Illinois-based AbbVie has convinced the specialty pharmaceutical firm Shire to merge with it. AbbVie will pay about $54 billion in cash and stock to the Irish firm’s shareholders, who will own 25% of the combined company. The offer represents a 53% premium to Shire’s stock price in early May, when AbbVie first proposed a merger. It’s also 35% higher than AbbVie’s original offer. AbbVie was looking to diversify because more than half of its $19 billion in 2013 revenues came from the anti-inflammatory drug Humira, which loses patent protection in 2016. Major areas for the new firm will include immunology, rare diseases, neuroscience, metabolic diseases, hepatitis C, and oncology. The merger will also allow AbbVie to set up U.K. headquarters and lower its tax rate to about 13% from 22%. Lawmakers have responded negatively to such tax inversion moves by AbbVie and other U.S. companies. In May, legislators introduced bills in Congress after Pfizer attempted and failed to acquire London-based AstraZeneca. And U.S. Treasury Department Secretary Jacob J. Lew has asked House and Senate leaders to ban inversions retroactive to May. But policy analysts do not anticipate any legislative changes happening this year.