WASHINGTON D.C.: According to trial data contained in a report presented this week, an experimental Alzheimer's drug from Eisai and Biogen, lecanemab, slowed cognitive decline, but could cause serious side effects for certain patients.

In the 18-month trial involving nearly 1,800 participants with early-stage Alzheimer's, Lecanemab was possibly the cause of a dangerous type of brain swelling in nearly 13 percent of patients.

Five patients also suffered from macrohemorrhages and 14 percent from microhemorrhages, which could have caused two deaths in a follow-on study.

In September, the two companies said that lecanemab, an antibody designed to remove sticky deposits of a protein called amyloid beta, reduced the rate of cognitive decline on a clinical dementia scale (CDR-SB) by 27 percent, compared to a placebo.

However, Dr. Ronald Petersen of the Mayo Clinic in Rochester, Minnesota said, "All of these amyloid-lowering drugs carry a risk for increased brain hemorrhage."

The data confirms the drug "can meaningfully change the course of the disease," said the Alzheimer's Association, calling on U.S. regulators to approve the company's application for accelerated approval.

Detailed data from the study was presented at the Clinical Trials on Alzheimer's Disease meeting in San Francisco.

The U.S. Food and Drug Administration (FDA) will decide whether to approve lecanemab under its "accelerated" review program by 6th January. However, Eisai will soon file for standard FDA approval of the drug and will also seek approval in Europe and Japan, regardless of the FDA's decision.