London: US pharmaceutical company AbbVie said it was reconsidering its $55 billion (Dh202 billion) takeover of Shire in the wake of US government moves to curb deals designed to cut tax, wiping $13 billion off the London-listed firm’s stock price. Chicago-based AbbVie said late on Tuesday it was responding to the US proposals which aim to make it harder for American firms to shift their tax bases out of the US and into lower cost jurisdictions in Europe. AbbVie’s move for Shire, a leader in drugs to treat attention deficit hyperactivity disorder (ADHD) and rare diseases, was announced in July amid a spate of similar takeover deals within the US and European pharmaceutical sector.