The head of Roche has expressed renewed confidence that he will win his $3bn hostile bid for Ventana, the US diagnostic company, after claiming hedge funds have already bought out the leading shareholders.

Franz Humer, chairman and chief executive of the Swiss pharmaceutical group, told the Financial Times that he had “no intention of increasing the price” of the $75-a-share bid for Ventana he announced in June, and remained “very confident” of the success of the offer, which closes on November 1.