The benefit of lecanemab in patients with early-stage Alzheimer's disease appears to increase with continued use with no new safety issues, according to three-year data presented at an Alzheimer's meeting.

In the companies' pivotal clinical trial, lecanemab reduced cognitive decline by 27% after 18 months - data that supported the drug's approval last year. The new study looked at the drug's performance in about 95% of trial patients who continued the treatment. After three years, lecanemab slowed cognitive decline by 31% compared to what would be expected in similar patients who did not receive treatment.

There were no new safety findings over the three-year period. Brain swelling and bleeding associated with drugs that work by removing amyloid plaque from the brain largely occurred within the first six months of treatment, Christopher van Dyck, MD, director of Yale's Alzheimer's Disease Research Unit, told the meeting.

A separate analysis of data from a midstage study looked at patients who had a gap in treatment of 9 to 59 months following 18 months of initial treatment. In that study, there was still a difference, but once treatment stopped, the rate of cognitive decline reverted back to what was seen in patients on placebo.

Discontinuation of treatment also led to increases in Alzheimer's-related disease biomarkers, such as the return of amyloid plaques. The findings were part of several presentations at the Alzheimer's Association International Conference in Philadelphia aimed at showing that Eisai's drug, lecanemab, continues to benefit patients who stay on the treatment after amyloid has been removed.

Eisai's drug targets protofibrils - toxic building blocks that eventually form clumps in the brain known as amyloid plaques, a hallmark of Alzheimer's disease. Lecanemab both removes amyloid plaques and continues to target protofibrils, which can injure brain cells.

"There is no question long-term benefit is better than short-term benefit," remarked Lynn Kramer, MD, Eisai's chief clinical officer.

The studies underline differences between Eisai and Biogen's treatment and Eli Lilly's Alzheimer's drug, donanemab, which was approved on July 2.

The Lilly drug exclusively targets amyloid plaques. Once the brain plaque is gone, patients can discontinue treatment.