An Alzheimer's drug is on the way, but getting it may still be tough. Here's why

In patients with Alzheimer's disease, a substance called beta-amyloid can form toxic clumps in between neurons. Drugs like lecanemab are designed to remove amyloid-beta from the brain. (National Institute on Aging, National Institutes of Health.)

The first drug shown to slow down Alzheimer's disease is likely to receive full approval from the Food and Drug Administration by July 6.

In theory, the move would make lecanemab (Leqembi) available to more than a million Medicare patients in the early stages of Alzheimer's. In practice, though, the number is likely to be much smaller.