Chicago-based AbbVie has said it is reconsidering its $55bn (€43.4bn) takeover of Shire weeks after the US government moved to curb deals designed to reduce tax, wiping $13bn off the London-listed firm’s stock price.

Shares in Shire hit a record high yesterday on expectations of a takeover as dealmaking sweeps the drugs sector, after Reuters reported the group had hired investment bank Citi as a defence adviser.

Drugs giant AstraZeneca was today celebrating its latest victory in the battle to protect its most valuable medicines from cheaper, unauthorised copies.