Biogen's Aduhelm (aducanumab)
The Alzheimer's drug approved against expert advice, priced at $56,000 and withdrawn
Aduhelm was the first drug approved in nearly two decades for Alzheimer's disease, and the first to target the amyloid plaques associated with it. Its June 2021 approval, however, became one of the most controversial decisions in the FDA's history. This article focuses on the drug itself: the conflicting trial data, the approval pathway, safety, pricing, coverage and the congressional findings.
Questions
What was Aduhelm and why was its approval such a big deal?
A monoclonal antibody approved in June 2021 to clear amyloid plaques — over the objections of its outside advisers — opening a potential multibillion-dollar Alzheimer's market that one expert called the worst FDA decision ever made.
Aduhelm (aducanumab) was a monoclonal antibody given by monthly infusion, designed to clear amyloid-beta plaques from the brain. The FDA granted it accelerated approval on June 7, 2021 on the basis that it reduced amyloid, a surrogate marker, rather than on proof it slowed cognitive decline. With more than six million Americans living with Alzheimer's, the approval promised a new era for patients and a potentially enormous market for Biogen. But it came over the objections of the FDA's outside advisers, who did not believe the data definitively proved benefit, and one expert described it as "the worst decision the FDA has ever made". The drug's short commercial life and eventual discontinuation reflect how contested it was.
Q2Why were Aduhelm's clinical trial results considered unreliable?
Both phase 3 trials were stopped as futile in March 2019; Biogen later reanalysed a larger dataset and found benefit in only one trial. The FDA's own statistical team said the evidence was insufficient — so the agency approved on the surrogate endpoint instead.
Biogen ran two large phase 3 trials, EMERGE and ENGAGE. In March 2019, Biogen cancelled both trials after an independent analysis concluded the drug was unlikely to slow cognitive and functional decline and that further study would be futile. Later that year Biogen reanalysed a larger dataset and argued that the high dose showed benefit in EMERGE, although ENGAGE remained negative. Having one positive and one negative trial, with the positive result emerging only after a futility stop, is a weak evidentiary basis. The FDA's own statistical team argued there was insufficient evidence of Aduhelm's benefits. The agency's decision to approve on amyloid reduction, rather than on the disputed clinical endpoints, effectively sidestepped this problem, which critics argued undermined the purpose of requiring confirmatory evidence.
Q3How did Aduhelm switch to the accelerated approval pathway?
After a November 2020 advisory meeting went badly, the FDA pivoted to accelerated approval on amyloid reduction — contrary to its own Alzheimer's guidance — a move the congressional investigation called abrupt and irregular.
Biogen originally sought traditional approval based on clinical benefit. After the November 2020 advisory committee meeting went badly, the FDA pivoted. The congressional report found Aduhelm "abruptly" gained accelerated approval after unfavourable feedback from the advisory committee through the traditional process, and that this was contrary to the FDA's own guidance for Alzheimer's drugs. Accelerated approval allows the FDA to approve drugs for serious conditions based on a surrogate endpoint "reasonably likely" to predict clinical benefit, on condition that confirmatory trials follow. Critics argued amyloid reduction had not been shown to predict benefit, since previous amyloid drugs had failed despite reducing plaques. The FDA said it would continue to use accelerated approval whenever appropriate, and the pathway remains in use.
Q4What was wrong with Aduhelm's label?
The FDA initially approved Aduhelm for all Alzheimer's disease, despite trials limited to mild-stage patients — a broad label that inflated market potential and Medicare exposure before being narrowed just one month later.
The FDA initially approved Aduhelm for Alzheimer's disease broadly, without limiting it to the early-stage patients who were actually studied. The congressional investigation found the FDA accepted a broad label indication despite a lack of clinical data on disease stages other than mild cognitive impairment and mild Alzheimer's, and that Biogen accepted the broad label despite internal reservations. On July 9, 2021, only a month later, the FDA narrowed the label to patients with mild cognitive impairment or mild dementia, and the same day called for a federal investigation into the approval. A broad label matters because it expands the potential market, which in turn influences pricing, Medicare budgeting and premiums.
Q5What were Aduhelm's safety risks?
About 41% of patients on the high dose experienced amyloid-related imaging abnormalities including brain swelling in 35% — all requiring repeated MRI monitoring — while uncertain benefit left many reviewers concluding the risk profile was hard to justify.
The main risk was amyloid-related imaging abnormalities, or ARIA, which includes brain swelling and small bleeds visible on MRI. A secondary analysis of the phase 3 trials published in JAMA Neurology found that about 41% of patients on the high dose experienced ARIA, with brain swelling (ARIA-edema) affecting 35%. About a quarter of those with ARIA-edema had symptoms, most commonly headache, confusion, dizziness and nausea, and microhaemorrhages affected about 19%. Because ARIA requires regular MRI monitoring, the drug's real cost included scans and specialist visits on top of the infusion. Medicare cited the potential for harm when restricting coverage. Supporters noted most ARIA was asymptomatic and resolved, but the risk profile, combined with uncertain benefit, weighed heavily in the backlash.
Q6How was Aduhelm priced and why was that controversial?
Biogen launched at $56,000 — when ICER said $3,000–$8,400 would be cost-effective — because internal documents show it saw Aduhelm as an unprecedented financial opportunity, planning $3.3 billion in marketing spend from 2020 to 2024.
Biogen set a list price of $56,000 a year, well above the $10,000 to $30,000 many industry watchers had expected. ICER said a cost-effective price would be $3,000 to $8,400 a year. The congressional investigation concluded Biogen set an unjustifiably high price to "make history", seeing the drug as an unprecedented financial opportunity, and found Biogen knew from early pricing models that some Medicare patients would struggle to afford it. In December 2021, facing weak uptake and payer resistance, Biogen cut the price to $28,200, a 50.3% reduction and an unusual move for a drugmaker. Even the reduced price was well above ICER's recommended range of $2,500 to $8,000. Biogen simultaneously announced $500 million in cost cuts.
Q7How did Aduhelm affect Medicare and its beneficiaries?
CMS projected a 15% rise in 2022 Part B premiums citing Aduhelm as the main reason — meaning 50 million beneficiaries paid more in anticipation of a drug very few would use, and mid-year corrections were legally impossible.
Because Aduhelm is infused in clinics, it falls under Medicare Part B, which is partly funded by premiums paid by all beneficiaries. For 2022, CMS projected a 15% increase in Part B premiums and cited potential coverage of Aduhelm as the main reason. HHS Secretary Xavier Becerra ordered CMS to reassess the premium after the price cut, but legal and operational hurdles prevented mid-year changes, and the savings were rolled into 2023 premiums. In April 2022 Medicare finalised a narrow national coverage determination limiting payment to patients in qualifying clinical trials. The result was that the more than 50 million Americans who pay Part B premiums paid higher premiums in 2022 in anticipation of spending on a drug that very few would use.
Q8What did Congress find about the relationship between Biogen and the FDA?
FDA staff and Biogen had at least 115 informal exchanges over 12 months, jointly prepared a briefing document for the advisory committee, and Biogen planned to spend more than $3.3 billion marketing Aduhelm — findings the FDA's own internal review called atypical.
The House Oversight and Energy and Commerce committees' 18-month investigation found that FDA staff and Biogen had at least 115 meetings, calls and substantive email exchanges over 12 months beginning July 2019, many not properly documented. The two jointly prepared a briefing document for the advisory committee, which the report said gave Biogen advance insight into the FDA's responses. The FDA's own internal review had found the collaboration atypical and exceeding the norm in some respects. The committees also disclosed Biogen's plan to spend more than $3.3 billion marketing Aduhelm from 2020 to 2024. Biogen said it stood by the integrity of its actions, and FDA Commissioner Robert Califf remarked there were "no surprises in the report".
Q9What happened to Aduhelm in the end?
Biogen discontinued Aduhelm on January 31, 2024 — after Medicare restricted coverage to trials, major health systems refused to stock it and European regulators rejected it — redirecting resources to lecanemab developed with Eisai.
Adoption never took off. Several major health systems declined to use it, most payers held off coverage, Medicare restricted payment to trials, and the European Medicines Agency refused to authorise it. On January 31, 2024 Biogen announced it was discontinuing Aduhelm, ending trials by May 2024 and supply to existing patients by November 2024, and redirecting resources to lecanemab, developed with Eisai. The Alzheimer's Association credited Aduhelm with opening a new era of anti-amyloid treatments. Critics saw the episode as a textbook case of overpromising and under-delivering, and as evidence of the risks of approving drugs on surrogate markers without solid clinical evidence, particularly when the price and potential patient population are both very large.
Q10How did doctors, health systems and insurers respond to Aduhelm?
The Cleveland Clinic, the VA and most major private insurers declined to offer or cover it. Infusion infrastructure costs added to the burden, and six months after launch most payers had still not committed to coverage — a primary reason for the drug's commercial failure.
Many turned away from it. Several major health systems, including the Cleveland Clinic and the Department of Veterans Affairs, declined to offer Aduhelm to patients after approval. Most major private insurers waited for Medicare's coverage decision before deciding whether to cover it, and six months after launch most payers had decided not to cover it, at least for the time being. Medicare then restricted coverage to patients in approved trials. Because the drug required monthly infusions and repeated MRI monitoring for brain swelling, the infrastructure costs for clinics were also significant. The patient group UsAgainstAlzheimer's argued after the price cut that cost should now be off the table in Medicare's decision. The Alzheimer's Association later said Aduhelm's approval "provided hope for the millions of people living with early Alzheimer's" and began a new era of treatments. The limited uptake is a key reason Biogen ultimately discontinued the drug.
Q11What lessons have regulators and payers drawn from Aduhelm?
The FDA began implementing documentation reforms, CMS's restriction to clinical trials became a model for uncertain approvals, and Aduhelm now sits alongside Elevidys in debates about when surrogate endpoints are acceptable — showing how approval standards, pricing and Medicare financing are tightly connected.
The episode has had lasting effects. The FDA said it had begun implementing some of the congressional report's recommendations, including clearer documentation of interactions with drug sponsors. Public Citizen argued the FDA must ensure that future Alzheimer's reviews do not lead to the same doubts about integrity. CMS's use of coverage restricted to clinical trials became a model for handling costly drugs with uncertain benefit. The Aduhelm saga also informed debates that later surrounded other accelerated approvals, such as Sarepta's Elevidys, where senior officials likewise overruled review staff. The central lesson most observers draw is that approval standards, pricing and Medicare financing are tightly connected, and weakness in one can raise costs across the whole system.