Unless otherwise indicated or the context otherwise requires, references to “Horizon”, the “Company”, “we”, “us” and “our” refer to Horizon Therapeutics plc and its consolidated subsidiaries.

On December 12, 2022, the Company announced that it had entered into a transaction agreement with Amgen Inc. (“Amgen”) and Pillartree Limited (“Pillartree”), a wholly owned subsidiary of Amgen. Subject to the terms of the transaction agreement, Pillartree will acquire the Company (the “Transaction”), pursuant to a scheme of arrangement under Chapter 1 of Part 9 of the Companies Act 2014 of Ireland (the “Scheme”), or under certain circumstances, subject to the terms of the transaction agreement, a takeover offer (as such term is defined under the Irish Takeover Rules). As a result of the Scheme, the Company would become a wholly owned subsidiary of Amgen.

At the effective time of the Scheme (the “Effective Time”), holders of the Company’s ordinary shares will be entitled to receive $116.50 in cash per ordinary share (the “Consideration”). The Company’s equity awards will be treated as set forth in the transaction agreement, such that:

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each option to purchase the Company’s ordinary shares that is outstanding as of immediately prior to the Effective Time (whether or not vested) will, contingent upon and effective as of the Effective Time, be canceled and converted into the right to receive cash, without interest, in an amount equal to (a) the total number of the Company’s ordinary shares subject to such option immediately prior to the Effective Time, multiplied by (b) the excess of (i) the Consideration over (ii) the exercise price payable per share under such option;

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each of the Company’s restricted stock unit, or RSU, awards, excluding PSUs (as defined below), that is outstanding as of immediately prior to the Effective Time (whether or not vested) will, contingent upon and effective as of the Effective Time, (a) if granted to a non-employee member of the Company’s board of directors or held by a person who, as of the date of the completion of the Transaction, is a former service-provider of the Company, be canceled and converted into the right to receive a cash amount equal to (i) the total number of the Company’s ordinary shares subject to such RSU immediately prior to the Effective Time multiplied by (ii) the Consideration, and (b) if not granted to an individual described in clause (a) above, be canceled and converted into a restricted stock unit (an “Amgen RSU”), denominated in shares of Amgen’s common stock. The number of shares of Amgen common stock subject to each such Amgen RSU will be equal to the product (rounded down to the nearest whole number) of (a) the total number of the Company’s ordinary shares subject to such RSU immediately prior to the Effective Time multiplied by (b) the quotient of (i) the Consideration divided by (ii) the volume weighted average of the per share closing price of Amgen’s common stock on the Nasdaq Global Select Market for five trading days ending on the second business day prior to the completion of the Transaction. Following the Effective Time, each Amgen RSU will continue to be governed by the same terms and conditions (including vesting terms) as were applicable to the applicable RSU immediately prior to the Effective Time; and

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each of the Company’s RSU awards with performance-based vesting or delivery requirements, or a PSU, that is outstanding as of immediately prior to the Effective Time (whether or not vested) will, contingent upon and effective as of the Effective Time, be canceled and converted into the right to receive cash, without interest, in an amount equal to (i) the total number of the Company’s ordinary shares issuable in settlement of such PSU as determined, in accordance with the terms of such PSU, by the compensation committee of the Company’s board of directors (the “Compensation Committee”) prior to the Effective Time multiplied by (ii) the Consideration.

On February 24, 2023, the Company’s shareholders approved the Scheme and certain scheme approval resolutions and amendments to the memorandum and articles of association of Horizon to enable the Scheme to be effected. The closing of the Transaction remains subject to customary closing conditions, including, among other things, (a) the sanction by the Irish High Court of the Scheme and delivery of the court order to the Irish Registrar of Companies, (b) the receipt of required antitrust clearance in the United States, and the absence of an order or law that prevents consummation of the Transaction or imposes a burdensome condition (as defined in the transaction agreement), (c) absence of any Material Adverse Effect (as defined in the transaction agreement) from December 12, 2022 to the Sanction Date (as defined in the transaction agreement) that is continuing as of the Sanction Date, (d) the accuracy of the other party’s representations and warranties subject to certain materiality and material adverse effect exceptions and (e) the performance by each party of all of its covenants and agreements under the transaction agreement in all material respects. On January 30, 2023, the Company and Amgen received a request for additional information and documentary materials, or a second request, from the Federal Trade Commission (“FTC”) in connection with the FTC’s review of the Transaction. The effect of the second request is to extend the waiting period imposed by the Hart-Scott-Rodino Antitrust Improvements Act of 1976, as amended, until 30 days after the Company and Amgen have substantially complied with the second request, unless the period is extended voluntarily by the parties or terminated sooner by the FTC. In connection with the Transaction, the Company and Amgen have received clearances or confirmation of non-applicability related to foreign direct investment in Denmark, Italy, Germany and France and clearances related to antitrust in Germany and Austria.

The Company expects the Transaction to close during the first half of 2023, subject to the regulatory clearances and other customary closing conditions described above and in the transaction agreement.

Beginning with the third quarter of 2022, the Company separately presents upfront, milestone, and similar payments pursuant to collaborations, licenses of third-party technologies, and asset acquisitions as “Acquired in-process research and development and milestones” expenses in the consolidated statement of comprehensive income. Amounts recorded in this line item for the year ended December 31, 2022, would have historically been recorded to research and development (“R&D”) expenses. The Company believes the new classification assists users of the financial statements in better understanding the payments incurred to acquire in-process research and development (“IPR&D”). Prior period consolidated statements of comprehensive income have been reclassified to conform with the new classification. Refer to Note 2 for details on the Company’s R&D expenses and acquired IPR&D and milestones expenses accounting policies.

Horizon is a global biotechnology company focused on the discovery, development and commercialization of medicines that address critical needs for people impacted by rare, autoimmune and severe inflammatory diseases. The Company’s pipeline is purposeful: it applies scientific expertise and courage to bring clinically meaningful therapies to patients. Horizon believes science and compassion must work together to transform lives. The Company’s commercial portfolio is currently composed of 12 medicines in the areas of rare diseases, gout, ophthalmology and inflammation.

As of December 31, 2022, the Company’s commercial portfolio consisted of the following medicines: