In the 18-month trial, people in the early stages of Alzheimer's who received infusions of donanemab showed 35% less decline in thinking skills compared to those given a dummy drug, Lilly announced.

A new Alzheimer's drug isn't reaching many patients. Doctors say reasons include its high cost, and lingering questions about its effectiveness.

This is the first new drug approved for Alzheimer's disease since 2003. It's the first to show significant progress against the sticky brain plaques that are the hallmark of Alzheimer's disease.