The landmark accelerated approval of Biogen and Eisai’s anti-amyloid antibody Aduhelm (aducanumab) came despite Phase III clinical trial data resulting in one positive and one negative study. In its release of this groundbreaking news, the US Food and Drug Administration (FDA) acknowledged there was some uncertainty around the data, but reiterated that the treatment was the first to show a benefit in amyloid plaque reduction, thus targeting the underlying disease pathology rather than masking symptoms. Due to the controversy surrounding Aduhelm’s approval and launch leading to much lower sales than had been expected, the drug has since been withdrawn from the market. 

The FDA’s accelerated approval of Aduhelm based on amyloid reduction rather than cognitive improvement lowered the bar for approval, though market access barriers remain. Medicare will cover about 80% of the cost of anti-amyloid antibodies, and the Centers for Medicare & Medicaid Services will only cover drugs using the accelerated approval pathway under an FDA-approved randomized controlled trial that evaluates clinical benefit, severely limiting patient access. 

In July 2023, Leqembi (lecanemab) became the first anti-amyloid antibody to gain full approval from the FDA, after previously receiving accelerated approval from the agency in January 2023. A year later, Eli Lilly’s Kisunla (donanemab) gained a traditional approval after a receiving a positive endorsement from an advisory committee.