Biotech investors like to dream big. And right now, there's no bigger dream than owning stock in the first company to develop a truly effective drug against Alzheimer's disease. A new drug for Alzheimer's -- one that can stop or even reverse the insidious mind-destroying course of the disease -- is the biggest unclaimed prize in biotech. Such a drug will generate billions of dollars in sales for the company that develops it. As for the investors in that company, well, need I say more? The numbers tell the story: Between 4 million and 5 million people in the U.S. are diagnosed with Alzheimer's, a figure that could triple by the middle of this century as baby boomers (and the rest of us) age and live longer. Many baby boomers are now spending a fortune caring for parents with Alzheimer's. Tomorrow, the boomers themselves will be facing the tragedy of the disease, and their kids will bear the costs -- which are enormous. The Alzheimer's Association estimates direct and indirect costs of the disease now amount to more than $148 billion. Aricept, the leading Alzheimer's drug today, generates about $1 billion in sales for its owners Esai and Pfizer ( PFE). But it's only minimally effective. At best, it slows the rate at which Alzheimer's destroys the ability to think, to remember, to take care of one's self. To watch Janet Alvarez's video take of this column, click here .