Roche on Wednesday night opened the door to raising its $3bn offer for Ventana if the US diagnostics company gave it access to internal information.

In a letter to Jack Schuler, Ventana’s chairman, Franz Humer, Roche’s chairman and chief executive, noted: “To the extent that you believe that Ventana has additional information that would support a valuation in excess of our offer, we would be willing to consider it in a negotiation with you.”