Dementia: Is new drug a major breakthrough?

A new drug appears to slow down the progression of Alzheimer's disease – but only in certain cases.

Some scientists have hailed the results of the trial as a major breakthrough in a field that has seen little advancement in decades, but others are far more sceptical.

What is it and how does it work?

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LMTX is taken twice a day in tablet form. In the trial, it was used to treat 891 patients with mild to moderate Alzheimer's for 18 months, with the results presented at a conference in Toronto, Canada.

It is the first time a major drug trial has targeted tau tangles – abnormal clumps of protein that disrupt brain function – instead of beta-amyloid, a different type of protein that forms plaques as it accumulates in the brain, the New Scientist reports.

"The success of the LMTX trial suggests that tau tangles might be the main cause of Alzheimer's symptoms," it says.

How successful is it?

Overall, the trial was a flop as there appeared to be no benefit to taking LMTX, says the BBC's health and science correspondent, James Gallagher.

"However, an analysis on just the 15 per cent of the patients who had not already been taking drugs to help manage their symptoms showed a benefit," he adds. "In this tiny subset of patients, tests showed thinking power was maintained and MRI scans found the death of brain cells was reduced."

Claude Wischik, the co-founder of TauRx Pharmaceuticals, which developed the drug, said the results were unprecedented. "On the whole, [it] slowed progression by about 80 per cent," he says.

Though further testing is needed, LMTX has helped people get back to their daily lives, he says: "A wife of a patient told me her husband suddenly got up and fixed the garden fence, which he'd needed to do for years."

What has the reaction been?

The discovery was hailed by many, with the US Alzheimer's Association describing it as "a significant event" in the history of dementia research.

"In a field that has been plagued by consistent failures of novel drug candidates in late-stage clinical trials and where there has been no practical therapeutic advance for over a decade, I am excited," said Dr Serge Gauthier, the director of the Alzheimer's Disease Research Unit at McGill University, Canada.

Others, however, have urged caution. Alzheimer's Research UK's Dr David Reynolds said he was concerned LMTX appeared not to work alongside other medications.

"The data suggests it is slowing down the disease, but the important caveat is these small numbers," he said.

"It is encouraging, but we need more data and will have to run a study with it as just a monotherapy [on its own]," he added. "It will still be years from reaching patients, even assuming it works."

Dr Rachelle Doody, the director of the Alzheimer's disease and Memory Disorders Center at Baylor College of Medicine in Texas, was even more pessimistic. "To present it to the public now as a promising approach seems unjustified," she told the New York Times.