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FDA praise for Biogen’s Alzheimer’s drug sends it stock soaring by nearly 44 percent

If approved, it would be the first new medicine to treat the disease in nearly two decades.

Biogen headquarters in Cambridge.John Tlumacki/Globe Staff/file

Biogen’s closely watched experimental drug for Alzheimer’s disease got a big boost Wednesday after reviewers for the Food and Drug Administration said it appeared to be safe and effective.

That conclusion, posted on the agency’s website in the morning, delighted investors. Biogen’s share price closed Wednesday at $355.63, up nearly 44 percent, two days before an FDA advisory committee plans to consider whether to recommend approval of aducanumab. The company ended the day with a market cap of $54.7 billion, up more than $16 billion.

The effect of the drug on patients in Biogen’s late-stage clinical trial was “robust and exceptionally persuasive on several of the instruments used to evaluate efficacy,” FDA reviewers concluded in a 343-page background document.


Kevin Krudys, a clinical analyst in the FDA’s neurology division, said in another document that Biogen has “provided substantial evidence of effectiveness to support approval."

If aducanumab is approved, it would be the first new Alzheimer’s medicine in nearly two decades and could become a blockbuster, meaning sales of at least $1 billion a year. An estimated 5.8 million Americans age 65 and older are living with Alzheimer’s, making it the sixth leading cause of death in the country, according to the Alzheimer’s Association.

Alethia Young, an analyst for Cantor Fitzgerald, wrote investors that the FDA material is “very supportive” of Biogen’s arguments that aducanumab, which has had a topsy-turvy history, should win approval.

“Simply put, if you look at the documents and see how many times in the FDA position box that they say ‘we agree,’ it suggests that Biogen’s key arguments are now well positioned” going into Friday’s advisory committee meeting, she wrote. The meeting is expected to culminate in a nonbinding vote.

Aducanumab is a monoclonal antibody designed to remove amyloid plaques from the brain. For years drug makers have targeted plaque buildup, but the efforts invariably failed and some researchers have called for a new approach. Biogen, collaborating with the Japanese drug firm Eisai Co., is one of the last big pharmaceutical companies pursuing treatments for Alzheimer’s because there have been so many setbacks.


Indeed if the FDA ends up approving aducanumab, it would represent a remarkable reversal of fortunes for Biogen, which has the largest workforce of any drug firm based in Massachusetts, with some 2,400 employees.

In March of last year, the company abruptly ended a pivotal trial of aducanumab after an early look at results indicated the drug did not provide a significant benefit. The news sent Biogen stock into a freefall, with the firm losing a staggering $18 billion of its value in a single day.

Seven months later, the biotech stunned many by reversing itself and saying it had decided to seek FDA approval after all. Biogen executives said their initial conclusion was wrong and that a look at a larger set of data showed that patients treated with the drug showed improvements in memory, orientation and language.

Although the FDA has approved other drugs to ease the symptoms of Alzheimer’s disease, such as Aricept and Namenda, those medicines do not alter the relentless course of the illness. Those drugs are taken orally.

In contrast, Biogen said in a document on the FDA website, aducanumab “has the potential to slow clinical decline, extending the time people can live with conserved cognitive abilities, preserving autonomy in activities of daily living, and lessening behavioral symptoms.” It would be administered intravenously for about an hour every four weeks.


Biogen specializes in medicines to treat neurological conditions such as multiple sclerosis and spinal muscular atrophy, a rare and deadly genetic disease. Sales of its multiple sclerosis drug, Tecfidera, have been falling amid competition from rivals, and Biogen has been eager to find another money-maker.

Jonathan Saltzman can be reached at