The Third Field

Cases from the record · 2020 – 2024

Aduhelm at the FDA

The evidence was disputed. The route to approval changed.

An Alzheimer’s drug was approved after the FDA’s outside experts voted against the main evidence for it. The agency’s own records show where the disagreement went.

Process lens Proposals → Decide

10 of 11advisory committee members voted against the main evidence question; one was uncertain (FDA)
3committee members resigned after the approval (congressional staff report; HHS inspector general)
2029due date set at approval for the trial meant to confirm the benefit (FDA approval letter)

What happened

In July 2020 Biogen applied for approval of aducanumab, later sold as Aduhelm, for Alzheimer’s disease. In November 2020 the FDA’s outside advisory committee voted against treating the main trial as primary evidence that the drug worked.

In June 2021 the FDA approved it under accelerated approval, on the basis that it reduced amyloid plaque in the brain, with a confirmatory trial due by 2029. Three committee members resigned. Medicare later limited coverage to clinical trials, and in 2024 Biogen discontinued the drug. A congressional staff report and the HHS inspector general examined how the decision was reached.

  1. The application is submitted.

  2. The advisory committee votes 10 against, 1 uncertain, on whether the main trial can be primary evidence of effectiveness.

  3. After about nine months reviewing for traditional approval, the agency begins to consider accelerated approval.

  4. Aduhelm is approved under accelerated approval.

  5. Medicare covers drugs of this kind only within clinical trials.

  6. Staff of two House committees publish their investigation.

  7. Biogen announces it will discontinue Aduhelm.

What the record shows

  1. 01

    The experts were asked one question, not the other.

    The committee voted against treating the main trial as primary evidence. The inspector general found the FDA never asked it to vote on whether the application suited accelerated approval, the route it later used.

  2. 02

    The dissent was written down.

    The agency’s statistical review concluded that “substantial evidence has not been met.” The head of its biostatistics office, the congressional staff report records, judged the evidence insufficient for any type of approval.

  3. 03

    The route changed late.

    According to the staff report, the application was reviewed for traditional approval for about nine months; accelerated approval was considered seriously only after an internal meeting in April 2021.

  4. 04

    The disagreement stayed informal.

    The inspector general found the reviewers’ concerns were not resolved before approval. The staff report says the biostatistics team was not invited to later working-group meetings with the company.

  5. 05

    Unusually close contact.

    The staff report counts at least 115 meetings, calls and emails between the agency and the company over one year; the inspector general documented 13 meetings. The two counts use different bases.

Our reading · Proposals → Decide

A dissent that is written down is not the same as a dissent that is answered. When the evidence is disputed, the disagreement and the condition for deciding belong on the decision itself, where the people approving it have to respond to them.

Context and limits

This account follows the FDA’s own documents, a staff report by the majority staff of two House committees, and the HHS inspector general. It does not judge the drug’s science. Biogen said its 2024 decision to discontinue was not related to safety or efficacy concerns. People are described by role.

From the record to a design question

If the basis of the decision changes, which objections need to be examined again?

What this asks of the process

Retain reservations and the evidence behind them alongside each proposal. When the question or approval route changes, make clear what has been reconsidered, what remains open and who makes the call.

What we do not conclude

This is a process lesson, not a judgment on treatment. Software does not replace regulatory review, scientific expertise or the applicable approval standard.

This is our design inference from the case. The case does not test Sikizana. See the research that informs the sequence

Sources

  1. FDA, memorandum to the advisory committee chair on the approval (7 June 2021)
  2. FDA, approval letter, BLA 761178 (7 June 2021)
  3. FDA, statistical review, BLA 761178
  4. FDA, summary review, BLA 761178
  5. Majority staff, House Committees on Oversight and Reform and on Energy and Commerce, The High Price of Aduhelm’s Approval (29 December 2022)
  6. HHS Office of Inspector General, OEI-01-21-00400 (January 2025)
  7. Centers for Medicare & Medicaid Services, national coverage decision memo (7 April 2022)
  8. Biogen, announcement of 31 January 2024

Based on the linked official record, participants’ accounts and original research. Retrospective accounts and investigations have different limits; they are not controlled tests of a decision method. No organization named here is presented as a customer, partner or endorser of The Third Field.