NOT FOR RELEASE, PUBLICATION OR DISTRIBUTION, DIRECTLY OR INDIRECTLY, IN WHOLE OR IN PART, IN, INTO OR FROM ANY JURISDICTION WHERE TO DO SO WOULD CONSTITUTE A VIOLATION OF THE RELEVANT LAWS OR REGULATIONS OF SUCH JURISDICTION

FOR IMMEDIATE RELEASE

October 6, 2023

RECOMMENDED CASH OFFER

for

HORIZON THERAPEUTICS PLC

by

Pillartree Limited, a private limited company wholly owned by Amgen Inc.

to be implemented by way of a scheme of arrangement

under Chapter 1 of Part 9 of the Irish Companies Act 2014

Announcement relating to the Scheme becoming effective

Horizon Therapeutics plc, a public limited company incorporated in Ireland ("Horizon" or the "Company") announces that the Irish High Court-sanctioned scheme of arrangement between Horizon and its shareholders under Chapter 1 of Part 9 of the Irish Companies Act 2014 (the "Scheme") pursuant to which Pillartree Limited, a private limited company wholly owned by Amgen Inc., a Delaware corporation ("Amgen"), would acquire the entire issued ordinary share capital of Horizon (the "Acquisition"), became effective today, October 6, 2023.

Payment of the Scheme Consideration to the Scheme Shareholders pursuant to the Scheme is being commenced by Amgen today, October 6, 2023.

Trading of Horizon Shares on the Nasdaq Global Select Market ("Nasdaq") was halted with effect from 8:00 p.m. (E.T.) on October 5, 2023, will remain halted on October 6, and will be suspended effective October 9, 2023.

Certain capitalised words used in this announcement and not herein defined have the meanings given to such words in the Scheme set forth in Part 3 of the proxy statement filed by the Company with the United States Securities and Exchange Commission (the "SEC") on January 23, 2023.

Statement Required by the Irish Takeover Rules

The directors of Horizon accept responsibility for the information contained in this announcement. To the best of the knowledge and belief of the directors of Horizon (who have taken all reasonable care to ensure that such is the case), the information contained in this announcement is in accordance with the facts and does not omit anything likely to affect the import of such information.

Cautionary Statement Regarding Forward-looking Statements

This announcement contains forward-looking statements within the meaning of the Private Securities Litigation Reform Act of 1995. These forward-looking statements are often identified by words such as "anticipate," "believe," "intend," "estimate," "expect," "see," "continue," "could," "can," "may," "will," "likely," "depend," "should," "would," "plan," "predict," "target," and similar expressions, and may include references to assumptions and relate to the Acquisition. Such forward-looking statements include, but are not limited to, statements relating to the timing of payments and other post-closing actions pursuant to the Acquisition. Horizon’s expectations and beliefs regarding these matters may not materialize. Actual outcomes and results may differ materially from those contemplated by these forward-looking statements as a result of uncertainties, risks, and changes in circumstances, including but not limited to risks and uncertainties related to the outcome of any legal proceedings that have or may be instituted against the parties or any of their respective directors or officers related to the Acquisition. Additional risks and uncertainties that could cause actual outcomes and results to differ materially from those contemplated by the forward-looking statements are included under the caption "Risk Factors" and elsewhere in Horizon’s most recent filings with the SEC, including its Annual Report on Form 10-K for the year ended December 31, 2022, and any subsequent reports on Form 10-K, Form 10-Q or Form 8-K filed with the SEC from time to time and available at www.sec.gov. The forward-looking statements set out in this announcement are made only as of the date hereof. Horizon assumes no obligation and does not intend to update these forward-looking statements, except as required by law.

View source version on businesswire.com: https://www.businesswire.com/news/home/20231006256107/en/