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Aducanumab takes Biogen stock for a wild ride

Aducanumab is a monoclonal antibody that selectively targets and decreases levels of the amyloid beta plaques that are a hallmark of Alzheimer’s disease. After some success in development, Biogen found that its phase three trials, EMERGE and ENGAGE, satisfied futility criteria. Development of aducanumab ceased on March 21st, 2019, yet the story did not end there.

On October 22nd, 2019, Biogen announced that after reanalysis of their phase 3 trials EMERGE was found to show significant positive results. The company also claimed that a subset of patients in ENGAGE supported the positive results of EMERGE. On August 7th, 2020, the FDA accepted Biogen’s Biologics License Application with priority review status, setting the final decision date as March 7th, 2021. At the end of September, the FDA announced that it would hold an advisory committee meeting on November 6th, 2020 concerning aducanumab. After a mock panel of medical professionals offered an unfavorable view of aducanumab on October 19th, investors grew worried and Biogen’s stock started to slide down to $247.01 a share, down approximately 8% from the price at the time of the October 19th mock panel.

Biogen’s fortunes appeared to change on November 4th when the FDA released briefing documents concerning its position on aducanumab ahead of the advisory committee’s meeting. The briefing document took a notably positive tone, claiming that the results of EMERGE were “highly persuasive”. The FDA also appeared to agree with Biogen in that certain patients in the ENGAGE study showed results supporting EMERGE. This generally supportive view from the FDA caused Biogen stock to surge almost 44% to $355.63 a share. Despite this positive outlook going into the advisory committee’s meeting, trading of Biogen shares was frozen on November 6th in anticipation of a make-or-break moment for the stock.

A cursory glance of the recent history of the BIIB ticker will reveal that the advisory committee did not share the FDA’s positive views. The committee voted 0-10, one undecided, that the EMERGE trial alone could not be considered proof of the efficacy of aducanumab, especially considering the largely conflicting data from ENGAGE. After a weekend for the market to digest the committee’s scathing opinion, the price of Biogen stock was down over 28% to $236.26 a share. The stock recovered slightly in the ensuing week to $248.59 a share at the time of this post.

No matter the future of aducanumab, Biogen investors have likely experienced the most profound mood swing the stock market can provide. As of now, Biogen still plans to work with the FDA as the decision date of March 7th, 2021 marches closer. Despite the pessimism of many analysts, Biogen has still applied for a trademark on the proposed brand name Aduhelm.

Written by Christopher Biser, PharmD Candidate 2024, University of Pittsburgh School of Pharmacy



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