David Geldmacher: One of the biggest issues in coming up with effective therapies for Alzheimer’s disease is that we really don’t know critical elements [underlying] the mechanism [of the disease] in most people with the illness.
Why Drugs for Alzheimer’s Are So Hard to Develop
Dalmeet Singh Chawla

And because we are trying to reverse years of deterioration, effectively starting very late in the process of a chronic disease