A Swiss private biotech company «AC Immune» has launched the world's first test of a vaccine against a protein believed to cause Alzheimer's disease, Newsmax Health reports.

Its ACI-35 vaccine aims to stimulate the immune system to produce antibodies which target the tau protein that forms twisted fibers and tangles inside the brain.

Many scientists believe tau is an important cause of Alzheimer's, alongside another protein known as amyloid, that has been the main focus of drug development efforts so far.

Although there is still no treatment that can effectively modify the disease or slow its progression, a number of big pharma companies - including Roche, Eli Lilly, Merck & Co and Johnson & Johnson - are pursuing a variety of approaches to get to the root cause.

AC Immune's Alzheimer's drug is the anti-Abeta antibody crenezumab which it licensed to Roche's subsidiary in 2006. Results of a Phase II trial of crenezumab are expected in the first half of this year and will be crucial for the company's next steps.

Over the past 15 years more than 100 experimental Alzheimer's drugs have failed in tests. Industry analysts believe that the prize for a truly effective drug could be a market worth $10 billion in annual sales.