For decades, the global medical community has pinned its hopes on the amyloid hypothesis as the foundation for breakthrough treatments for Alzheimer’s disease, the progressive neurodegenerative condition that impacts millions of older adults worldwide. On Thursday, a gold-standard systematic review upended that long-held consensus, concluding that the much-touted class of anti-amyloid Alzheimer’s medications fails to deliver meaningful clinical benefits to patients – a finding that has already sparked fierce debate across the neuroscience and pharmaceutical sectors.
The analysis was conducted by the Cochrane Collaboration, an independent research organization widely recognized as the global gold standard for evidence-based synthesis of existing clinical data. The review focused on the entire class of drugs designed to target and clear amyloid beta plaques, the sticky protein clumps that accumulate in the brains of people living with Alzheimer’s, a hallmark of the disease that researchers have long theorized is its root cause.
After decades of expensive high-stakes research that yielded little progress, two newer anti-amyloid medications – lecanemab (marketed as Leqembi, developed by Biogen and Eisai) and donanemab (sold as Kisunla by U.S. pharmaceutical giant Eli Lilly) – were celebrated as transformative gamechangers when they debuted. Both secured regulatory approval from the United States Food and Drug Administration and the European Union within the last three years, bringing new hope to patients and their families grappling with the currently untreatable condition.
Even before the review was published, however, growing concerns about the drugs’ real-world effectiveness, exorbitant pricing, and dangerous side effects – including elevated risks of brain swelling and cerebral bleeding – had led to widespread caution. In the United Kingdom and France, for example, national public health systems have already declined to cover the treatments for most patients.
To conduct the most comprehensive analysis to date of this drug class, Cochrane researchers aggregated pooled data from 17 separate clinical trials involving more than 20,000 total participants, all of whom had either mild cognitive impairment or early-stage Alzheimer’s dementia. Across an 18-month average follow-up period, the trials evaluated seven distinct anti-amyloid drugs, with one trial focused on donanemab and another examining lecanemab.
While the drugs did successfully reduce amyloid plaque buildup in patients’ brains, as confirmed by brain imaging, that biological change did not translate into tangible, clinically meaningful improvements for patients, lead study author Francesco Nonino from Italy’s IRCCS Institute told reporters during a press briefing. “Even though early smaller trials reported statistically significant changes in disease progression markers, that improvement does not add up to a noticeable benefit for people living with Alzheimer’s,” Nonino explained.
Co-author Edo Richard, a neurologist at Radboud University Medical Center in the Netherlands, emphasized that the study’s findings directly challenge decades of core thinking in Alzheimer’s research. “The long-held hypothesis that removing amyloid plaques will improve patient outcomes is refuted by our results,” he said, adding that he hopes the findings will redirect research funding toward other potential biological mechanisms driving Alzheimer’s, which could yield more effective treatments down the line. “The current generation of these drugs is simply not delivering on the transformative promise that has been used to promote them,” Richard added.
Not all leading experts agree with the review’s conclusions, however. John Hardy, the British biologist who first proposed the amyloid hypothesis back in the 1990s, issued a scathing rebuke of the work. Hardy, who disclosed he has worked as a paid consultant for Eli Lilly, Biogen, and Eisai, argued that the review’s methodology was fatally flawed: it pooled data from the newer, more promising lecanemab and donanemab alongside older anti-amyloid drugs that were already known to be ineffective, dragging down the overall average of measured benefit. “This is a silly paper which should not have been published,” Hardy told AFP in an interview.
In response to the criticism, Richard defended the review’s approach, noting that while the included drugs may use slightly different mechanisms to attack amyloid, they all share the same core target: amyloid beta proteins, so grouping them for analysis is methodologically sound.
Other independent experts have struck a more moderate middle ground. Bryce Vissel, an Australian neuroscientist who was not affiliated with the research, noted that the review does not definitively prove that amyloid plays no role in Alzheimer’s development, nor does it rule out the possibility that future, improved amyloid-targeted therapies could one day help patients. Even so, Vissel acknowledged that the analysis delivers a clear, sobering conclusion: the current generation of widely hyped anti-amyloid drugs has not lived up to the lofty expectations that surrounded their arrival to the market.