European committee says Alzheimer's treatment Leqembi shouldn't get marketing approval

Shares of Biogen slid Friday after a European regulatory committee said the Alzheimer’s treatment Leqembi should not receive marketing approval.

The European Medicines Agency committee said concerns about the drug’s potential side effects outweigh the impact it has in slowing the fatal, mind-robbing disease.

Japanese drugmaker Eisai developed Leqembi and is co-marketing it with Cambridge, Massachusetts-based Biogen Inc. An Eisai executive said in a statement that company officials were “extremely disappointed,” and they will ask for a re-examination of the decision.

The European Committee for Medicinal Products for Human Use recommended 14 new medicines for approval at its July meeting. Leqembi was the only one to receive a negative opinion.

The treatment already has received approval in the United States, Japan, China, South Korea, Hong Kong and Israel.

Leqembi clears a sticky brain plaque linked to the disease. A large study has shown that it slowed memory and thinking decline by several months in those who received the treatment compared to those who got a dummy drug.

But it also can cause brain swelling and bleeding, side effects that can be dangerous in rare cases.

TD Cowen analyst Phil Nadeau said in a note that he was surprised and disappointed by the committee decision. But he said it does not affect his sales estimates because he assumed any European launch “would be very slow as reimbursement was negotiated and the complicated logistics of diagnosis and treatment were worked out.”

Leqembi received full approval last year from the U.S. Food and Drug Administration. Earlier this month, the FDA also approved another drug that takes a similar approach, Eli Lilly’s Kisunla.

Biogen's stock fell more than 4% to $216.82 after markets opened Friday, and Lilly shares slipped 1%. The Standard & Poor's 500 index climbed nearly 1% at the start of trading.