When Biogen and its partner Eisai announced in March that they’d halted two simultaneous Phase 3 clinical trials on an Alzheimer’s drug based on disappointing preliminary data, the development was seen as the latest in a string of high-profile failures of once-promising experimental drugs for the disease. For some observers, the failures cast doubt on the longstanding idea that the culprit in Alzheimer’s is amyloid plaques in the brain, given that Biogen’s drug, aducanumab, and other candidates had targeted the plaques. 

Then, in October, Biogen and Eisai unexpectedly reversed themselves, announcing that after analyzing more data from the stopped trials, they’d seek approval for aducanumab after all. Yesterday (December 5), in San Diego, Biogen presented the data the company says led to that decision.

Trial participants were people in the early stages of Alzheimer’s disease. In one of the two trials, those who received the...

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Some of the participants had been started on lower doses of the drug due to safety concerns but later switched to the high-dose group. When the company limited its analysis only to the subsets of patients who’d consistently received the high dose, it saw more consistent results: those in one trial had had 30 percent less mental decline over a year and a half compared with the placebo, while those in the other trial had 27 percent less decline. Brain scans also showed that patients taking the drug had less amyloid in their brains, and less tau, another Alzheimer’s associated protein. Some of those who received the highest dose had signs of brain swelling or bleeding in scans, but few showed symptoms stemming from these issues, according to Biogen.

The results are “exhilarating, not just to the scientific community but our patients as well,” said Sharon Cohen, a behavioral neurologist at the Toronto Memory Program and a principal investigator in the trials who received funding from Biogen, according to Science News. She added, “those of us who know this disease well know what it means to lose yourself slice by slice. Anything you can hang onto, and do well, is a triumph.”

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Not all experts were so enthusiastic. “I surely don’t think that it should be given market approval on the basis of these data,” Robert Howard, a psychiatrist at University College London, tells Science. “[Biogen has] broken all the rules, really, about how you analyze data and report it.” Howard also published a skeptical take on the drug in Nature Reviews Neurology last week. 

Yet Zaven Khachaturian, editor-in-chief of the journal Alzheimer’s & Dementia, tells Science that conditional approval of aducanumab may be warranted. The drug “may have all kinds of blemishes,” he says, but, “I would say, give it a chance with the hope that others will come in and improve on this compound, this strategy. Because now we have a way of affecting the course of the disease.”

Shawna Williams is an associate editor at The Scientist. Email her at swilliams@the-scientist.com or follow her on Twitter @coloradan.

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an illustration showing amyloid plaques around brain cells

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