Roche ups Alzheimer's bet with new AC Immune deal LONDON (Reuters) - Switzerland-based Roche has bought the rights to a second type of experimental Alzheimer's drug from privately-held AC Immune, raising its bet on finding a treatment for the degenerative brain disorder. Roche's Genentech unit will make an undisclosed upfront payment and pay up to 400 million Swiss francs ($420 million) in milestones, based on the success of the anti-Tau antibodies in clinical development, AC Immune of Lausanne said on Monday. The deal tightens the relationship between the two firms as Roche has already acquired rights to another drug, crenezumab, that is designed to bind to beta amyloid, which causes plaques in the brain linked to Alzheimer's. Some scientists think that Tau protein may be a second major cause of Alzheimer's besides amyloid, since it forms twisted fiber and tangles inside brain cells. Roche is best known as the world's biggest maker of cancer drugs but the Basel-based company also hopes it can apply its understanding of disease complexity to the equally difficult world of Alzheimer's. The first deal with AC Immune for crenezumab, signed in 2006, won a notable vote of confidence last month when the U.S. government decided to back a clinical trial testing the drug among members of an extended family in Colombia who carry a gene that causes early Alzheimer's. $1 = 0.9513 Swiss francs Reporting by Ben Hirschler; Editing by Mark Potter