(Bloomberg) -- Just days after Biogen Inc. revealed promising early data from an experimental Alzheimer’s treatment, new research from the Mayo Clinic may revive a long-running debate over whether the drug industry is focusing on the right target in developing therapies to treat the disease.
Related Stories
Biogen Soars as Alzheimer's Drug Slows Disease in Trial Bloomberg
Biogen’s Alzheimer’s Drug Impresses in Early Trial The Wall Street Journal
Moment of truth for Biogen's big Alzheimer's bet CNBC
Biogen shares soar on optimistic Alzheimer's drug study data Associated Press
How Biogen scored the most successful Alzheimer’s drug so far Fortune
The study, published Tuesday in the journal Brain, found that the accumulation of dysfunctional tau protein is the real source of cognitive decline and memory loss seen in Alzheimer’s. Tau destabilizes tracks used by cells to transport food and messages throughout the brain, the research found.
More from Bloomberg.com: Freeport-McMoRan Cuts Dividend 84% After Commodities Drop
Biogen’s drug BIIB037, and several others in advanced development, focus instead on the buildup of different set of protein fragments, called beta amyloid.
“Amyloid has a relationship with cognitive decline, but if you’re looking at both of them together, tau is the bad guy,” Melissa Murray, a neuroscientist at the Mayo Clinic campus in Jacksonville, Florida, said in a telephone interview. The majority of research into the disease has focused on beta amyloid over the past 25 years, she said.
The researchers examined more than 3,600 brains from patients who died at different stages of dementia, with Alzheimer’s confirmed in almost 1,400. Measuring amyloid and tau in the brains at various stages of disease progression allowed them to conclude that it was the level of tau that predicted how quickly a person’s mental faculties had deteriorated.
More from Bloomberg.com: Netanyahu Apologizes to Israeli Arabs
Cognitive decline typically begins when abnormal tau accumulates in the memory center of the brain –- the hippocampus. Ultimately, toxic tau accumulates in the cortex, the part of the brain involved in higher levels of thinking, planning, behavior and attention, Murray said.
Drug Development
Companies including Johnson & Johnson, Biogen and AbbVie Inc. have products in the early stages of development that target tau in the brain. TauRx Pharmaceuticals Ltd., a closely held, Singapore-based drug developer, is testing a tau-targeting compound in broader human trials.
More from Bloomberg.com: U.S. Cost of Living Rose More Than Forecast
The Mayo Clinic study doesn’t discount the idea that beta amyloid may be involved in Alzheimer’s progression. The findings may indicate that scientists need to consider multiple approaches and targets, said Dean Hartley, director of science initiatives at the Alzheimer’s Association.
“Depending on where you are in the disease, you may need certain types of treatments,” Hartley said. “If you’re later in the disease, maybe tau is extremely important, but if we don’t want any of the clinical symptoms to develop, then maybe we want to target amyloid.”
Promising Data
On Friday, Biogen released early-stage clinical trial data showing that its experimental Alzheimer’s drug clearly reversed the build-up of beta amyloid in the brain and also showed signs of reducing cognitive decline. The company’s shares shot up 10 percent on the news. Analysts said the therapy, if successful in later-stage trials and approved, could become a more than $10 billion drug for Biogen and partner Eisai Co.
That’s just one amyloid-targeting therapy in trials. Eli Lilly & Co. is currently retesting its drug solanezumab in earlier-stage patients. Roche Holding AG is continuing to sponsor a trial of its amyloid-targeting drug in Alzheimer’s patients with mild dementia, though in December it abandoned a study of people with early stages of the disease because of poor results.
To contact the reporter on this story: Cynthia Koons in New York at ckoons@bloomberg.net
To contact the editors responsible for this story: Crayton Harrison at tharrison5@bloomberg.net Drew Armstrong
News 
Market Data 
Discover 
