here.
The EU released new draft guidelines for Alzheimer drug approvals in January 2016 (here, here). In 2013, the Center for Medical Technology Policy (CMPT) produced a 29-page consensus document on evidence for Alzheimer drug trials (here).