Australian scientists say they have identified a toxin that plays a key role in the onset of Alzheimer's, raising hope that a drug targeting the toxin could be developed and slow the disease.

The scientists say quinolinic acid kills nerve cells in the brain, leading to dysfunction and death.

Alzheimer's researcher Dr. Karen Cullen, of the University of Sydney, says the toxin may not be the cause of the disease, but it plays a key role in its progression.

The degenerative brain disease affects millions worldwide. Experts estimate in the U.S. alone, 16 million will be affected by 2015.

Over 200,000 have the disease in Australia, with that number expected to rise to 730,000 by 2050.

Quinolinic acid is part of a biochemical pathway called the kynurenine pathway, also found in other brain disorders, like Huntington's disease and schizophrenia.

The scientists say there are several drugs in advanced stages of development for other conditions which target this pathway and may be used to complement other treatments for Alzheimer's, once they are tested.