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Biogen shares drop after Alzheimer’s drug trial setback

Michel Vounatsos is chief executive of Cambridge-based Biogen Inc.
Michel Vounatsos is chief executive of Cambridge-based Biogen Inc.(Dina Rudick/Globe Staff)

Shares of Biogen Inc. dropped more than 3 percent Thursday after the Cambridge biotech reported that an experimental Alzheimer’s drug it’s co-developing with a Japanese company showed disappointing results in a mid-stage clinical trial.

But the setback involves only one of a half dozen compounds Biogen is developing to target Alzheimer’s disease, the memory-ravaging neurodegenerative disorder that is expected to affect about one in nine baby boomers and cost the nation $1 trillion by 2050.

The findings have no bearing on Biogen’s lead Alzheimer’s drug candidate, called aducanumab, which uses a different mechanism to fight the disease. Over the past two years, Biogen has published encouraging data showing that aducanumab reduced the amyloid plaque buildup around neurons that many scientists have pegged as an Alzheimer’s trigger. That has slowed cognition decline in a small number of patients in early-stage studies.

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“Our research on Alzheimer’s continues,” Biogen spokesman Matt Fearer said Thursday. “Aducanumab is chugging along. This is an unrelated compound.”

Nonetheless, Biogen shares fell $10.95 to $322.52, a loss of 3.3 percent, after the drug being tested failed to meet a clinical measure set by Biogen and its partner, Tokyo-based Eisai Company Ltd., in a 12-month analysis. The clinical study involving 856 patients at 118 trial sites globally, will continue and the drug makers plan to conduct an updated analysts after 18 months.

Dozens of other experimental Alzheimer’s drug programs have failed over the past two decades, including well-capitalized efforts by pharmaceutical giants such as Merck & Co. and Eli Lilly & Co. More than a dozen new drug candidates are in late-stage trials, and Biogen is about halfway through enrolling the 2,700 patients worldwide for its late-stage trial of aducanumab.

But scientists remain a long way from developing a cure for Alzheimer’s.

Biogen, considered a front-runner in the race to develop the first treatment, is exploring other approaches beyond amyloid plaque, including one targeting neurofibrillary tangles made up of tau protein deposits in the brain. Its researchers are also seeking to understand the connection between amyloid and tau in the development of the neurodegenerative disorder.

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Robert Weisman can be reached at robert.weisman@globe.com. Follow him on Twitter @GlobeRobW.