Regulatory body sits at the center of this dementia and brain health question.

The European Medicines Agency’s Committee for Medicinal Products for Human Use (CHMP) has rejected Eli Lilly’s Kisunla (donanemab), signaling a significant regulatory shift in how European authorities evaluate new Alzheimer’s treatments. On March 28, 2025, the CHMP issued a negative opinion, concluding that the drug’s benefits do not outweigh the serious safety risks, particularly amyloid-related imaging abnormalities (ARIA) and brain swelling. While the drug received FDA approval in the United States, the European regulatory body took a more cautious stance, determining that slowing cognitive decline by up to 35% is insufficient to justify the neurological risks patients would face. This article explores the EU regulatory landscape for Alzheimer’s medications, examines which drugs have been rejected and why, discusses the specific safety concerns driving these decisions, and explains what these rejections mean for patients and caregivers seeking advanced treatment options.

Why Is the EU Rejecting New Alzheimer’s Drug Applications?
Which Alzheimer’s Drugs Have Been Rejected or Blocked in the EU?
What Are ARIA and Brain Swelling, and Why Do They Matter So Much?
Clinical Benefit Versus Safety Risk—How Do Regulators Make This Decision?
What Does the EU Rejection Mean for Patients and Caregivers?
The Re-Examination and Appeals Process
The Future of Alzheimer’s Treatments in Europe
Conclusion

Why Is the EU Rejecting New Alzheimer’s Drug Applications?

The European regulatory pathway for new medications involves rigorous evaluation where benefit-risk assessments determine approval. In recent cases—including Kisunla, Anavex’s blarcamesine, and others—the CHMP has found that the measurable cognitive benefits do not justify the documented safety risks. This represents a divergence from the FDA’s approval standards, which weighted the same clinical data differently and determined that the cognitive slowing benefit was meaningful enough for patients who might otherwise experience steeper decline. The EU’s more conservative approach reflects a policy priority: protecting patients from serious adverse events, even when a drug offers some therapeutic benefit.

Kisunla, which slows cognitive decline by up to 35% in early Alzheimer’s stages, was rejected precisely because that benefit, while notable, was weighed against documented cases of brain swelling and amyloid imaging abnormalities in clinical trials. The regulatory tension stems from how regulators define “acceptable risk.” In the United States, the accelerated approval pathway allowed a faster route to market with post-approval monitoring requirements. European regulators demanded stronger evidence that the cognitive benefit outweighed neurological safety signals before granting approval. This difference is not unusual—regulatory agencies worldwide sometimes reach different conclusions on the same data, reflecting different risk tolerances and patient populations.

Why Is the EU Rejecting New Alzheimer's Drug Applications?

Which Alzheimer’s Drugs Have Been Rejected or Blocked in the EU?

Eli Lilly’s Kisunla faced the most high-profile rejection to date. The CHMP issued its negative opinion on March 28, 2025, and as of March 2026, the re-examination process remains ongoing, meaning the door has not fully closed on potential approval. Another drug, blarcamesine from Anavex, took a different path—on March 25, 2026, Anavex withdrew its own EU marketing authorization application after the CHMP indicated a negative opinion was forthcoming, avoiding a formal rejection but removing the drug from European consideration.

Lecanemab (sold as Leqembi) initially received a negative CHMP opinion on July 26, 2024, but this case shows the process is not always final. By February 2025, the CHMP issued a positive opinion, and the European Commission’s decision process moved forward, suggesting that some drugs can overcome initial regulatory resistance through additional data or clarification. The staggered timeline of these decisions reveals that European regulators are evaluating each drug individually rather than applying a blanket policy against cognitive-decline-slowing agents. However, the pattern of rejections—particularly for drugs with documented ARIA risks—indicates a clear regulatory concern about the trade-off between modest cognitive benefits and neurological safety events.

What Are ARIA and Brain Swelling, and Why Do They Matter So Much?

Amyloid-related imaging abnormalities (ARIA) are changes visible on brain MRI scans that occur as a consequence of anti-amyloid drug therapy. There are two types: microhemorrhages (ARIA-H) and microinfarcts or swelling (ARIA-E). In Kisunla clinical trials, participants experienced documented cases of brain swelling, and while some were asymptomatic, others developed symptoms including headache, confusion, and neurological changes. The concern is not theoretical—these are real adverse events captured in safety data.

For regulators evaluating whether a drug should be approved, ARIA represents a significant safety signal that patients need to know about and that clinicians must monitor. Brain swelling (cerebral edema) is particularly concerning because it can lead to serious complications if not detected and managed promptly. Even asymptomatic swelling visible on imaging indicates that the drug is affecting brain tissue in ways beyond its intended mechanism. European regulators concluded that asking patients to accept this risk—requiring frequent MRI monitoring and the possibility of symptom-causing edema—in exchange for slowing cognitive decline by 35% was not a reasonable trade-off, especially when alternative treatments or monitoring strategies might be available. However, if a patient has already progressed to moderate Alzheimer’s and has few other options, their personal risk calculus might differ from the regulatory body’s population-level assessment.

What Are ARIA and Brain Swelling, and Why Do They Matter So Much?

Clinical Benefit Versus Safety Risk—How Do Regulators Make This Decision?

The core disagreement between the FDA and EMA reflects different philosophies about how much risk is acceptable. The FDA’s position was that a 35% slowing of cognitive decline represents a meaningful benefit for patients in early stages of the disease, particularly those facing a progressive and ultimately fatal condition. The European regulators asked a different question: Is a 35% slowing—which still results in cognitive decline, just at a slower rate—sufficient to justify asking patients to undergo regular MRI surveillance and accept the risk of brain swelling? The comparison matters because Kisunla does not stop cognitive decline; it does not reverse it. It modestly delays it.

For some patients and families, that delay is valuable and worth monitoring for safety signals. For regulators concerned about population-wide adverse events, the benefit-risk math did not work. This debate is not unique to Alzheimer’s drugs. It reflects a broader regulatory question about experimental therapies: Who gets to decide whether a modest benefit is worth a serious risk? Individual patients, their neurologists, and regulatory agencies may reasonably reach different conclusions. A patient in early Alzheimer’s stages who wants to extend their cognitive function for as long as possible might accept ARIA risks that a regulator reviewing population-level data might reject.

What Does the EU Rejection Mean for Patients and Caregivers?

For dementia patients and their families in Europe, these rejections eliminate an option that became available in the United States. A person diagnosed with early Alzheimer’s disease in the EU who might have considered Kisunla as part of their treatment strategy must look to other approaches—whether that is participation in clinical trials (which may be conducting European studies of donanemab), existing approved treatments like cholinesterase inhibitors and memantine, lifestyle interventions, or support services. The rejection creates a transatlantic disparity in available treatments, which can be frustrating for patients who learn that a drug is approved elsewhere but not in their country.

However, the stricter European standard also reflects a commitment to patient safety and requiring strong evidence before approving drugs with documented neurological risks. England’s National Health Service began reviewing the rejection of Lilly’s drug for NHS coverage on March 20, 2026, suggesting that even within Europe, there may be renewed discussions about whether the EMA’s position should be reconsidered. Patients and families should discuss with their neurologists what treatment options are available in their region and whether participation in ongoing clinical trials might offer access to emerging therapies.

What Does the EU Rejection Mean for Patients and Caregivers?

The Re-Examination and Appeals Process

Rejection by the CHMP does not necessarily mean permanent exclusion. Kisunla, for example, entered a re-examination process as of March 2026, meaning Eli Lilly has the opportunity to submit additional data or clarification to address the regulatory concerns. This might include newer safety data, reanalysis of the clinical trial data with a different focus, or emerging evidence of long-term safety from patients already taking the drug in approved markets. The process can take months or years, and outcomes are uncertain.

Some drugs successfully overturn initial rejections; others do not. Anavex took the opposite route with blarcamesine, withdrawing the application rather than facing a formal rejection. While withdrawal avoids a definitive regulatory “no,” it also means the drug is no longer under active European review, and the company would need to reapply from the beginning if it chose to pursue approval later. The strategic choice to withdraw versus proceed to rejection often depends on the company’s assessment of whether additional data could change the regulator’s mind.

The Future of Alzheimer’s Treatments in Europe

The pattern of recent rejections suggests that European regulators will continue to demand robust evidence of clinical benefit and careful management of safety risks before approving anti-amyloid or other disease-modifying Alzheimer’s therapies. This does not mean Europe will never approve drugs like Kisunla; it means the bar for approval is higher than in the United States, and companies seeking European authorization should prepare for intensive scrutiny of safety signals. Future drugs in development may incorporate design changes—such as lower doses to reduce ARIA risk, or companion biomarkers to identify patients at lower risk—specifically to meet European regulatory expectations.

Clinical research is also continuing in Europe, with ongoing trials that may generate the additional safety and efficacy data needed to shift regulatory perspectives. As the population ages and Alzheimer’s prevalence increases across Europe, regulatory agencies will face continued pressure to balance patient access to novel treatments against the imperative to protect against serious adverse events. The coming years will reveal whether the EMA’s current rejection stance becomes more flexible as additional long-term data emerges from the millions of patients taking approved drugs in other markets.

Conclusion

The European Medicines Agency’s rejection of Kisunla and withdrawal of blarcamesine from consideration represents a significant regulatory divide between Europe and North America on how to evaluate early-stage Alzheimer’s treatments. The EMA prioritized documented safety risks—specifically amyloid-related imaging abnormalities and brain swelling—over the clinical benefit of slowing cognitive decline by 35%, concluding that the trade-off was not favorable to patients at the population level. This does not mean these drugs will never be approved in Europe; Kisunla remains in a re-examination process, and lecanemab’s journey from initial rejection to positive opinion demonstrates that regulatory decisions can shift with new data or fresh analysis.

For patients and caregivers, understanding the EU regulatory position is important when considering treatment options or evaluating whether to participate in clinical trials. Discuss with your neurologist which treatments are available in your region, what the evidence shows about their benefits and risks, and whether enrollment in ongoing research might provide access to emerging therapies. As Alzheimer’s prevalence grows and research continues, the dialogue between patients, clinicians, and regulators about acceptable risk will likely evolve, potentially creating new pathways for drugs that currently face rejection.