Regulatory decisions diverge over aducanumab for Alzheimer’s disease

The European Medicines Agency refused marketing authorisation for aducanumab (Aduhelm), a monoclonal antibody targeted at amyloid β, in December 2021. It noted that “although Aduhelm reduces amyloid beta in the brain, the link between this effect and clinical improvement had not been established.”1 Furthermore, it concluded “studies did not show that the medicine was sufficiently safe,” citing reported side effects including brain swelling and bleeding. This decision contrasts with that of the US Food and Drug Administration, which granted the drug accelerated approval in June 2021.2

The FDA’s approval of aducanumab for treatment of Alzheimer’s disease was based on a reduction in amyloid β plaques during clinical trials. Reduction in plaque levels is not a clinical endpoint, however, and the drug’s manufacturer, Biogen, is required to complete post authorisation trials evaluating true clinical benefit.

This FDA approval has been one of the most consequential and controversial regulatory decisions in recent years.3 The FDA’s peripheral and central nervous system drugs advisory committee voted almost unanimously against approval, and three …