Biogen ( BIIB ) and its Japanese pharma partner Eisai said Thursday that they were halting two Phase 3 clinical trials of aducanumab, a drug that was designed to slow the worsening of Alzheimer's by targeting brain-destroying protein fragments known as beta-amyloid, STAT reports. An independent interim analysis concluded that aducanumab was unlikely to benefit Alzheimer's patients compared to placebo when the trials completed, Biogen and Eisai said.