In February, when Biogen Inc. said it was adding to the phase III effort with aducanumab in Alzheimer's disease (AD), language by the firm's chief medical officer (CMO), Alfred Sandrock, might have raised a red flag, or at least a pink one. "We did see more variability on the primary endpoint than assumed when we did the original sample size estimation, so we decided to increase the sample size" by 510 patients in the two studies, he said during a Leerink Partners health care conference.