A New Attack on Alzheimer’s

The Obama administration has announced a bold research program to test whether a drug can prevent the onset of Alzheimer’s disease well before any symptoms appear. It is a long shot, but the payoff could be huge.

The prevailing, but not universally accepted, hypothesis is that amyloid plaques in the brain play a major role in causing Alzheimer’s. Crenezumab attacks the formation of such plaques, apparently by binding to amyloid proteins and clearing them from the brain. If the drug fails to work, the trial will probably demolish the amyloid hypothesis and set researchers scrambling to find other targets to attack.

Currently, there is no cure for Alzheimer’s, which steadily robs patients of their memory, followed by full-blown dementia. There is also no diagnostic test to identify who has it, and no treatment to slow patients’ deterioration for more than a few months. 

 

While work continues on those fronts, the new clinical trial will test whether the drug, Crenezumab, made by Genentech, can prevent the disease in a group of people whose genetic heritage guarantees that they will develop it. If the drug successfully prevents the loss of mental capacities as measured by a sensitive new cognitive test there is hope — but no guarantee — that it could do the same for members of the general public. As Pam Belluck described in The Times last week, the trial will focus on members of an extended family in Colombia who carry a rare genetic mutation that causes them to develop Alzheimer’s early in life. They typically experience cognitive impairment at about age 45 and dementia by 51. The trial will also include a smaller number of individuals in the United States with the same genetic mutation. 

Instead of recruiting thousands of volunteers and following them for an extended period as in a customary prevention trial, the researchers in Colombia will give the drug to only 100 people with the early-onset genetic mutation. They will give placebos to another 100 people with the mutation and to 100 family members who do not carry the deadly gene. 

The study will cost more than $100 million and is being financed mostly by Genentech, buttressed by $16 million from the National Institutes of Health and $15 million raised by the Banner Alzheimer’s Institute in Phoenix, which is leading the study. 

A prevention trial of a different drug that was also intended to slow formation of amyloid plaques actually made patients’ symptoms worse, possibly because it interfered with various other proteins needed by the brain. Researchers believe that Crenezumab will be safer and more effective, but again there are no guarantees. The risk is justified given that without the treatment the recipients will inevitably get Alzheimer’s in the prime of their lives. The truly big payoff will come if the drug succeeds in this group and lays the groundwork for preventing or slowing the progress of Alzheimer’s that appears late in life. The researchers will be gathering data on a variety of biomarkers — glucose activity in the brain, shrinkage of the brain, certain proteins in cerebral spinal fluid, for example — to see which if any are related to preventing amyloid plaques and the loss of mental abilities. 

If the drug prevents the deterioration of particular biomarkers and ultimately sustains mental capacity, then the same markers might be useful in identifying and treating older people likely to develop the disease. And federal regulators might be willing to approve other prevention drugs based on their short-term effects on biomarkers, speeding the conduct of clinical trials. 

More than five million Americans currently have Alzheimer’s. Without an effective preventive, the number will rise steadily as the population ages. 

Published: May 20, 2012  by NY Times, Editorial