Aducanumab’s approval and the cost of rushing hope

On June 7, 2021, the FDA granted accelerated approval to aducanumab for Alzheimer’s disease. It was the first new Alzheimer’s drug in nearly two decades, and one of the most controversial approvals in years.

For patients and families, the long gap is the context that matters most. Alzheimer’s is common, devastating and, so far, without a treatment that changes its course in a convincing way. Any approval was going to be met with enormous hope. That is exactly why this one deserves careful scrutiny.

The controversy

The drug clearly reduces amyloid plaques in the brain. Whether that translates into meaningful benefit for patients was far less clear, and the agency’s own advisory committee had recommended against approval.

Amyloid plaques are one of the defining features of Alzheimer’s, and for decades a leading hypothesis has been that they drive the disease. If that is true, clearing them should slow decline. Aducanumab does clear them. But reducing plaques and improving memory, thinking and daily function are not the same thing, and the evidence on the second point was mixed.

Accelerated approval exists for situations like this. It allows a drug to reach patients based on an effect on a marker that is reasonably likely to predict real benefit, with the requirement that the company confirms that benefit later. The mechanism has value. The question in this case is whether the marker was strong enough to justify the decision, given the uncertainty in the clinical data.

Be honest about the difference between changing a biomarker and changing a life.

My perspective

Alzheimer’s is personal for me; it is part of what drew me to studying how cells age. That is exactly why the evidence matters. Patients and families deserve hope, but they also deserve treatments proven to work.

I worry about what this approval signals. If a drug can reach the market mainly on its ability to change a biomarker, the incentive to prove clinical benefit becomes weaker. Patients may receive a treatment with real risks and costs without knowing whether it helps them. And a weak precedent can make it harder for better drugs to stand out later.

At the same time, I do not think the answer is to dismiss the amyloid field. The biology is real, and this approval may push for clearer trials that settle the question. What matters now is that confirmatory studies are designed rigorously and that their results, whatever they show, are acted on, even if they are disappointing.

The lesson

Aging research faces the same temptation. It is easier to measure a marker in the blood than to measure years of healthy life, and there will always be pressure to treat one as a stand-in for the other. Biomarkers are essential tools, but they are only meaningful when they are shown to track outcomes patients care about.

The lesson for researchers is to be honest about the difference between changing a biomarker and changing a life.