Dublin-based drugs maker Shire said Monday it had entered "detailed discussions" with AbbVie about a $54 billion takeover proposal. It is AbbVie's fifth takeover proposal for Shire. If the deal is successful, the combined entity would become the ninth-largest drugs company in the world. Meanwhile, other U.S. companies looking to reduce their tax bills by switching their domicile have recently failed to acquire London-listed healthcare targets. Pfizer for instance, pulled a roughly $120 billion bid for AstraZeneca in late May after the latter rejected a string of proposals. The Deal's Sarah Pringle spoke with The Deal's European Editor Laura Board about the deal.