abbvieBrunswick Group handles AbbVie's $54B bid for Ireland's Shire, a deal widely reported in the media as a means to escape the US tax bite.

AbbVie, the former research-oriented biopharmaceutical unit of Abbott Laboratories, says the combination "would create a global market leader with unique characteristics and a compelling investment thesis."

Shire, working with FTI Consulting, has rebuffed recent takeover overtures from its suitor. CEO Flemming Ornskov last month said he sees little overlap in the therapeutic areas of both companies.

To him, "the main strategic rationale here is tax inversion."

AbbVie, which says Shire offers a route to diversification, expects the deal would lower the combined company's tax rate to 13 percent by 2016 from the current 22 percent.

The Wall Street Journal today reported about the frenzy of tax dodge deals, triggered by a fear that Washington may act to eliminate the inversion route.

A Congressional Research Service study found the inversions will cost the Treasury Dept. $20B in tax revenues during the next decade.