An international phase 3 study of Eli Lilly’s Alzheimer’s drug donanemab found that it slowed cognitive decline by 35% in people diagnosed at an early stage of the disease, according to Reuters. Researchers said the treatment’s benefits continued to be observed for 18 months after therapy began.

The trial adds to growing evidence that amyloid-targeting medicines may help delay symptom progression for some patients, though the therapy does not stop or reverse Alzheimer’s. The findings are likely to renew debate over how widely such treatments should be used, given questions about cost, access, and safety monitoring.

Donanemab is part of a new class of drugs aimed at removing amyloid plaques from the brain, one of the biological hallmarks associated with Alzheimer’s disease. The latest results suggest that earlier diagnosis and treatment may be key to getting the most benefit from the drug.

While the results represent a meaningful step for patients and families facing the disease, experts caution that the gains are modest and the therapy will still require careful medical oversight. Further real-world data will help determine how the drug performs outside tightly controlled clinical trials.