Bill Ackman said he will “probably stay away from pharmaceutical companies” after losses at Valeant Pharmaceuticals International Inc. cost his hedge fund $4 billion. “What I learned is that it can be very expensive," Ackman, the billionaire activist investor and chief executive officer of Pershing Square Capital Management, said in a Bloomberg TV interview on Tuesday. Ackman, one of Valeant’s biggest supporters throughout its heyday and defenders when things turned sour, sold out of his stake in March after losing billions of dollars on the bet. “In the case of Valeant, we worked closely with the management team on the...