These longtime leading biotech stocks still have plenty of upside ahead.October typically isn't a time investors look forward to in the markets. It has historically been associated with equities moving in the wrong direction, and sometimes experiencing full-blown market crashes. The broader market has performed pretty well so far this year, but could that come to a halt in October? Maybe.No matter what happens, investing in companies that will get through bear markets and perform well over the long run is a ...