The Horizon Therapeutics sweepstakes has come to a close as Amgen announced Monday morning that it is acquiring Irish rare-disease biotech for $28.5 billion.

The board of directors of both companies reached an agreement on the cash offer of $116.50 per Horizon share. This includes a nearly 48% premium to the company’s closing share price on November 29. This was the last day before Horizon announced a possible offer under Rule 2.4 of the Irish Takeover Rules.

Additionally, the offer includes a nearly 20% premium to the company’s closing share price on December 9.

The deal is subject to shareholder approval, sanction by the Irish High Court and required antitrust clearances in the U.S., Austria and Germany. Amgen said it expects to receive regulatory approval during the first half of 2023. 

This is not only one of the biggest pharma M&A deals of the year but also the latest transaction for Amgen. 

In mid-October, the company closed a $3.7 billion deal to buy ChemoCentryx, a company focused on developing orally administered treatments for autoimmune diseases, inflammatory disorders and cancer. 

For his part, Amgen CEO Robert A. Bradway said the Horizon acquisition would drive Amgen’s revenue and is expected to be accretive from 2024. 

“The acquisition of Horizon is a compelling opportunity for Amgen and one that is consistent with our strategy of delivering long-term growth by providing innovative medicines that address the needs of patients who suffer from serious diseases,” Bradway said in a statement. 

According to its latest earnings report, Amgen said that it had a free cash flow of $2.8 billion at the end of Q3.

Earlier this month, Amgen was one of three pharma companies, including Sanofi and Janssen, to express interest in taking over Horizon. Following highly preliminary discussions, Janssen ultimately pulled out of the running last week but Sanofi announced the same day as Amgen that any potential bid for Horizon would solely be in cash. 

In accordance with the Irish Takeover Rules, any offeror was required to submit a bid no later than 5 p.m. Eastern Standard Time on January 10, 2023. 

Horizon CEO Tim Walbert said that Amgen is aligned with the company’s commitment and passion around driving innovation and delivering results in the autoimmune and severe inflammatory diseases space.

“In nearly 15 years, we have built one of the fastest growing and most respected companies in the biotechnology industry from the ground up,” Walbert said in a statement. “We have accomplished a tremendous amount for patients, their families and our customers, and created significant value for shareholders. These accomplishments are all rooted in our employees’ deep commitment, dedication and personal passion for those impacted by rare, autoimmune and severe inflammatory diseases.”