Perpetual takeover target Shire (NASDAQ: SHPG) is officially in play.

Long rumored as a takeover candidate given its strong ADHD franchise, its orphan drug focus, and most importantly its low Irish tax rates, Shire has an actual suitor in big pharma AbbVie (ABBV 0.98%). However, its private solicitations weren't enough to get a deal done, so the big pharma is making its case publicly for the newest tax-fleeing, inversion deal.

Shots have been fired and Shire is fighting back. Not wanting to be an easy acquisition or even the subject of a bidding war company management made its case as a stand alone entity highlighting sustainable double digit growth that is undervalued by AbbVie's $46.5 billion offer.

In this episode of Market Check-Up, the Motley Fool's health care focused investing show, analysts David Williamson and Michael Douglass, discuss the AbbVie's offer, what makes Shire so attractive, and why a bidding war could likely emerge. Watch and find out.