On June 7, 2021, the U.S. Food and Drug Administration (FDA) approved aducanumab, an amyloid beta-directed monoclonal antibody, as a new treatment for Alzheimer's disease (AD),1 taking advantage of Accelerated Approval program. The aducanumab effect on beta plaques2 was deemed to predict benefits patients and, thus, considered approvable surrogate endpoint. Nevertheless, there are residual unce...