WASHINGTON (NEWSnet/AP) — An experimental Alzheimer’s drug can slow a patient’s decline by about four to seven months, researchers said Monday.

Eli Lilly and Co. seeks approval from U.S. Food and Drug Administration for donanemab. If cleared, it would be only the second Alzheimer’s treatment convincingly shown to delay the disease. Leqembi, by Japan drugmaker Eisai, is the first.

Result of a study of 1,700 patients was published Monday by Journal of the American Medical Association and presented at the conference.

Donanemab and Leqembi are lab-made antibodies, administered by IV, that target one Alzheimer’s culprit, sticky amyloid buildup in the brain. Both drugs come with a major safety concern: brain swelling or bleeding. In the Lilly study, that was linked to three deaths.

Scientists said these drugs may mark a new era in Alzheimer’s therapy, but questions remain about which patients should try them and how much benefit they’ll notice.

Lilly’s study enrolled people ages 60 to 85 in early stages of Alzheimer’s. Half received a once-per-month infusion of donanemab and half got a dummy infusion for 18 months.

Patients were switched to dummy infusions if enough amyloid was cleared, which was the case for about half in the study. Because amyloid alone doesn’t cause Alzheimer’s, researchers also tracked levels of another culprit in the brain, abnormal tau. More tau signals more advanced disease.

Both groups declined during the 18-month study, but overall those given donanemab did so about 22% more slowly, in the range of four to seven months’ difference. Some patients fared better — those with low to medium tau levels had a 35% slower decline, suggesting the drug is more effective in earlier stages of the disease.

How much difference does that make? It means donanemab slowed patients’ worsening by about four to seven months, the JAMA report concluded.

About a quarter of donanemab recipients showed evidence of brain-swell, and about 20% had microbleeds. Scientists already know that patients getting any amyloid-targeted therapy need repeat brain scans to check for those side effects — a costly and time-consuming hurdle.

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