BUZZ-Valeant Pharmaceuticals International Inc: Ackman sells shares
** Embattled Canadian drugmaker's U.S.-listed shares down 4 pct at $97.51 premarket
** Billionaire investor William Ackman said on Thursday he sold about 5 mln Valeant shares in order to generate tax loss as investors in his Pershing Square Capital Management face biggest loss in company's history
** News comes at tail end of tumultuous year for Valeant , whose share price had surged and then plummeted amid questions about its drug pricing and accounting practices
** Valeant, after disclosing in late December that CEO Michael Pearson had been hospitalized with severe pneumonia, named trio of company executives to take over until Pearson returns
** Up to Thursday's close, stock had fallen about 11 pct since Dec. 24, the last trading day before company announced its interim management team
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