Vertex Pharmaceuticals (VRTX 0.16%) was on track to become one of this year's biotech winners, with the shares climbing 27% from January through a peak in November. The company, the global leader in cystic fibrosis (CF) treatments, has established a long track record of earnings growth thanks to this business -- and in recent times has made significant progress on broadening into other billion-dollar treatment areas.But in recent weeks, Vertex stock has declined, and last week it lost nearly 12% in one trad ...