The first of a new class of treatments for Alzheimer's disease has been shown to be more than twice as effective as existing drugs in slowing progression of the condition, scientists said yesterday.

The drug, Rember, is the latest of a group of new treatments for the degenerative disease announced in the past two weeks but one with the greatest potential, experts said.

Rember is the first drug to act on the nerve tangles discovered by Alois Alzheimer a century ago which are thought to be the cause of the disease. The early (Phase 2) trial of 321 patients showed it slowed progression by 81 per cent compared with placebos.

The Alzheimer's Society described Rember as "a major new development" and said the results were "potentially exciting" but warned larger trials were needed. The drug was developed by scientists at the University of Aberdeen working with the Singapore-based company TauRx Therapeutics – a spin off from the university.

Professor Claude Wishcik, chairman of TauRx, who presented the findings at the International Conference on Alzheimer's Disease in Chicago yesterday, said: "This is an unprecedented result in the treatment of Alzheimer's Disease. We have demonstrated for the first time that it may be possible to arrest progression by targeting the tangles."

In a separate development, scientists from Imperial College London and the University of Uppsala, Sweden, reported that a new drug, PBT2, slows the build-up of protein leading to plaques. Results of the early trial, published in The Lancet Neurology and presented to the conference, show patients who took the drug over 12 weeks had significantly improved cognitive performance.