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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

Dexcom's diabetes debacle. Parents of children with diabetes who used some of Dexcom's continuous glucose monitoring devices woke up to a major shock on Saturday of the holiday weekend—certain applications meant to ping caregivers about concerning oscillations in patients' blood sugar levels had gone dark late Friday evening. And parents weren't alerted to that outage until Saturday morning, hours after the breakdown occurred—which could have proven deadly seeing as it's entirely possible for children with type 1 diabetes to experience sharp falls or spikes in blood glucose while asleep. For more on this debacle, you can read my writeup of the company's explanations thus far, and the furious reactions of parents who rely on Dexcom's technology. (Fortune)

INDICATIONS

Neurocrine, Xenon strike epilepsy drug partnership. Neurocrine Biosciences and Xenon Pharmaceuticals have reached a licensing and collaboration deal for a new class of experimental epilepsy drugs. The treatment at the heart of the partnership, XEN901, seeks to treat a rare form of epilepsy in the $30 million cash deal (with potential downstream payments that could add up to $1.7 billion). And, if successful, it would expand Neurocrine's portfolio beyond its pioneering FDA green light for tardive dyskinesia therapy Ingrezza, which treats a serious side effect of some people using antipsychotic medications.

Sanofi to sell surgical product unit for $350 million. Sanofi has reached a deal to sell its surgical products unit Seprafilm to Baxter International for a cool $350 million in cash. It's the latest strategic shift by Sanofi CEO Paul Hudson, who's only been on the top job since September and is conducting a top-to-bottom review of the French pharma giant's portfolio. (Reuters)

THE BIG PICTURE

The real "sixth sense." Vox's Brian Resnick has an absolutely fascinating piece up on the phenomenon of "proprioception" (no, it's not a sequel to the hit Christopher Nolan movie about dream thieves—it might actually be cooler). This is the ability to recognize the location of our limbs when our eyes are closed. And, remarkably enough, there are certain people who actually don't have this nearly-universal sense, which can make it extremely difficult for them to, say, locate their noses in the dark or with their eyes closed. (Vox)