One of the news topics in the world of Alzheimer's this week is the use of Carmustine, a compound related to mustard gas that is used "as an akylating agent in chemotherapy", as a possible treatment to reduce the buildup of amyloid beta plaques in the brain. The investigation into Carmustine was initiated because it has been previously noted that cancer patients have a lower rate of Alzheimer's and Alzheimer's patients have a lower rate of cancer.
Carmustine has been found to reduce the plaques in mice models by up to 75%. The dose needed to achieve this is lower than the dose currently used to treat some brain cancers.
It is an interesting possibility.