AP Biotechnology Writer SAN FRANCISCO — It's tragedy enough that Pat Williams' mother has Alzheimer's disease. But Williams is also terrified because her chances of inheriting the disease are much better than average. So Williams eagerly enrolled her 90-year-old mother last year in a massive, 1,600-patient, 18-month clinical trial testing an experimental drug made by the biotechnology company Myriad Genetics Inc. The drug, called Flurizan, slowed the mind-robbing disease in some of the 128 patients with mild Alzheimer's participating in a smaller test. Based on those results, the company has gambled millions of research dollars on the largest-ever Alzheimer's drug...