AbbVie fails once again to buy British drugmaker Shire. In its fourth attempt, AbbVie offered a bid for about $46.5 billion. In a statement Friday, Shire said the proposal was "highly conditional" and undervalued the company. Analysts think the news of this failed bid could bring on a bidding war for Shire from AbbVie's competitors. U.S. drugmakers are attracted to the company for its rare disease business and tax base in Ireland. Overseas deals are speeding up as U.S. companies search for lower taxes and havens. But "AbbVie will likely be back but may not be able to pay much more," said Ronny Gal, senior analyst with Sanford Bernstein in note to clients.