However, AstraZeneca's advisers would have received an extra payout if Pfizer's bid had gone hostile.

Air Products and Chemicals Inc APD.N has gone hostile in its bid for rival Airgas Inc ARG.N.

A deal with Alleghany could help Transatlantic ward off rival Validus Holdings Ltd, which has gone hostile in its attempt to buy the company.

Omnicare had gone hostile with its $15-per-share bid in September 2011, after PharMerica's board had rejected its approach.