When a biotech company develops a drug candidate that can help millions of people fight a monstrous disease such as Alzheimer's, it will certainly gain attention from scientists, the news media, and the U.S. Food and Drug Administration. For Prothena (NASDAQ: PRTA), a huge wave of attention has also come from investors since the start of the year. Or is this just a sign of more gains to come as it develops a potentially best-in-class Alzheimer's disease portfolio to enter a market projected to grow by 5.4% per year through 2026, to reach $9 billion?