Roche (SIX:RO, ROG; OTCQX:RHHBY) subsidiary Genentech announced that a study of the amyloid beta-protein inhibitor crenezumab failed to show statistically significant clinical benefit in Alzheimer’s patients. The failure is typical. Historically, 99% of Alzheimer’s drug candidate studies fail to show improvement over placebo, according to Alzheimer’s Research & Therapy. In the research, Genentech partnered with the…