The drug company decided not to pursue further studies because its patent on the drug is about to expire:

A team of researchers inside Pfizer made a startling find in 2015: The company’s blockbuster rheumatoid arthritis therapy Enbrel, a powerful anti-inflammatory drug, appeared to reduce the risk of Alzheimer’s disease by 64 percent.

The results were from an analysis of hundreds of thousands of insurance claims. Verifying that the drug would actually have that effect in people would require a costly clinical trial — and after several years of internal discussion, Pfizer opted against further investigation and chose not to make the data public, the company confirmed.

Researchers in the company’s division of inflammation and immunology urged Pfizer to conduct a clinical trial on thousands of patients, which they estimated would cost $80 million, to see if the signal contained in the data was real, according to an internal company document obtained by The Washington Post.

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The company told The Post that it decided during its three years of internal reviews that Enbrel did not show promise for Alzheimer’s prevention because the drug does not directly reach brain tissue. It deemed the likelihood of a successful clinical trial to be low. A synopsis of its statistical findings prepared for outside publication, it says, did not meet its “rigorous scientific standards.’’

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Some outside scientists disagree with Pfizer’s assessment that studying Enbrel’s potential in Alzheimer’s prevention is a scientific dead end. Rather, they say, it could hold important clues to combating the disease and slowing cognitive decline in its earliest stages.

Some outside scientists disagree with Pfizer’s assessment that studying Enbrel’s potential in Alzheimer’s prevention is a scientific dead end. Rather, they say, it could hold important clues to combating the disease and slowing cognitive decline in its earliest stages.

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Meanwhile, Enbrel has reached the end of its patent life. Profits are dwindling as generic competition emerges, diminishing financial incentives for further research into Enbrel and other drugs in its class.

Capitalism, you gotta love it.