Benefit of Eisai and Biogen's Alzheimer's drug increases over time, studies suggest

By Julie Steenhuysen

CHICAGO (Reuters) - The benefit of Eisai and Biogen's Alzheimer's drug Leqembi in patients with early-stage Alzheimer's appears to increase with continued use with no new safety issues, according to three-year data presented at an Alzheimer's meeting on Tuesday.

In the companies' pivotal clinical trial, Leqembi reduced cognitive decline by 27% after 18 months - data that supported the drug's approval last year.

The new study looked at how the drug performed in about 95% of trial patients who continued on the treatment. After three years, Leqembi 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, Dr. Christopher van Dyck, director of the 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 showed 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 continues to benefit patients who stay on Leqembi 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. Leqembi 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," Dr. Lynn Kramer, Eisai's chief clinical officer, told Reuters.

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

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

(Reporting by Julie Steenhuysen; Editing by Bill Berkrot)