Johnson & Johnson (JNJ) and Pfizer Inc.’s experimental Alzheimer’s medicine may reduce the development of tau tangles in the brain, a hallmark trait of the degenerative condition, a small study suggested.

More than 5 million Americans have Alzheimer’s, a disease marked by the buildup of amyloid plaque and snarls of the tau protein. The drug bapineuzumab is being jointly developed by J&J and Pfizer to attack the disorder.

The study, reported in the Archives of Neurology, is the first to suggest it may work on the tau side of the disease. While the data showed no difference in beta amyloid levels, the drug reduced levels of a two forms of tau, according to the researchers from the University of Gothenburg in Sweden.

It’s not clear whether the changes will translate into a clinical benefit, the scientists said. The study analyzed cerebral spinal fluid for 27 patients treated with bapineuzumab and 19 given a placebo.

Results from the first pivotal trial designed to show if bapineuzumab can slow the progression of Alzheimer’s disease, rather than just ease its symptoms, is expected later this year. At least a dozen potential treatments for Alzheimer’s disease in mid- to late-stage testing have failed in the last decade.

J&J, based in New Brunswick, New Jersey, gained its share in the drug with its 2009 purchase (ELN) of an 18 percent stake in Dublin-based Elan Corp. for $1 billion. Elan and Wyeth, which New York-based Pfizer (PFE) acquired in 2009, funded the study.

To contact the reporter on this story: Michelle Fay Cortez in Minneapolis at mcortez@bloomberg.net

To contact the editor responsible for this story: Reg Gale at rgale5@bloomberg.net.