Switzerland-based Roche launched an unsolicited offer of $3bn (€2.2bn) for a US medical systems company, as hostile deals nearly quadruple compared to 2006.

Roche said it launched an offer for Ventana Medical, a maker of cancer diagnostic systems, for $75 a share. The price is a 44% premium to Ventana's last close and a 55% premium to its three-month average stock price.