Slowing decline is not the same as restoring what has been lost
Across three continents, regulatory bodies examined identical clinical evidence for amyloid-targeting Alzheimer's therapies and arrived at divergent verdicts — a disagreement that exposes not bureaucratic failure but a deeper philosophical reckoning with what constitutes meaningful medicine. Drugs like donanemab and lecanemab slow cognitive decline modestly, carry measurable risks of brain injury, and cost more than many health systems are willing to bear for the benefit they deliver. As 78 million people are projected to live with dementia by 2030, the question these regulators are really asking is an ancient one: when suffering cannot be reversed, how much risk and expense is owed to those who might be spared a little more of it?
- The same clinical trial data led the FDA and UK to approve donanemab while European regulators initially rejected it — a split that signals genuine scientific uncertainty, not mere procedural difference.
- Nearly 37% of patients in donanemab's pivotal trial developed brain microbleeds or swelling, a documented harm that forces every prescribing decision into a careful calculus of modest gain against real injury.
- Even where approval was granted, access collapsed: the UK's NHS declined to fund either drug, ruling that a 27–35% slowing of decline did not justify the cost — until caregiver burden was factored into the appeal.
- The scientific premise itself is contested, as some researchers question whether clearing amyloid changes the disease or merely cleans a marker, leaving the entire therapeutic strategy philosophically unresolved.
- Over 150 new drugs are in development targeting inflammation, metabolism, and infection, with trials now reaching people who carry genetic risk but show no symptoms yet — a sign the field is moving beyond its founding assumption.
Three regulatory agencies reviewed the same evidence for new Alzheimer's drugs and reached three different conclusions. The FDA and UK approved donanemab in 2024. The European Medicines Agency initially said no, citing safety concerns serious enough to warrant rejection. The split reveals something deeper than bureaucratic disagreement: a fundamental uncertainty about whether slowing a disease's progression constitutes meaningful treatment when the costs and risks are high.
The drugs target amyloid-beta, the protein that accumulates in Alzheimer's brains. Donanemab reduced disease progression by roughly 35 percent over 72 weeks in early symptomatic patients; lecanemab showed 27 percent slowing over 18 months. These are not cures. They do not reverse symptoms. Yet for people watching their minds deteriorate, even modest slowing can feel worth pursuing.
The safety profile complicates that calculation. Nearly 37 percent of patients treated with donanemab developed amyloid-related imaging abnormalities — microbleeds and brain swelling visible on MRI — compared to 15 percent on placebo. Serious events occurred in 1.6 percent of treated patients. Doctors can manage these risks through genetic screening and regular monitoring, but management is not prevention.
The EMA eventually approved donanemab, but only for patients carrying one or no copies of the APOE4 gene. Lecanemab followed a similar path: initial rejection, then restricted approval. An earlier drug, aducanumab, received accelerated FDA approval in 2021 but was withdrawn in 2024 after failing to demonstrate clinical benefit — suggesting regulators are adjusting their tolerance for risk as evidence accumulates.
Access remained a separate obstacle. In 2025, the UK's NICE ruled that neither drug would be routinely funded by the NHS, concluding the cost did not justify the modest benefit. Both drugs later returned for re-evaluation after an appeal that highlighted the burden on unpaid caregivers — a reminder that a 35 percent slowing of decline might mean an extra year of recognizing family members, of maintaining some autonomy, even if that value resists easy calculation.
The scientific foundation itself is contested. Some researchers question whether removing amyloid actually alters the disease or merely reduces a biological marker. The field is already shifting in response: more than 150 drugs are in development targeting brain inflammation, metabolic dysfunction, and infection. Trials are expanding to people at high genetic risk who have not yet developed symptoms. Experimental approaches like trontinemab and subcutaneous home-administered injections aim to reduce both side effects and the burden of hospital monitoring.
With dementia cases projected to rise from 55 million in 2020 to 78 million by 2030, the urgency is undeniable. But the regulatory disagreements and access barriers make clear that approving a drug is not the same as delivering it to patients — and that slowing decline is not the same as restoring what has already been lost.
Three regulatory agencies looked at the same clinical evidence for new Alzheimer's drugs and reached three different conclusions. The US Food and Drug Administration approved donanemab in 2024. The UK's medicines regulator approved it too. The European Medicines Agency said no—at least at first, citing safety concerns serious enough to warrant rejection. This regulatory split, playing out across the Atlantic and within Europe, reveals something deeper than bureaucratic disagreement: a fundamental uncertainty about whether slowing the progression of a disease counts as meaningful treatment when the cost and risk are high.
The drugs in question target amyloid-beta, the sticky protein that accumulates in Alzheimer's brains and has long been suspected as a primary driver of cognitive decline. Donanemab reduced disease progression by about 35 percent over 72 weeks in early symptomatic patients, measured on a standard cognitive rating scale. Lecanemab, approved earlier, showed a 27 percent slowing of decline over 18 months. These are not cures. They do not reverse symptoms. They slow the inevitable slide, and only modestly. Yet for people watching their minds deteriorate, even modest slowing can feel like something worth pursuing.
The safety profile complicates the calculation. Both drugs carry a risk of amyloid-related imaging abnormalities—ARIA, in the medical shorthand—which manifests as microbleeds and brain swelling visible on MRI scans. In donanemab's pivotal trial, nearly 37 percent of treated patients developed ARIA, compared to 15 percent in the placebo group. Serious ARIA events occurred in 1.6 percent of those treated. These are not theoretical risks. They are documented harms that emerge in a meaningful fraction of patients. Doctors can manage ARIA through genetic testing, regular brain imaging, and close monitoring, but management is not prevention, and monitoring is not costless.
The regulatory disagreement reflects a genuine philosophical divide about how to weigh modest benefit against documented risk. The EMA eventually approved donanemab, but only for patients with one or no copies of the apolipoprotein E4 gene—a restriction based on additional safety data and a narrower patient population. Lecanemab followed a similar path: initial European rejection, later acceptance with restrictions. Aducanumab, an earlier amyloid-targeting drug, received accelerated FDA approval in 2021 but was withdrawn from the market in 2024 after failing to demonstrate clinical benefit in subsequent trials. The pattern suggests regulators are learning as they go, adjusting their tolerance for risk as evidence accumulates.
Access remains a separate problem. In 2025, the UK's National Institute for Health and Care Excellence ruled that donanemab and lecanemab would not be routinely funded by the National Health Service. The cost did not justify the modest clinical benefit, the agency concluded. Both drugs later returned for re-evaluation after an appeal that highlighted the burden on unpaid caregivers—a reminder that the value of a treatment extends beyond what clinical trials measure. A 35 percent slowing of decline might mean an extra year or two of independence, of recognizing family members, of maintaining some autonomy. That has weight, even if it does not appear in a cost-effectiveness calculation.
The scientific foundation itself remains contested. Many researchers question whether removing amyloid actually alters the disease course or merely reduces a biological marker associated with it. The Nun Study, a long-running investigation of Catholic sisters, documented one nun—Sister Mary—who maintained sharp cognitive function until her death despite extensive amyloid plaques found at autopsy. One case does not overturn a theory, but it illustrates the gap between what we can measure in the brain and what we can predict about a person's mind.
The future treatment landscape is already shifting. More than 150 new drugs are in development, targeting mechanisms beyond amyloid: brain inflammation, infections, metabolic dysfunction. Clinical trials are expanding into earlier populations—people at high genetic risk who have not yet developed symptoms. An experimental drug called trontinemab shows promise for clearing amyloid with fewer side effects, and researchers are exploring subcutaneous injections that patients could administer at home, reducing the burden of hospital visits and frequent monitoring. These approaches reflect a broader recognition that Alzheimer's is not a single disease but a constellation of biological processes, and that one-size-fits-all treatment is unlikely to work.
The global burden of dementia is projected to rise from 55 million cases in 2020 to 78 million by 2030. That arithmetic alone justifies the search for better treatments. But the regulatory disagreements and access barriers reveal that approving a drug is not the same as making it available to patients who need it, and that slowing decline is not the same as restoring what has been lost. The path forward requires not just new drugs but new thinking about how to test them, how to measure their value, and how to ensure that the people most likely to benefit can actually access them.
Citas Notables
Many scientists question whether removing amyloid actually alters the disease course or merely reduces a biological marker associated with it— The Lancet World Report
Health experts suggest that new drugs should aim to improve quality of life for Alzheimer's patients rather than simply altering lab test results— Health experts cited in the report
La Conversación del Hearth Otra perspectiva de la historia
Why do regulators disagree so sharply if they're looking at the same trial data?
Because the data itself is ambiguous. A 35 percent slowing of decline sounds meaningful until you realize it means some patients still decline significantly, and 37 percent develop brain imaging abnormalities. Different agencies weight that trade-off differently based on their mandate and their tolerance for risk.
But if a drug slows decline, shouldn't that be enough?
Only if you believe slowing decline is the goal. Some regulators ask: does this actually improve how patients live, or does it just change a number on a test? And at what cost? The UK decided the cost was too high relative to the benefit, even though the drug was approved elsewhere.
What about the patients who want to try it anyway, even with the risks?
That's the real tension. A person facing cognitive decline might accept brain microbleeds for a chance at extra time. But regulators have to think about populations, not individuals. They have to ask whether it's responsible to approve something for millions when serious side effects appear in thousands.
Is amyloid even the right target?
That's the question keeping researchers up at night. We've been chasing amyloid for decades, but Sister Mary had a brain full of amyloid plaques and stayed sharp her whole life. It suggests amyloid might be necessary for Alzheimer's but not sufficient. Maybe we're treating a symptom, not the disease.
So what changes?
Earlier detection in people at risk before symptoms appear. Testing drugs that target inflammation, infection, metabolism—the other things that might drive cognitive decline. And honestly, listening more to what patients actually want from treatment, not just what biomarkers improve.
Will that take a long time?
Yes. But the alternative is approving drugs that slow decline modestly while carrying real risks, then arguing about whether they're worth the cost. We need a better foundation first.