Aduhelm FDA Approval: Controversy, Medicare Block, and Discontinuation

The Aduhelm FDA approval controversy centers on the agency’s June 7, 2021 decision to clear the Alzheimer’s drug aducanumab through its accelerated approval pathway despite unanimous opposition from its own advisory committee, thin and conflicting trial evidence, a $56,000 annual price tag, and a surrogate endpoint that critics said had never been shown to predict real cognitive benefit.¹ Medicare then restricted coverage so tightly that the drug barely reached patients, Congress investigated the FDA’s conduct, and Biogen discontinued Aduhelm on January 31, 2024, without ever completing the confirmatory trial the approval had required.²

An Advisory Committee That Voted No

The FDA’s Peripheral and Central Nervous System Drugs Advisory Committee reviewed Aduhelm before the approval decision. Not a single member voted to recommend approval.³ The FDA’s own statistical reviewers also concluded the evidence did not support approval.⁴

When the agency approved the drug anyway, three committee members resigned: Dr. Aaron Kesselheim, Dr. David Knopman, and Dr. Joel Perlmutter. An override of a unanimous negative vote is extraordinarily rare, and the resignations put the disagreement squarely in public view.

The initial label added to the concern. The FDA authorized Aduhelm broadly for Alzheimer’s disease, without limiting it to the early-stage patients who had actually been studied. The label was later revised to specify that treatment should begin in patients with mild cognitive impairment or mild dementia.⁵

Two Trials, One Halted for Futility, and a Reversal

The scientific case rested on two identical Phase 3 trials, EMERGE and ENGAGE. In March 2019, an independent data monitoring committee reviewed interim results and concluded both trials were unlikely to meet their primary endpoints. Biogen halted them.⁴

A later analysis of a larger dataset produced a different picture. Biogen announced that the high-dose arm of EMERGE had shown a statistically significant slowing of cognitive decline. ENGAGE still failed. The company attributed the split to differences in how much drug patients had received before the trials were stopped. Critics saw one positive trial and one negative trial, both halted early for futility, and said that was not reliable evidence of benefit.

The Accelerated Approval Pathway and the Surrogate Endpoint Question

The FDA cleared Aduhelm under the Accelerated Approval pathway in 21 U.S.C. § 356, which allows approval of drugs for serious conditions based on a surrogate endpoint reasonably likely to predict clinical benefit, rather than direct proof that patients feel or function better.⁶ In exchange for the faster route, the manufacturer must run a confirmatory trial afterward, and the FDA can withdraw approval if that trial fails.⁷

For Aduhelm, the surrogate was reduction of amyloid-beta plaques in the brain. The pathway had a strong track record in oncology and HIV, where surrogates like tumor shrinkage and viral load had reliably tracked with clinical outcomes. Amyloid clearance was different. The plaque theory of Alzheimer’s is longstanding, but the Aduhelm trials never clearly connected plaque removal to cognitive improvement, which is what made the surrogate choice contested.

Price and Safety

Biogen set Aduhelm’s initial wholesale acquisition cost at roughly $56,000 per year. For a drug with uncertain benefit, the number drew immediate criticism from physicians, patient advocates, and policymakers. In December 2021, Biogen cut the price roughly in half, to $28,200 per year for a patient of average weight.⁸ By that point the drug’s commercial trajectory had already collapsed.

The main safety concern was Amyloid-Related Imaging Abnormalities, or ARIA, which appear on MRI as brain swelling (ARIA-E) or small brain bleeds (ARIA-H). Across anti-amyloid antibody trials, ARIA-E occurred in about 13% to 35% of patients, with symptomatic cases in 3% to 9%, and ARIA-H in 14% to 27%. Most cases resolved, but the condition required ongoing MRI monitoring, which added cost and logistical strain for elderly patients and their caregivers.

Why Medicare Blocked Routine Access

Most Alzheimer’s patients are on Medicare, so what CMS decided about coverage mattered as much as what the FDA had done. Through a National Coverage Determination, CMS restricted Medicare coverage of anti-amyloid monoclonal antibodies approved on a surrogate endpoint to patients enrolled in qualifying randomized controlled trials conducted under an FDA investigational new drug application.⁹ This framework, called Coverage with Evidence Development, meant physicians could not simply write a prescription for a Medicare patient. They had to enroll the patient in an approved study.¹⁰

For an elderly, cognitively impaired population, that hurdle was near-impossible in ordinary clinical settings. The NCD created a two-track system: drugs approved on surrogate endpoints faced the strict trial requirement, while drugs that later earned traditional FDA approval based on direct clinical benefit could be covered through less restrictive registry-based studies. Aduhelm never crossed to the second track.

What Congress and the Inspector General Found

In December 2022, the House Committees on Oversight and Energy and Commerce released a staff report on the review, approval, and pricing of Aduhelm.¹¹ The report documented at least 115 meetings, calls, and substantive email exchanges between the FDA and Biogen over a 12-month period starting in July 2019, plus 66 additional contacts that were not properly documented. It found that the FDA and Biogen had collaborated on a joint briefing document for the advisory committee, a practice an internal FDA review later called inappropriate because it gave the company advance insight into the agency’s thinking. The report also noted that the FDA had reviewed Aduhelm under the traditional approval pathway for nine months before switching to accelerated approval and completing that review in three weeks.

The HHS Office of Inspector General examined the accelerated approval pathway more broadly and flagged concerns in 3 of 24 drugs reviewed, Aduhelm among them. The OIG recommended that the FDA define factors requiring its accelerated approval council to weigh in on certain applications and that it improve documentation of meetings with drug sponsors. The FDA concurred with the documentation recommendation and disagreed with the first.¹²

Discontinuation in 2024

On January 31, 2024, Biogen announced it would end development and commercialization of Aduhelm and terminate ENVISION, the Phase 4 confirmatory trial the FDA had required as a condition of accelerated approval.² The company framed the move as a reallocation toward Leqembi (lecanemab), which it had developed with Eisai. Patients still receiving Aduhelm were given until November 1, 2024, for their final infusions. Without a completed confirmatory trial, the accelerated approval was never converted to traditional approval, and Aduhelm exited the U.S. market.

What the Episode Changed

Two successor anti-amyloid antibodies reached patients with stronger regulatory footing. Leqembi received traditional FDA approval on July 6, 2023, based on the Phase 3 CLARITY AD trial, which showed roughly a 27% slowing of cognitive decline over 18 months.¹³¹⁴ Because that approval was based on direct clinical benefit rather than a surrogate, CMS granted broader Medicare coverage, requiring only that physicians participate in a data registry.¹⁵ Kisunla (donanemab) followed on July 2, 2024.¹⁶ Both carry ARIA risks similar to Aduhelm’s and require MRI monitoring.

Congress also acted. The FDORA Act of 2022 gave the FDA streamlined authority to withdraw accelerated approvals when confirmatory trials fail or are not completed.⁶ The prior withdrawal process required a lengthy administrative hearing the agency had almost never used, which was part of why an approval like Aduhelm’s had proved so hard to reverse quickly. The Aduhelm story reads as a case study in what happens when a surrogate endpoint stretches past what its evidence supports, a review process bends around a single sponsor, and the payer that covers most affected patients decides the answer separately from the FDA.

1
Food and Drug Administration. FDA Approval Letter for Aduhelm (BLA 761178)
2
Biogen. Biogen to Realign Resources for Alzheimer’s Disease Franchise
3
PubMed Central. Revisiting FDA Approval of Aducanumab
4
PubMed Central. ENGAGE and EMERGE: Truth and Consequences?
5
Food and Drug Administration. Aduhelm Prescribing Information (Revised 2023)
6
Office of the Law Revision Counsel. 21 USC 356 – Expedited Approval of Drugs for Serious or Life-Threatening Diseases or Conditions
7
eCFR. 21 CFR Part 314 Subpart H – Accelerated Approval of New Drugs for Serious or Life-Threatening Illnesses
8
Biogen. Biogen Announces Reduced Price for ADUHELM to Improve Access for Patients with Early Alzheimer’s Disease
9
Centers for Medicare & Medicaid Services. National Coverage Determination 200.3 – Monoclonal Antibodies Directed Against Amyloid for the Treatment of Alzheimer’s Disease
10
Centers for Medicare & Medicaid Services. Monoclonal Antibodies Directed Against Amyloid for the Treatment of Alzheimer’s Disease – Decision Memo
11
The U.S. House Committee on Oversight. Maloney and Pallone Release Staff Report on Review, Approval, and Pricing of Biogen’s Alzheimer’s Drug Aduhelm
12
Office of Inspector General. How FDA Used Its Accelerated Approval Pathway Raised Concerns in 3 of 24 Drugs Reviewed
13
Food and Drug Administration. FDA Converts Novel Alzheimer’s Disease Treatment to Traditional Approval
14
New England Journal of Medicine. Lecanemab in Early Alzheimer’s Disease
15
Centers for Medicare & Medicaid Services. Broader Medicare Coverage of Leqembi Available Following FDA Traditional Approval
16
Food and Drug Administration. FDA Roundup: July 2, 2024