Billionaire hedge fund manager William Ackman’s Pershing Square Holdings portfolio has lost 24.5 percent this year, extending its fall this week as its biggest holding, Valeant Pharmaceuticals, declined further, the company said on its website. Valeant’s stock price (VRX.TO) has tumbled 72 percent from its high this summer with the losses accelerating in recent weeks amid questions about the company’s accounting and business practices and criticisms for price gouging. Ackman’s $14.5 billion Pershing Square Capital Management paid roughly $186 per share for its 21.4 million shares of Valeant.