A sweeping Cochrane review has reignited debate over the effectiveness and safety of amyloid-targeting Alzheimer’s drugs, producing a sharp divide among scientists, drugmakers, and advocacy groups.

The analysis examined data from 17 clinical trials involving 20,342 participants with mild cognitive impairment or early-stage Alzheimer’s dementia.

The reviewers concluded that these therapies, which work to reduce amyloid-beta buildup in the brain, provide little to no measurable benefit for patients.

“Unfortunately, the evidence suggests that these drugs make no meaningful difference to patients,” said lead author Francesco Nonino, a neurologist and epidemiologist at the IRCCS Institute of Neurological Sciences of Bologna in Italy.

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Nonino added that while certain early trials showed statistically significant changes, those effects did not translate into clinical improvement.

“It is common for trials to find statistically significant results that do not translate into a meaningful clinical difference for patients,” he explained.

The review also flagged potential safety issues, including increased risks of swelling and bleeding in the brain.

In many cases, these issues appeared only on brain scans and did not cause noticeable symptoms, though researchers noted gaps in symptom data and unclear long-term effects.

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Based on the findings, the authors concluded that amyloid reduction by itself is unlikely to produce meaningful gains in memory or function. They argued that future research should consider alternative approaches beyond amyloid removal.

Senior author Edo Richard, professor of neurology at Radboud University Medical Centre, said the need for better treatments remains urgent.

“Existing approved drugs offer some benefit for some patients, but there remains a high unmet need for more effective treatments,” he noted.

However, the review’s publication quickly drew criticism from the Alzheimer’s Association and pharmaceutical companies behind existing therapies.

The nonprofit demanded Cochrane retract the paper, calling it “scientifically flawed” and warning that it could mislead patients and physicians alike.

“Many people living with mild cognitive impairment and mild dementia due to Alzheimer’s disease who are using these treatments are taking trips they weren’t sure they’d take, spending joyful time with friends and family, making plans for next month, doing things they love, and staying present in their lives,” the Alzheimer’s Association said in a statement.

The group argued that real-world data show similar benefits to those found in phase 3 trials, citing “clinically meaningful slowing of disease progression or cognitive decline with modest side effects.”

Lilly, the maker of donanemab, agreed with that assessment and called the Cochrane analysis “inherently flawed.” The company said combining results from both successful and failed drugs distorted the picture and failed to reflect the merits of individual therapies evaluated independently by regulators.

“Combining data on unsuccessful molecules with approved medicines artificially dilutes the observed benefit and produces class-level conclusions that do not reflect the evidence for any individual approved therapy,” a Lilly spokesperson said.

Leqembi, another amyloid-targeting drug developed by Eisai and Biogen, was approved by the Food and Drug Administration in early 2023.

Eisai defended its therapy as part of a new generation of treatments informed by previous failures and backed by long-term clinical data.

“The FDA has stated that lecanemab is part of a newer generation of anti-amyloid therapies targeting aggregated amyloid and has learned from previous failures,” the company said in a statement. “Extensive long-term clinical data out to four years and real-world experience with tens of thousands of patients globally show that patients who receive lecanemab continue to benefit from treatment.”

The Cochrane researchers acknowledged several limitations of their study, including variability between trials and the possibility that benefits differ among drugs or subgroups.

They also noted that follow-up periods might have been too short to capture long-term results.

Despite the pushback, the authors maintained that clinical outcomes should guide treatment decisions more than biomarker changes.

They emphasized, “Real-world data, along with clinical trial results, should guide decision-making.”

The divide underscores the ongoing challenge in Alzheimer’s research, where decades of amyloid-targeted efforts have yet to deliver a clear consensus on what truly slows or stops the disease’s devastating course.

For now, both sides agree on at least one point: patients need better answers, and the search for genuinely effective treatments must continue.