Ackman's Pershing Square off 12.6 pct for year after Valeant tumble

BOSTON, Oct 1 (Reuters) - Billionaire hedge fund manager William Ackman's Pershing Square Holdings fund is nursing a 12.6 percent loss for 2015, an investor who received Ackman's letter on Thursday said, marking a dramatic reversal of fortune for one of last year's best performing managers.