How did the FDA advisory committee vote on aducanumab in June 2021 and what followed?

1. What people claimed — the competing, concise claims that matter

Multiple contemporaneous and retrospective accounts converge on two core claims: the advisory committee voted overwhelmingly against aducanumab’s approval, and the FDA approved the drug shortly afterward via accelerated approval. Some summaries state the committee voted 8–1–2 on specific questions about trial evidence (eight “no,” one “yes,” two “uncertain” on efficacy of the two pivotal trials), while others summarize the committee as voting 10–0 against approval with one abstention on the question of overall benefit; both formulations emphasize an overwhelming negative advisory view ^{[1] [2]}. Sources further claim that despite that negative advisory outcome, the FDA granted accelerated approval in early June or July 2021, relying on amyloid reduction as a surrogate endpoint—a decision that produced immediate institutional and public controversy ^{[3] [4]}. These competing numeric tallies reflect slightly different questions asked of the panel and differing ways journalists summarized the votes, but the shared fact is the advisory panel did not support approval while the agency approved the drug ^{[1] [3]}.

2. What the advisory committee actually voted—reconciling the numbers and questions

Detailed reporting shows the advisory committee’s negative conclusion depends on which specific ballot question is counted. On the critical question about whether two phase‑3 trials provided strong evidence of efficacy, reports record 8 votes “no,” 1 “yes,” and 2 “uncertain” in some accounts; other summaries compress later votes and abstentions into a “10–0 with one abstention” shorthand for the panel’s rejection of traditional approval ^{[1] [2]}. The panel did record some positive votes on narrower scientific points—five members said aducanumab had a pharmacodynamic effect on amyloid—yet these narrower acknowledgements did not translate into support for clinical benefit ^[1]. The numeric inconsistencies stem from panels answering multiple distinct questions during the meeting; journalists and institutions then paraphrased different votes, creating divergent headlines while preserving the core finding: an advisory body largely unconvinced of robust clinical benefit ^{[1] [2]}.

3. What the FDA did next—and when—supported by the record

Despite the advisory panel’s negative recommendation, the FDA granted accelerated approval for aducanumab in June/July 2021, invoking amyloid plaque reduction as a surrogate endpoint “reasonably likely” to predict clinical benefit. That regulatory move is documented in multiple analyses and retrospectives and is the pivotal post‑vote action that generated institutional fallout ^{[3] [4]}. Reports note the accelerated approval pathway and the timing—approval announced in early June but often referenced as a July administrative action in summaries—are central to understanding the sequence: advisory committee recommendation against traditional approval, then agency decision to approve under an expedited pathway ^[3]. The FDA’s choice to approve despite panel caution became a case study in regulatory discretion and set off immediate scrutiny of the agency’s processes ^[2].

4. Immediate reactions, resignations, and payer responses—how the fallout unfolded

The FDA’s decision prompted strong reactions: at least three advisory panel members publicly resigned or expressed dismay after the agency’s accelerated approval, citing concerns about the scientific basis for approval and the integrity of advisory processes ^[5]. Advocacy groups, scientists, and lawmakers criticized the FDA for departing from its panel’s advice, calling for reform; at the same time some patients and caregivers welcomed a new therapeutic option. Payer responses were swift and consequential: in April 2022 Medicare limited coverage of aducanumab to patients enrolled in clinical trials, and many private insurers followed with restrictive policies—moves that dramatically curtailed real‑world access and reimbursement despite approval ^{[6] [3]}. These downstream policy choices underscore how regulatory approval does not automatically equate to broad clinical uptake or endorsement by payers ^[6].

5. Why sources differ—and what agendas or framing to watch for

Differences in vote totals, dates, and emphasis reflect source aims and the specific questions reporters emphasized. Trade and advocacy outlets emphasize patient access and the accelerated pathway’s potential benefits; clinical and policy analyses emphasize methodological shortcomings in Biogen’s data and the perceived weakening of advisory influence ^{[6] [3]}. Retrospectives written later sometimes compress the timeline or reframe the vote totals to underline calls for FDA structural reform, while contemporaneous reporting often highlighted raw panel vote counts and immediate resignations ^{[1] [2]}. Readers should watch for framing that either amplifies patient‑access arguments or emphasizes regulatory failure—both frames are present in the record and influence how the same facts are presented ^{[6] [5]}.

6. Bottom line and lasting context—what this episode changed

The enduring facts are clear: an FDA advisory committee almost uniformly rejected the evidence for aducanumab’s clinical benefit, the FDA nonetheless granted accelerated approval based on a surrogate endpoint, and that choice produced resignations, payer restrictions, and broader scrutiny of FDA decision‑making. Subsequent developments—Medicare coverage limits, litigation, and Biogen’s later strategic shifts—show the approval’s practical impact was more limited than an unconditional endorsement would suggest ^{[6] [3]}. The episode reshaped debate over the balance between expedited access and evidentiary standards, and it remains a touchstone for proposals to reform advisory processes and surrogate‑endpoint approvals ^[4].