I've found no evidence, either, of homotaurine being effective against developing AD. In fact, there is evidence that it is no more effective than placebo.
Here's one article written for the layperson by a pharmacology specialist:
http://www.irishtimes.com/newspaper/health/2010/0216/1224264543985.html
In general, it seems the amyloid plaque theory of Alzheimer's Disease is losing favor. (Seems I recall that the Nun Study showed that older nuns in the sample with good brain function also displayed signs of this plaque post-mortem.)
It's important to keep in mind that dementia has many causes, including hypertension.