Scientists offered cautious optimism on Thursday that an experimental drug might hold the key to treating neurodegenerative diseases like Alzheimer's or Parkinson's. The team from the University of Leicester published their report in the US journal Science Translational Medicine.

An experimental new treatment for lab mice was able to prevent the death of brain cells in mice affected with prion disease, part of a family of disorders better known for "mad cow disease" or Creuzfeldt-Jakob disease in humans. This comparatively rare disorder - especially in the case of humans - was chosen, among other reasons, for its rapid effects that allow for simpler study.

"This finding, I suspect will be judged by history as a turning point in the search for medicines to control and prevent Alzheimer's disease," Professor Roger Morris from King's College London said of the findings in an interview with the BBC. No treatment had previously succeeded in preventing brain cell death in mice with such disease.

The mice were divided into three groups, one of them treated seven weeks after infection, another after nine when degeneration became apparent, and the control group untreated. While alive, the treated mice demonstrated fewer signs of memory loss than the control group, and once dissected, examination showed that rate of brain cell death was very low - and lower again among the mice treated earliest.

"We were extremely excited when we saw the treatment stop the disease in its tracks and protect brain cells, restoring some normal behaviors and preventing memory loss in the mice," toxicology professor Giovanna Mallucci told Britain's Press Association.

Note of catution

"We're still a long way from a usable drug for humans," Malluci also said. "This compound has serious side effects."

It is also possible that the drug's promising effects on mice will not translate to a human brain, with over 1,000 times more neurons than a mouse's.

The researchers cautioned in the paper that a theoretical drug for humans would not cure illnesses, but rather prevent an unfortunate side-effect of the body's natural defenses, meaning people would need to take the drug "for years or even decades in many cases."

The death of brain cells caused by diseases like Alzheimer's is the result of a natural defense mechanism called the unfolded protein response, or UPR. Having recognized the build-up of rogue, unfolded proteins in the brain - a first stage of many such neurodegenerative illnesses - the organ shuts down protein production to stop the problem from spreading. However, the UPR can only halt all production of proteins, including those necessary over time to keep neurons alive and synapses functioning.

The researchers found that the drug, made by British firm GlaxoSmithKline and labeled GSK2606414, was able to keep protein production functioning in the brain by inhibiting a key enzyme that facilitates this process. In humans, however, inhibiting the PERK enzyme can lead to side-effects including weight loss and diabetes.

The World Health Organization estimates that Alzheimer's, the most common form of dementia, afflicts more than 35 million people around the world. Amid increasing life expectancies and population figures, that number is expected to rise sharply in the coming decades.

msh/av (AFP)