Staff Writer
Columbus CEO

c.2013 New York Times News Service

LONDON — The Irish pharmaceutical company Shire has agreed to pay $4.2 billion in cash to acquire ViroPharma, a Pennsylvania biopharmaceutical firm, in a move intended to bolster its roster of treatments for rare diseases, the companies said Monday.

Shire will acquire all of the outstanding shares of ViroPharma for $50 a share, 27 percent above ViroPharma’s closing price Friday.

“The acquisition of ViroPharma will immediately benefit Shire and is entirely consistent with our clear strategic objective of strengthening our rare disease portfolio,” said Flemming Ornskov, Shire’s chief executive. “It brings us a new growth driving product which augments our already strong growth prospects.”

ViroPharma’s products include Cinryze, a treatment for hereditary angioedema, a rare blood disorder. The firm had $428 million in net revenue last year, the bulk of it from Cinryze.

Shire manufactures Firazyr, an injection to treat attacks of acute hereditary angioedema. It is probably best known for its drugs to treat attention deficit hyperactivity disorder, Vyvanse and Adderall XR. Shire’s shares were up 2.9 percent, at 2,876 pence, or $46.05, in trading in London on Monday morning.

“By joining with Shire, ViroPharma will become part of a larger, more diverse biopharmaceutical company and will benefit from Shire’s innovation, scale and global reach,” said Vincent J. Milano, ViroPharma’s chairman and chief executive.

With the acquisition, Shire expects its rare disease business to post $2 billion in revenue in 2014 and to represent 40 percent of its revenue on a pro forma basis.

Pending antitrust approval by regulators, the deal is expected to close by the end of this year or in the first quarter of 2014.

Shire said it intended to terminate its share buyback program after the announcement.

Lazard and Morgan Stanley acted as financial advisers to Shire, while Goldman Sachs was ViroPharma’s financial adviser. Davis Polk & Wardwell was Shire’s legal adviser on the deal and Skadden, Arps, Slate, Meagher & Flom was ViroPharma’s legal adviser.