Thomson Reuters
William Ackman, founder and CEO of hedge fund Pershing Square Capital Management
Pershing Square Holdings, which trades in Amsterdam, fell more than 10.17%, or $1.53, to last trade around $13.52.
Ackman is the largest hedge fund shareholder of Valeant Pharmaceuticals. The hedge fund owns more than 21.5 million shares of the Canadian pharmaceutical company.
Valeant's share price collapsed on Tuesday after the company reported fourth-quarter earnings results that fell below analysts expectations and cut its revenue forecast for the year by about $1.5 billion, or 12%.
Valeant's stock was last down $30.88, or down 44.73%, at $38.16 per share. It hit a 52-week low of $37.24.
Ackman's lost more than $666 million on paper on his Valeant position since Monday's close. His losses to date on his Valeant investment are estimated at north of $2 billion.
Pershing Square Holdings' performance was down 19.3% for the year through March 8. The fund's latest performance data is expected to come out this week.
It follows a brutal 2015, when the fund fell more than 20.5%, making it the worst year in its history.
Here's a one-day chart:
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