AbbVie Inc.’s Board of Directors has recommended that stockholders vote against a proposed merger with Shire Plc.  The company attributed the recommendation to the impact of the Treasury’s proposed inversion regulations.   A statement released yesterday stated “the breadth and scope of the changes, including the unexpected nature of the exercise of administrative authority to impact longstanding tax principles, and to target specifically a subset of companies that would be treated differently than either other inverted companies or foreign domiciled entities, introduced an unacceptable level of uncertainty to the transaction.”  Under the terms of the agreement with Shire, AbbVie may be subject to a break-up fee of approximately $1.635 billion.