What the Alzheimer’s Drug Breakthrough Means for Other Diseases

It’s been three decades since scientists hypothesized that Alzheimer’s is caused by a buildup of amyloid beta protein in the brain. But it wasn’t until last month that drugmakers achieved a major breakthrough, with Japan’s Eisai Co. and its US partner Biogen Inc. releasing results from a large-scale trial showing they were able to blunt the disease’s progression. The companies are seeking accelerated US approval for the medication, lecanemab, though questions remain about the extent of the benefits, side effects, and how it would be covered by insurers if approved.

Finding a winning treatment for dementia, thought to afflict more than 55 million people globally, has been the life’s work of Eisai Chief Executive Officer Haruo Naito, the 74-year-old grandson of the company’s founder. He oversaw the launch of a predecessor drug in 1997—sold under the brand name Aricept—that improved mental function but didn’t slow the advancement of Alzheimer’s, the most common type of dementia. The commercial failure of another Alzheimer’s drug from Eisai and Biogen, Aduhelm, makes the success of lecanemab particularly meaningful. Here, Naito shares the importance of the discovery and why he’s confident about gaining regulatory approval. The interview has been edited for clarity and length.