Valeant shares tumble to 2-1/2 year lows

By Caroline Humer and Svea Herbst-Bayliss NEW YORK/BOSTON (Reuters) - Valeant Pharmaceuticals International Inc shares fell as much as 20 percent on Thursday to a level not seen since 2013, heaping new pressure on Chief Executive Officer Michael Pearson after weeks of steep losses due to concerns about the drugmaker’s business practices. One new trigger for selling, said BMO analyst Alex Arfaei, may be a Wall Street Journal article on Thursday in which major Valeant investor Bill Ackman, w