European watchdog partially approves new Alzheimer's drug

Europe's medicines watchdog on Thursday partially approved a marketing request for a long-awaited new treatment for Alzheimer's disease, reversing an earlier decision not to give it the green light.

"After re-examining its initial opinion, the EMA...has recommended granting marketing authorisation to Leqembi (lecanemab) for treating mild cognitive impairment or mild dementia due to Alzheimer's disease," the European Medicines Agency said, adding treatment would only apply to a certain group of patients.

Leqembi, which was developed by US multinational Biogen and Japanese-based Eisai, is the brand name of an active substance called lecanemab, which is used to treat adults with mild memory and cognitive problems resulting from the early stages of the common type of dementia.

The EMA in July rejected a marketing request by the companies, saying the side effects, including potential brain bleeding, outweighed the benefits.

The EMA now endorsed the treatment, but only for patients with a lower risk of potential brain bleeding — those who had "only one copy or no copy of ApoE4", a type of gene know as an important risk factor for Alzheimer's.

Such patients are less likely to experience certain serious health problems than people with two copies of the gene, the Amsterdam-based EMA said.

The health problems in question, known as amyloid-related imaging abnormalities (ARIA), include fluid on the brain and brain bleeding.