Scottish researchers have discovered that a drug that's in its early stages of testing is effective at dissolving the protein tangles that form in the brains of Alzheimer's patients.

Methylthioninium chloride or MTC (Rember), when used at a 60-mg dose over 50 weeks, reduced cognitive decline by 81 per cent.

"These are the first very positive results I've seen" for stopping mental decline, said Marcelle Morrison-Bogorad, director of Alzheimer's research at the National Institute on Aging. "It's just fantastic."

The drug was developed by TauRx Therapeutics in Singapore.

The study's findings were presented Tuesday at the Alzheimer's Association International Conference on Alzheimer's Disease in Chicago.

MTC dissolves the tangles, which are made of a protein called tau, which builds up in the neurofibres of the brain and leads to dementia. MTC has also demonstrated that it can block the toxic effects of tau in cells.

Researchers at the University of Aberdeen in Scotland conducted a 24-week double-blind randomized trial of MTC in 321 patients in the United Kingdom and in Singapore. This initial study was followed by a 60-week blinded study extension.

They wanted to see the effectiveness of MTC at 30-, 60- and 100-mg doses three times a day in patients with mild to moderate Alzheimer's, and compare them to patients taking placebo.

Images show progress

Images of the patients' brains were taken at the beginning and after 24 weeks of treatment using positron emission tomography scans and single photon emission computed tomography scans.

Over 50 weeks, MTC stabilized the progression of Alzheimer's in patients with both mild and moderate forms of the disease.

The effect was most pronounced in people who had areas of the brain severely affected by tau, such as the hippocampus, which governs short-term memory and movement, and the entorhinal cortex, which governs memory and sense of direction.

Those patients taking both the 30- and 100-mg doses had less of a response than those taking 60 mg, researchers found.

"The people on placebo lost an average of seven per cent of their brain function over six months, whereas those on treatment didn't decline at all," said Claude Wischik, professor in Mental Health, at the University of Aberdeen.

"This trial therefore provides the first clinical trial evidence that an Alzheimer's therapy aimed at blocking tau aggregation may be a viable disease-modifying treatment. We now need to confirm this in a larger Phase 3 trial."

According to the Alzheimer's Society of Canada, an estimated 97,000 Canadians will develop Alzheimer's or a related disease this year. The society says an estimated 300,000 Canadians over 65 have the disease.

With files from the Associated Press