LONDON – The American drug maker AbbVie said on Tuesday it had raised its bid to acquire Shire, the Irish drug maker that has already rejected its previous takeover offer worth $46 billion.
AbbVie, based in Chicago, said it was now offering cash and stock worth 51.15 pounds a share, or about $87.66. That is up 11 percent from its previous offer of cash and stock. The revised offer is worth about $51.6 billion.
The drug maker, which was spun off from Abbott Laboratories, is the latest American company to attempt what is called an inversion, in which it would acquire an overseas company and reincorporate to avoid higher corporate taxes in the United States and free up cash held overseas.
The board of directors of Shire, which is based in Ireland and listed in London, has said AbbVie’s earlier takeover approaches — Tuesday’s bid was the fourth since May — significantly undervalued the company and its prospects.
Shire, which has its US headquarters in Lexington, Mass., has also expressed concern about the potential execution risk of such a deal, particularly the tax structure.
“AbbVie has made a compelling offer to Shire that creates immediate and long-term value to shareholders of both companies,” Richard A. Gonzalez, chief executive of Abb-Vie, said in a statement.
In formulating its latest proposal, AbbVie said it and its adviser, JPMorgan Chase, had spoken with shareholders who account for a majority of Shire’s outstanding shares.
Under British rules, AbbVie has until July 18 to make a firm offer for Shire or walk away for up to six months.
Shire has argued that it should remain independent, saying it could more than double its revenue in the next seven years, to about $10 billion.