Monday was an up-and-down day on Wall Street, with indexes ultimately closing mixed. Gains in some major benchmarks were small as fears about a recession in Europe held stocks back early, but U.S. investors have higher hopes for the domestic economy to escape the same fate. Even so, some companies had to deal with challenges that sent their share prices lower. NIO (NYSE:NIO), Akcea Therapeutics (NASDAQ:AKCA), and Overstock.com (NASDAQ:OSTK) were among the worst performers. Here's why they did so poorly.

Could NIO face a roadblock ahead?

Shares of NIO fell 11% as investors got ready to get their latest reading on how the Chinese electric vehicle specialist's business is doing. Most auto industry watchers agree that China has huge potential to become a key player in producing cars and trucks that run on electricity, given the massive pollution problems facing the emerging economic power. NIO has a clear head start in helping to provide those solutions for the Chinese market, but a combination of factors including lower subsidies and poor quarterly results has hurt the automaker. Investors might get some reassurance early Tuesday when the company releases its latest results, but in advance of that, NIO shareholders seemed more comfortable heading for the sidelines rather than staying the course.

Blue NIO electric sportscar with upward-opening doors.

Image source: NIO.

Akcea sees an executive exodus

Akcea Therapeutics saw its stock drop 20% after a group of top executives left the biopharmaceutical company. CEO Paula Soteropoulos, COO Jeff Goldberg, and President Sarah Boyce all departed the company, with Soteropoulos and Boyce also resigning from the board of directors. The former CEO and COO will both work as advisors for transitional purposes, but the board appointed Damien McDevitt as interim CEO while Akcea looks for a permanent replacement. The shake-up came without much warning and sent the stock to its worst levels in more than a year. Without a quick turnaround, investors could lose confidence in Akcea's ability to develop and commercialize rare-disease treatments successfully.

Overstock sees tough times ahead

Finally, shares of Overstock.com plunged 25%. The company made the decision to name interim CEO Jonathan Johnson to be its permanent chief executive. Board Chair Allison Abraham expressed confidence in Johnson's ability to work in both the blockchain and retail segments, which will be crucial in mapping Overstock's future. Yet the company also said that third-quarter financial results will be weaker than expected, citing higher tariff-related costs, rising insurance premiums for its directors and officers, and generally weaker consumer confidence and search traffic conversion. Overstock has been trying to figure out which part of its business to focus on for a while, and it doesn't seem any clearer exactly what the company's future looks like than it did before the latest announcement.