This appears to be the trial Glenda referenced:

Novartis Tests New Alzheimer’s Drugs on People Who Don’t Have the Disease

Subjects at high risk of developing Alzheimer’s—but who don’t actually have the disease—are being recruited to help test two experimental treatments from Novartis AG, in a new focus on preventive treatment.

https://apple.news/Ab2fBJKiiTVGSLnwjgpITPQ

New article in The Wall Street Journal with some detail how the subjects will be selected.