The Future of Alzheimer’s Treatment May Be Enlisting the Immune System

A new theory for Alzheimer’s disease is emerging, and at least one company is taking advantage of the new thinking with drugs in human trials

Illustration by Alexis Beauclair

The mood among the more than 3,000 researchers who gathered in Lisbon, Portugal, at the end of March for the 14th International Conference on Alzheimer’s and Parkinson’s Diseases was downbeat. Just a few days earlier, Biogen, the Cambridge, Massachusetts-based biotech company, and Japanese pharmaceutical company Eisai Co had jointly announced the shuttering of two major trials of their Alzheimer’s drug aducanumab. The announcement marked yet another failure in the decades-long effort to find a drug to halt the devastating course of the terminal, memory-robbing disease.

“There was a sort of pall over the meeting,” says Ron Petersen, director of the Mayo Clinic Alzheimer’s Disease Research Center in Rochester, Minnesota. Many speakers prefaced their remarks with a reference to the news. But, Petersen adds, “It’s going to encourage the field to broaden the potential therapeutic targets we have for the disease.”

Scientists in academic and corporate labs are already pursuing a host of new approaches that they hope will offer pathways out of the Alzheimer’s doldrums. One idea gaining traction takes a page from the oncology playbook, where drugs that enlist the power of the immune system to attack tumors are transforming cancer treatment and drug discovery.

Alector, a Silicon Valley startup founded six years ago, already has two Alzheimer’s drugs in early human studies designed to strengthen the ability of the brain’s immune system to fight the disease. One of the drugs targets a gene called TREM2 and the other a gene known as SIGLEC3; certain mutations in these genes can contribute to conditions that allow Alzheimer’s to develop. In May, Alector treated its first person with Alzheimer’s with its drug targeting TREM2, and has begun human testing for the drug that targets SIGLEC3 as well.

“If the immune system in the brain is not operating normally, the nerve cells cannot function normally,” says Arnon Rosenthal, a neuroscientist and co-founder and CEO of Alector. “Eventually they…