Amgen Inc. and Novartis AG announced Thursday afternoon that they will discontinue a study into a potential Alzheimer's disease prevention therapy after patients in the study showed worsening conditions. "An assessment of unblinded data during a regular pre-planned review identified worsening in some measures of cognitive function," the companies said in a joint announcement. "The sponsors concluded that the potential benefit for participants in the studies did not outweigh the risk." The phase 2/3 study, performed in conjunction with Banner Alzheimer's Institute, was testing the BACE1 inhibitor CNP520, or umibecestat, which is an amyloid-focused drug. Biogen Inc. failed in testing of an amyloid-focused drug earlier this year, leading some to predict that focusing on the sticky protein found in the brain could be a losing route to a drug for the debilitating neurodegenerative disease. "We still believe amyloid plays an important but complex role in Alzheimer's disease," Amgen executive David Reese said in Thursday's announcement. Novartis shares were down 1.5% in after-hours trading Thursday, while Amgen shares were not moving after the announcement.