Amgen has agreed to acquire Irish biopharmaceutical company Horizon Therapeutics in an all-cash transaction valued at $27.8bn.

Under the terms of the deal, Amgen’s newly formed wholly-owned subsidiary Pillartree will buy the entire issued and outstanding shares of Horizon for $116.50 per share.

The transaction price represents around 47.9% premium to the closing price of $78.76 per Horizon share on 29 November 2022 and implies an enterprise value of around $28.3bn.

Horizon’s board of directors have unanimously recommended the transaction.

The acquisition will be implemented by way of an Irish High Court-sanctioned scheme of arrangement under the Irish Companies Act.

The Scheme is anticipated to be declared in the first half of 2023, subject to obtaining the necessary regulatory approvals

Horizon Therapeutics chairman, president, and chief executive officer Tim Walbert said: “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.

“Amgen is aligned with that commitment and passion and will continue to maximise the value of the current portfolio and pipeline and accelerate the ability to reach more patients globally.”

Horizon Therapeutics is a biotechnology company focused on discovering, developing, and marketing medicines for rare, autoimmune, and severe inflammatory diseases.

The company has 12 marketed medicines and a pipeline with more than 20 development programmes, with office locations across four continents and more than 2,000 employees.

Amgen said that the acquisition will add a complementary portfolio of medicines from Horizon that will strengthen its portfolio of advanced therapeutics.

It will also generate cash flow to support capital allocation priorities, advance revenue growth, and increase efficiency for the combined group.

Amgen chairman and chief executive officer Robert A Bradway said: “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.

“Amgen’s decades of leadership in inflammation and nephrology, combined with our global presence and world-class biologics capabilities, will enable us to reach many more patients with first-in-class medicines like TEPEZZA, KRYSTEXXA and UPLIZNA.

“Additionally, the potential new medicines in Horizon’s pipeline strongly complement our R&D portfolio. The acquisition of Horizon will drive growth in Amgen’s revenue and non-GAAP EPS and is expected to be accretive from 2024.”

Morgan Stanley and JP Morgan served as financial advisors, while Cooley and Matheson as legal advisors to Horizon on the transaction.

PJT Partners served as a lead financial advisor, Citigroup as a financial advisor and Sullivan & Cromwell and William Fry as legal advisors to Amgen.

Earlier this year, Amgen signed an agreement to acquire ChemoCentryx, a company focused on treatments for rare and orphan diseases, for about $3.7bn.