Why The First Approved Alzheimer’s Drug In 17 Years Is Getting Mixed Reactions

It should be a cause for celebration: for the first time in 17 years, the US Food and Drug Administration has approved a drug for the treatment of Alzheimer’s disease – a monoclonal antibody named Aducanumab. Yet responses to the drug’s approval have varied, with some lauding it as an important step forward in the fight against Alzheimer’s, while others worry that it does nothing but give ‘false hope’ to sufferers. Why the controversy?

Aducanumab is an antibody, just like those produced by our B cells in response to a pathogenic infection. Instead of targeting antigens on the surface of pathogens, aducanumab targets and binds to amyloid beta aggregates, which are thought to play a role in Alzheimer’s disease, and helps the body to remove them from the brain. Phase I clinical trials were promising, suggesting that monthly infusions of the drug were effective in clearing amyloid from the brains of patients in the early stages of Alzheimer’s disease. However, two subsequent phase III trials found that Aducanumab did not sufficiently improve recipients’ cognitive function to merit further pursuit, and trials were dropped in 2019.

That would have been the end of Aducanumab: yet another Alzheimer’s drug that showed initial promise but that ultimately failed to deliver benefits for patients. However, half a year later, the companies developing the drug (Biogen and Eisai) changed their minds: they would seek approval for Aducanumab. Following a re-analysis of the data, they decided that the highest dose did yield meaningful benefits in some patients, including improved cognitive function. The FDA has now approved Aducanumab, though only for early-stage Alzheimer’s patients who have had a PET scan confirming the presence of beta-amyloid in their brains. The approval also comes with a stipulation: the companies will need to continue to test and demonstrate clinical benefit in order to keep the drug on the market.

For some, this represents a concerning departure from regulatory precedent. Only one of the two phase III trials showed benefits, and Aducanumab arguably does not meet the FDA’s standards for approval for other drugs. Yet because Aducanumab is a drug for a disease that currently has no treatment, the FDA decided that approving it anyway was justifiable. This sets a new precedent for treatments with considerable potential but unproven benefits to be approved on a conditional basis. Whether this is a good thing or not is up for debate, but many wanted to see more convincing evidence before approval, and worry that this development will give false hope to Alzheimer’s sufferers. On the other hand, the FDA rejected six amyloid-targeting drugs between 2016 and 2019, which arguably discouraged companies from pursuing Alzheimer’s treatments. The approval of Aducanumab may help encourage more much-needed innovation in this area.