New York

BILL Ackman "deeply and profoundly" apologised for his investment in Valeant Pharmaceuticals International Inc, a "huge mistake" that cost his firm US$4 billion.

In his annual letter to investors in his publicly traded fund Pershing Square Holdings Ltd, Mr Ackman in part blamed Valeant's overpaying for Salix Pharmaceuticals in 2015 for the drugmaker's downfall. But he also took blame for misjudging the company's management and its aggressive strategy.