Biogen and Eisai's Alzheimer's treatment Leqembi is rejected by the European drug regulator.

• The rejection of Alzheimer's treatment Leqembi by European drug regulators has added another obstacle for Biogen and Eisai in their efforts to increase its usage in the U.S.
• The EU's executive body, the European Commission, usually agrees with the drug regulator's recommendations.
• The regulator stated that the potential risks associated with Leqembi outweigh its benefits in delaying cognitive decline.

On Friday, European drug regulators rejected Leqembi as an Alzheimer's treatment for both the UK and France, adding another obstacle for the companies in increasing the therapy's uptake in the US.

The European Commission, as the EU's executive body, typically approves drugs based on the recommendations of the drug regulator.

Eisai expressed "extreme disappointment" over the regulator's negative recommendation and stated that it will seek a re-examination of the decision.

Nearly 7% of Biogen's shares fell in premarket trading on Friday, while Eisai's stock remained relatively unchanged.

Despite regulatory approvals in several countries, including Japan, South Korea, China, and Israel, the U.S. Food and Drug Administration's approval of Leqembi has seen a slow rollout due to diagnostic test requirements and regular brain scans, among other issues.

The monoclonal antibody drug has been hailed as a breakthrough for a difficult-to-treat progressive disease, as it slows the disease's progression in early-stage patients.

The European Medicines Agency's human medicines committee advised against approving marketing authorization for Leqembi.

The committee concluded that the benefits of Leqembi in slowing cognitive decline do not justify the "high risk of severe side effects," including frequent brain swelling and bleeding, associated with the medication.

The drugs Leqembi and Kisunla, which target and clear a toxic plaque in the brain called amyloid, are associated with side effects. Kisunla was recently approved in the U.S.

After three decades of unsuccessful attempts to develop medicines for Alzheimer's, Leqembi and Kisunla have emerged as promising milestones in the treatment of the disease.

In 2021, the European Medicines Agency rejected Aduhelm, another ill-fated drug from Biogen and Eisai that struggled to gain traction in the U.S. after questions about its approval and data.

By 2050, the number of people in Europe with Alzheimer's disease is predicted to double, reaching a total of 14 million, according to data from Alzheimer's Europe.