Biogen Stock Tumbles on Brutal Takedown of Its Alzheimer's Drug Bet

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Happy Monday, readers. I hope you had a wonderful Thanksgiving weekend.

Biogen stock fell nearly 2.5% in Monday trading, shedding nearly $2 billion off the biotech giant’s market value. The apparent culprit? A scathing investor note from Baird analyst Brian Skorney that poured cold water on the prospect of aducanumab, the experimental Alzheimer’s drug that Biogen unexpectedly brought back from the grave, winning Food and Drug Administration (FDA) approval.

For some background: Biogen stunned the biotech community in late October when it announced it would be reviving aducanumab and submit it to the FDA for regulatory green light. This highly unusual (and potentially unprecedented) move came some seven months after the company had abandoned late-stage trials of the drug following a “futility analysis.”

Biogen justified the turnaround by saying that a new, more nuanced analysis of the dataset showed it could, in fact, slow the rate of cognitive decline in certain Alzheimer’s patients. When I spoke with Biogen CEO Michel Vounatsos immediately following the reversal, he struck a confident note. “The decision was part of a new analysis of the dataset. The ‘T’s were crossed and the ‘I’s were dotted,” he told me.

Skorney very much begs to differ.

“The fact is, the prospectively defined pivotal program failed, making any further analyses exploratory in nature and any p values reported nominal. To make claims otherwise is statistical malpractice,” he wrote. (P-values are a statistical metric used to assess the probability of success that an observed claim is valid.) “The bottom line is, the FDA standard of approval is substantial evidence of efficacy and the cumulative data for aducanumab falls really far short of this standard.”

That bear thesis appears to have at least some investors shook. Still, given the lack of treatment options in the space, it’s not impossible to imagine the FDA could defy the critics and get aducanumab to market.

Biogen declined to comment on Skorney’s criticism in an emailed statement.

Read on for the day’s news.

Sy Mukherjee
sayak.mukherjee@fortune.com
@the_sy_guy

DIGITAL HEALTH

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INDICATIONS

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THE BIG PICTURE

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