Scientists Hunt Ways to Stall Alzheimer's

Already, 5.4 million Americans have Alzheimer’s or related dementias. Barring a research breakthrough, those numbers will jump by 2050, when up to 16 million Americans are projected to have Alzheimer’s.

There is no cure, and the five medications available today only temporarily ease some symptoms. Finding better ones has been a disappointing slog: Over the last decade, 10 drugs that initially seemed promising failed in late-stage testing, Sperling said.

Moreover, scientists still don’t know exactly what causes Alzheimer’s. The chief suspects are a sticky gunk called beta-amyloid, which makes up the disease’s hallmark brain plaques, and tangles of a protein named tau that clogs dying brain cells. One theory: Amyloid may kick off the disease while tau speeds up the brain destruction.

Previous studies of anti-amyloid drugs have failed, but that new international study will test a different one, in a different way: About 300 people from a huge extended family in Colombia who share a gene mutation that triggers Alzheimer’s in their 40s will test an experimental drug, Genentech’s crenezumab, to see if it delays onset of symptoms. The study also will include some Americans who inherit Alzheimer’s causing gene mutations.

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