Underwriting Agreement, dated August 6, 2020, by and among Horizon Therapeutics Public Limited Company and the several underwriters named therein

Exhibit 1.1

Execution Version

HORIZON THERAPEUTICS PUBLIC LIMITED COMPANY

11,800,000 ORDINARY SHARES, NOMINAL VALUE $0.0001 PER SHARE

UNDERWRITING AGREEMENT

August 6, 2020

Citigroup Global Markets Inc.

Morgan Stanley & Co. LLC

J.P. Morgan Securities LLC

Piper Sandler & Co.

Stifel, Nicolaus & Company, Incorporated

As Representatives of the Underwriters listed on Schedule I

388 Greenwich Street

New York, New York 10013

1585 Broadway

New York, New York 10036

383 Madison Avenue

New York, New York 10179

345 Park Avenue, 12th Floor

New York, New York 10154

787 Seventh Avenue, 11th Floor

New York, New York 10019

Ladies and Gentlemen:

Horizon Therapeutics Public Limited Company, a public limited company formed under the laws of Ireland (the “Company”), proposes to issue and sell to the several underwriters named in Schedule I hereto (the “Underwriters”), for whom you are acting as Representatives (the “Representatives”), the number of its ordinary shares, nominal value $0.0001 per share, set forth in Schedule I hereto (the “Firm Shares”). The Company also proposes to issue and sell to the several Underwriters not more than the number of additional ordinary shares of the Company, nominal value $0.0001 per share, set forth in Schedule I hereto (the “Additional Shares”) if and to the extent that you, as

Representatives of the offering, shall have determined to exercise, on behalf of the Underwriters, the right to purchase such ordinary shares granted to the Underwriters in Section 3 hereof. The Firm Shares and the Additional Shares are hereinafter collectively referred to as the “Shares.” The ordinary shares, nominal value $0.0001 per share, of the Company are hereinafter referred to as the “Ordinary Shares.”

The Company has filed with the Securities and Exchange Commission (the “Commission”) a registration statement, including a prospectus, (the file number of which is set forth in Schedule II hereto) on Form S-3, relating to the securities (the “Shelf Securities”), including the Shares, to be issued from time to time by the Company. The registration statement as amended to the date of this agreement (this “Agreement”), including the information (if any) deemed to be part of the registration statement at the time of effectiveness pursuant to Rule 430A or Rule 430B under the Securities Act of 1933, as amended (the “Securities Act”), is hereinafter referred to as the “Registration Statement”, and the related prospectus covering the Shelf Securities dated March 4, 2019 in the form first used to confirm sales of the Shares (or in the form first made available to the Underwriters by the Company to meet requests of purchasers pursuant to Rule 173 under the Securities Act) is hereinafter referred to as the “Basic Prospectus.” The Basic Prospectus, as supplemented by the prospectus supplement specifically relating to the Shares in the form first used to confirm sales of the Shares (or in the form first made available to the Underwriters by the Company to meet requests of purchasers pursuant to Rule 173 under the Securities Act) is hereinafter referred to as the “Prospectus,” and the term “preliminary prospectus” means any preliminary form of the Prospectus. For purposes of this Agreement, “free writing prospectus” has the meaning set forth in Rule 405 under the Securities Act, “Time of Sale Prospectus” means the documents and pricing information set forth opposite the caption “Time of Sale Prospectus” in Schedule II hereto, and “broadly available road show” means a “bona fide electronic road show” as defined in Rule 433(h)(5) under the Securities Act that has been made available without restriction to any person. As used herein, the terms “Registration Statement,” “Basic Prospectus,” “preliminary prospectus,” “Time of Sale Prospectus” and “Prospectus” shall include the documents, if any, incorporated by reference therein as of the date hereof. The terms “supplement,” “amendment,” and “amend” as used herein with respect to the Registration Statement, the Basic Prospectus, the Time of Sale Prospectus, any preliminary prospectus or the Prospectus shall include all documents subsequently filed by the Company with the Commission pursuant to the Securities Exchange Act of 1934, as amended (the “Exchange Act”), that are deemed to be incorporated by reference therein.

1. Representations and Warranties. The Company represents and warrants to and agrees with each of the Underwriters that:

(a) The Registration Statement has become effective; no stop order suspending the effectiveness of the Registration Statement is in effect, and no proceedings for such purpose or pursuant to Section 8A under the Securities Act are pending before or, to the Company’s knowledge, threatened by the Commission. If the Registration Statement is an automatic shelf registration statement as defined in Rule 405 under the Securities Act, the Company is a well-known seasoned issuer (as defined in Rule 405 under the

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Securities Act) eligible to use the Registration Statement as an automatic shelf registration statement and the Company has not received notice that the Commission objects to the use of the Registration Statement as an automatic shelf registration statement.

(b) (i) Each document, if any, filed or to be filed pursuant to the Exchange Act and incorporated by reference in the Time of Sale Prospectus or the Prospectus complied or will comply when so filed in all material respects with the Exchange Act and the applicable rules and regulations of the Commission thereunder, (ii) each part of the Registration Statement, when such part became effective, did not contain, and each such part, as amended or supplemented, if applicable, will not contain, as of the date of such amendment or supplement, any untrue statement of a material fact or omit to state a material fact required to be stated therein or necessary to make the statements therein not misleading, (iii) the Registration Statement as of the date hereof does not contain any untrue statement of a material fact or omit to state a material fact required to be stated therein or necessary to make the statements therein not misleading, (iv) the Registration Statement and the Prospectus comply, and as amended or supplemented, if applicable, will comply in all material respects with the Securities Act and the applicable rules and regulations of the Commission thereunder, (v) the Time of Sale Prospectus does not, and at the time of each sale of the Shares in connection with the offering when the Prospectus is not yet available to prospective purchasers and at the Closing Date (as defined in Section 4), the Time of Sale Prospectus, as then amended or supplemented by the Company, if applicable, and any individual Testing-the-Water Communication (as defined below), when considered together with the Time of Sale Prospectus, will not contain any untrue statement of a material fact or omit to state a material fact necessary to make the statements therein, in the light of the circumstances under which they were made, not misleading, (vi) each broadly available road show, if any, when considered together with the Time of Sale Prospectus, does not contain any untrue statement of a material fact or omit to state a material fact necessary to make the statements therein, in the light of the circumstances under which they were made, not misleading and (vii) the Prospectus does not contain and, as amended or supplemented, if applicable, will not contain, as of the date of such amendment or supplement, any untrue statement of a material fact or omit to state a material fact necessary to make the statements therein, in the light of the circumstances under which they were made, not misleading, except that the representations and warranties set forth in this paragraph do not apply to statements or omissions in the Registration Statement, the Time of Sale Prospectus or the Prospectus based upon information relating to any Underwriter furnished to the Company in writing by such Underwriter through the Representatives expressly for use therein.

(c) Ineligible Issuer. The Company is not an “ineligible issuer” in connection with the offering pursuant to Rules 164, 405 and 433 under the Securities Act. Any free writing prospectus that the Company is required to file pursuant to Rule 433(d) under the Securities Act has been, or will be, filed with the Commission in accordance with the requirements of the Securities Act and the applicable rules and regulations of the Commission thereunder. Each free writing prospectus that the Company has filed, or is required to file, pursuant to Rule 433(d) under the Securities Act or that was prepared by or on behalf of or used or referred to by the Company complies or will comply in all

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material respects with the requirements of the Securities Act and the applicable rules and regulations of the Commission thereunder. Except for the free writing prospectuses, if any, identified in Schedule II hereto forming part of the Time of Sale Prospectus, and electronic road shows, if any, each furnished to you before first use, the Company has not prepared, used or referred to, and will not, without your prior consent, prepare, use or refer to, any free writing prospectus.

(d) Offering Materials Furnished to Underwriters. The Company has delivered to each Representatives a complete copy of the Registration Statement and each amendment thereto and of each consent and certificate of experts filed as a part thereof, and conformed copies of the Registration Statement, each amendment thereto and preliminary prospectuses, the Time of Sale Prospectus, the Prospectus, as amended or supplemented, and any free writing prospectus reviewed and consented to by the Representatives, in such quantities and at such places as the Representatives have reasonably requested for each of the Underwriters.

(e) Distribution of Offering Material By the Company. The Company has not distributed and will not distribute, prior to the later of (i) the expiration or termination of the option granted to the several Underwriters in Section 2 and (ii) the completion of the Underwriters’ distribution of the Shares, any offering material in connection with the offering and sale of the Shares other than a preliminary prospectus, the Time of Sale Prospectus, the Prospectus, any free writing prospectus reviewed and consented to by the Representatives, or the Registration Statement.

(f) The Underwriting Agreement. This Agreement has been duly authorized, executed and delivered by, and is a valid and binding agreement of, the Company, enforceable against the Company in accordance with its terms, except as rights to indemnification hereunder may be limited by applicable law and except as the enforcement hereof may be limited by bankruptcy, insolvency, reorganization, moratorium or other similar laws relating to or affecting the rights and remedies of creditors or by general equitable principles.

(g) Authorization of the Shares. The Shares to be purchased by the Underwriters from the Company have been duly authorized for issuance and sale to the Underwriters pursuant to this Agreement and, when issued and delivered by the Company pursuant to this Agreement against payment of the consideration set forth herein, will be validly issued and fully paid and non-assessable; and the issuance of the Shares is not subject to the preemptive or other similar rights of any holder of the Company.

(h) No Applicable Registration or Other Similar Rights. There are no persons with registration or other similar rights to have any equity or debt securities registered for sale under the Registration Statement or included in the offering contemplated by this Agreement, except for such rights as have been duly waived or complied with.

(i) No Material Adverse Change. Except as otherwise disclosed in the Time of Sale Prospectus, subsequent to the respective dates as of which information is given in

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the Time of Sale Prospectus: (i) there has been no material adverse change, or any development that could reasonably be expected to result in a material adverse change, in the condition, financial or otherwise, or in the earnings, business, operations or prospects, whether or not arising from transactions in the ordinary course of business, of the Company and its subsidiaries, considered as one entity (any such change is called a “Material Adverse Change”); (ii) the Company and its subsidiaries, considered as one entity, have not incurred any material liability or obligation, indirect, direct or contingent, not in the ordinary course of business nor entered into any material transaction or agreement not in the ordinary course of business; and (iii) there has been no dividend or distribution of any kind declared, paid or made by the Company or, except for dividends paid to the Company or other subsidiaries, any of its subsidiaries on any class of capital stock or repurchase or redemption by the Company or any of its subsidiaries of any class of capital stock.

(j) Independent Registered Public Accounting Firms. PricewaterhouseCoopers LLP, which has expressed its opinion with respect to the financial statements of the Company (which term as used in this Agreement includes the related notes thereto) and supporting schedules filed with the Commission and included or incorporated by reference in the Registration Statement and the preliminary prospectus, the Prospectus and Time of Sale Prospectus (each, an “Applicable Prospectus” and collectively, the “Applicable Prospectuses”), is (i) an independent registered public accounting firm as required by the Securities Act and the Exchange Act, (ii) in compliance with the applicable requirements relating to the qualification of accountants under Rule 2-01 of Regulation S-X and (iii) an independent registered public accounting firm as defined by the Public Company Accounting Oversight Board (the “PCAOB”) whose registration has not been suspended or revoked and, to the Company’s knowledge, who has not requested such registration to be withdrawn.

(k) Preparation of the Financial Statements.

(i) The financial statements of the Company filed with the Commission and incorporated by reference in the Registration Statement, the Time of Sale Prospectus and the Prospectus (the “Company Financial Statements”) present fairly, in all material respects, the consolidated financial position of the Company and its subsidiaries as of and at the dates indicated and the results of their operations and cash flows for the periods specified. The supporting schedules to such Company Financial Statements included or incorporated by reference in the Registration Statement and the Time of Sale Prospectus and the Prospectus present fairly, in all material respects, the information required to be stated therein. Such Company Financial Statements and supporting schedules have been prepared in conformity with generally accepted accounting principles, as applied in the United States, applied on a consistent basis throughout the periods involved, except as may be expressly stated in the related notes thereto.

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(ii) No financial statements or supporting schedules are required to be included in the Registration Statement or any Applicable Prospectus which are not so included.

(iii) To the Company’s knowledge, no person who has been suspended or barred from being associated with a registered public accounting firm, or who has failed to comply with any sanction pursuant to Rule 5300 promulgated by the PCAOB, has participated in or otherwise aided the preparation of, or audited, the financial statements, supporting schedules or other financial data filed with the Commission as a part of the Registration Statement and any Applicable Prospectus.

(l) Interactive Data. The interactive data in eXtensible Business Reporting Language included or incorporated by reference in the Registration Statement fairly presents the information called for in all material respects and has been prepared in accordance with the Commission’s rules and guidelines applicable thereto.

(m) Internal Control Over Financial Reporting. The Company and each of its subsidiaries make and keep books and records that are accurate in all material respects. The Company maintains a system of internal control over financial reporting (as such term is defined in Exchange Act Rule 13a-15(f)) that complies with the requirements of the Exchange Act (as defined below) applicable to the Company and has been designed by the Company’s principal executive officer and principal financial officer, or under their supervision, to provide reasonable assurance regarding the reliability of financial reporting and the preparation of financial statements for external purposes in accordance with U.S. generally accepted accounting principles. The Company is not aware of (i) any material weakness or significant deficiency in the Company’s internal control over financial reporting (it being understood that this subsection shall not require the Company to comply with Section 404 of the Sarbanes Oxley Act of 2002 as of an earlier date than it would otherwise be required to so comply under applicable law) except as has not resulted or is not expected to result in any changes to the Company’s financial statements other than those disclosed in the Time of Sale Prospectus or (ii) any fraud, whether or not material, that involves management or other employees who have a significant role in the Company’s internal control over financial reporting. Except as disclosed in the Time of Sale Prospectus, since the date of the latest quarterly or annual financial statements included or incorporated by reference in the Time of Sale Prospectus, there has been no change in the Company’s internal control over financial reporting that has materially affected, or is reasonably likely to materially affect, the Company’s internal control over financial reporting.

(n) Incorporation and Good Standing of the Company and its Subsidiaries. Each of the Company and its subsidiaries has been duly incorporated or organized, as the case may be, and is validly existing as a public limited company, corporation, partnership or limited liability company, as applicable, in good standing (if applicable) under the laws of the jurisdiction of its incorporation or organization and has the power and authority (corporate or other) to own, lease and operate its properties and to conduct its business as described in each Applicable Prospectus and, in the case of the Company, to

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enter into and perform its obligations under this Agreement, except where the failure to be in good standing would not reasonably be expected to result in a Material Adverse Change. Each of the Company and each subsidiary is duly qualified as a foreign corporation, partnership or limited liability company, as applicable, to transact business and is in good standing (if applicable) in each other jurisdiction in which such qualification is required, whether by reason of the ownership or leasing of property or the conduct of business, except where the failure to be so qualified or in good standing would not reasonably be expected to result in a Material Adverse Change. All of the issued and outstanding capital stock or other equity or ownership interests of each of the Company’s subsidiaries have been duly authorized and validly issued, are fully paid and non-assessable and, except as set forth in the Time of Sale Prospectus, are owned by the Company, directly or through subsidiaries, free and clear of any security interest, mortgage, pledge, lien, encumbrance or adverse claim. The Company does not own or control, directly or indirectly, any corporation, association or other entity other than (i) the subsidiaries listed in Exhibit 21.1 to the Company’s Form 10-K for the fiscal year ended December 31, 2019 and (ii) such other entities omitted from Exhibit 21.1 which, when such omitted entities are considered in the aggregate as a single subsidiary, would not constitute a “significant subsidiary” within the meaning of Rule 1-02(w) of Regulation S-X.

(o) Capitalization and Other Capital Stock Matters. Since the most recent date such information was included in the Prospectus, there has been no material change in the authorized, issued and outstanding capital stock of the Company (other than for subsequent issuances, if any, pursuant to employee benefit plans described in the Time of Sale Prospectus, upon the exercise of outstanding options or warrants described in the Time of Sale Prospectus, upon settlement of outstanding restricted stock units described in the Time of Sale Prospectus or as otherwise described in any document incorporated by reference in the Prospectus). The Ordinary Shares (including the Shares) conform in all material respects to the description thereof contained in the Time of Sale Prospectus. All of the issued and outstanding Ordinary Shares have been duly authorized and validly issued, are fully paid and non-assessable and have been issued in compliance with federal and state securities laws. None of the outstanding Ordinary Shares were issued in violation of any preemptive rights, rights of first refusal or other similar rights to subscribe for or purchase securities of the Company. The Company has sufficient authorized but unissued share capital to issue the Shares and all necessary approvals and authorities have been granted or obtained to allot and issue the Shares to the Underwriters. Except as may have been issued pursuant to the Company’s stock option and other stock plans or arrangements described in the Time of Sale Prospectus, there are no authorized or outstanding options, warrants, preemptive rights, rights of first refusal or other rights to purchase, or equity or debt securities convertible into or exchangeable or exercisable for, any capital stock of the Company or any of its subsidiaries other than those accurately described in the Time of Sale Prospectus. The description of the Company’s stock option, stock bonus and other stock plans or arrangements, and the options or other rights granted thereunder, set forth in each Applicable Prospectus accurately and fairly presents, in all material respects, the information required to be shown with respect to such plans, arrangements, options and rights. All grants of options

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to acquire Ordinary Shares (each, a “Company Stock Option”) were validly assumed or issued and approved by the Board of Directors of the Company, a committee thereof or an individual with authority duly delegated by the Board of Directors of the Company or a committee thereof. Grants of Company Stock Options were (i) made in material compliance with all applicable laws and (ii) as a whole, made in material compliance with the terms of the plans under which such Company Stock Options were issued. Except as disclosed in or contemplated by the Time of Sale Prospectus, there is no and has been no policy or practice of the Company to coordinate the grant of Company Stock Options with the release or other public announcement of material information regarding the Company or its results of operations or prospects.

(p) Stock Exchange Listing. The Shares are approved for listing on the Nasdaq Global Select Market.

(q) Non-Contravention of Existing Instruments; No Further Authorizations or Approvals Required. Neither the Company nor any of its subsidiaries is in violation of its charter or bylaws, partnership agreement or operating agreement or similar organizational document, as applicable, or is in default (or, with the giving of notice or lapse of time, would be in default) (“Default”) under any indenture, mortgage, loan or credit agreement, note, contract, franchise, lease or other instrument to which the Company or any of its subsidiaries is a party or by which it or any of them may be bound (including, without limitation, any credit agreement, indenture, pledge agreement, security agreement or other instrument or agreement evidencing, guaranteeing, securing or relating to indebtedness of the Company or any of its subsidiaries), or to which any of the property or assets of the Company or any of its subsidiaries is subject (each, an “Existing Instrument”), except for such Defaults as would not reasonably be expected to, individually or in the aggregate, result in a Material Adverse Change. The Company’s execution, delivery and performance of this Agreement, consummation of the transactions contemplated hereby and by the Prospectus, and the sale of the Shares by the Company (i) have been duly authorized by all necessary corporate action of the Company and will not result in any violation of the provisions of the charter or bylaws, partnership agreement or operating agreement or similar organizational document of the Company or any subsidiary, as applicable, (ii) will not conflict with or constitute a breach of, or Default under, or result in the creation or imposition of any lien, charge or encumbrance upon any property or assets of the Company or any of its subsidiaries pursuant to, or require the consent of any other party to, any Existing Instrument, except for such breaches, Defaults or results, or failure to obtain such consent, as would not reasonably be expected, individually or in the aggregate, to result in a Material Adverse Change and (iii) will not, assuming the Underwriters’ compliance with their obligations under this Agreement, result in any violation of any law, administrative regulation or administrative or court decree applicable to the Company or any subsidiary, except for such violations as would not reasonably be expected, individually or in the aggregate, to result in a Material Adverse Change. No consent, approval, authorization or other order of, or registration or filing with, any court or other governmental or regulatory authority or agency, is required for the Company’s execution, delivery and performance of this Agreement and the Company’s consummation of the transactions contemplated hereby and by the Prospectus, except such as have been obtained or made or will be made by the

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Company under the Securities Act, or that may be required under applicable state securities or blue sky laws, Irish laws and from the Financial Industry Regulatory Authority (“FINRA”).

(r) No Material Actions or Proceedings. Except as disclosed in the Time of Sale Prospectus, there are no legal or governmental actions, suits or proceedings pending or, to the Company’s knowledge, threatened (i) against or affecting the Company or any of its subsidiaries, (ii) which have as the subject thereof any officer or director of, or property owned or leased by, the Company or any of its subsidiaries or (iii) relating to environmental or discrimination matters, where in any such case (A) to the Company’s knowledge there is a substantial likelihood that such action, suit or proceeding will be determined adversely to the Company, such subsidiary or such officer or director, (B) any such action, suit or proceeding, if so determined adversely, would reasonably be expected to result in a Material Adverse Change or adversely affect the consummation of the transactions contemplated by this Agreement or (C) any such action, suit or proceeding is or would be material in the context of the sale of the Shares. No material labor dispute with the employees of the Company or any of its subsidiaries, exists or, to the Company’s knowledge, is threatened or imminent.

(s) Intellectual Property Rights. The Company and its subsidiaries own, possess or can acquire on reasonable terms sufficient trademarks, trade names, patent rights, copyrights, domain names, licenses, approvals, trade secrets and other similar rights (collectively, “Intellectual Property Rights”) reasonably necessary to conduct their businesses as now conducted; except to the extent failure to own, possess or acquire such Intellectual Property Rights would not result in a Material Adverse Change. Neither the Company nor any of its subsidiaries has received, or has any reason to believe that it will receive, any notice of infringement or conflict with asserted Intellectual Property Rights of others. Except as would not be reasonably likely to result, individually or in the aggregate, in a Material Adverse Change or except as disclosed in the Time of Sale Prospectus (i) to the Company’s knowledge, there is no infringement, misappropriation or violation by third parties of any of the Intellectual Property Rights owned by the Company; (ii) there is no pending or, to the Company’s knowledge, threatened action, suit, proceeding or claim by others challenging the rights of the Company and its subsidiaries in or to any such Intellectual Property Rights, and the Company is unaware of any facts which would form a reasonable basis for any such claim, that would, individually or in the aggregate, together with any other claims in this subsection (r) result in a Material Adverse Change; (iii) the Intellectual Property Rights owned by the Company and its subsidiaries and, to the Company’s knowledge, the Intellectual Property Rights licensed to the Company and its subsidiaries have not been adjudged by a court of competent jurisdiction invalid or unenforceable, in whole or in part, and there is no pending or, to the Company’s knowledge, threatened action, suit, proceeding or claim by others challenging the validity or scope of any such Intellectual Property Rights, and the Company is unaware of any facts which would form a reasonable basis for any such claim that would, individually or in the aggregate, together with any other claims in this subsection (r) result in a Material Adverse Change; (iv) there is no pending or, to the Company’s knowledge, threatened action, suit, proceeding or claim by others that the Company or its subsidiaries infringe, misappropriate or otherwise violate any Intellectual

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Property Rights or other proprietary rights of others, the Company and its subsidiaries have not received any written notice of such claim and the Company is unaware of any other facts which would form a reasonable basis for any such claim that would reasonably be expected, individually or in the aggregate, together with any other claims in this subsection (r) to result in a Material Adverse Change; and (v) to the Company’s knowledge, no employee of the Company or a subsidiary of the Company is in or has ever been in violation in any material respect of any term of any employment contract, patent disclosure agreement, invention assignment agreement, non-competition agreement, non-solicitation agreement, nondisclosure agreement or any restrictive covenant to or with a former employer where the basis of such violation relates to such employee’s employment with the Company or a subsidiary of the Company, or actions undertaken by the employee while employed with the Company or a subsidiary of the Company and would reasonably be expected to result, individually or in the aggregate, in a Material Adverse Change. To the Company’s knowledge, all material technical information developed by and belonging to the Company and its subsidiaries for which they have not sought, and do not intend to seek, to patent or otherwise protect pursuant to applicable intellectual property laws has been kept confidential or disclosed only under obligations of confidentiality. The Company is not a party to or bound by any options, licenses or agreements with respect to the Intellectual Property Rights of any other person or entity that are required to be set forth in the Prospectus and are not described therein. None of the technology employed by the Company or any of its subsidiaries has been obtained or is being used by the Company or any of its subsidiaries in violation of any contractual obligation binding on the Company or any of its subsidiaries or, to the Company’s knowledge, any of its or its subsidiaries’ officers, directors or employees or otherwise in violation of the rights of any persons, except in each case for such violations that would not reasonably be expected to result in a Material Adverse Change.

(t) All Necessary Permits, etc. The Company and each subsidiary possess such valid and current certificates, authorizations or permits issued by the appropriate state, federal or foreign regulatory agencies or bodies necessary to conduct their respective businesses other than those the failure to possess or own would not result in a Material Adverse Change, and neither the Company nor any subsidiary has received, or has any reason to believe that it will receive, any notice of proceedings relating to the revocation or modification of, or non-compliance with, any such certificate, authorization or permit which, singly or in the aggregate, if the subject of an unfavorable decision, ruling or finding, would reasonably be expected to result in a Material Adverse Change.

(u) Title to Properties. The Company and each of its subsidiaries has good and marketable title to all of the real and personal property and other assets owned by it, in each case free and clear of any security interests, mortgages, liens, encumbrances, equities, adverse claims and other defects, except such as are disclosed in the Time of Sale Prospectus or as do not materially and adversely affect the value of such property and do not materially interfere with the use made or proposed to be made of such property by the Company or such subsidiary. To the Company’s knowledge, the real property, improvements, equipment and personal property held under lease by the Company or any subsidiary are held under valid and enforceable leases, with such exceptions as are not material and do not materially interfere with the use made or

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proposed to be made of such real property, improvements, equipment or personal property by the Company or such subsidiary.

(v) Tax Law Compliance. The Company and its consolidated subsidiaries have filed all necessary U.S. federal and state, Irish and other corporation, income and franchise tax returns or have properly requested extensions thereof and have paid all taxes required to be paid by any of them and, if due and payable, any related or similar assessment, fine or penalty levied against any of them except as may be being contested in good faith and by appropriate proceedings. The Company has made adequate charges, accruals and reserves in the applicable financial statements of the Company referred to in Section 1(k) above in respect of all U.S. federal and state, Irish and other income and franchise taxes for all periods as to which the tax liability of the Company or any of its consolidated subsidiaries has not been finally determined.

(w) Company Not an “Investment Company”. The Company has been advised of the rules and requirements under the Investment Company Act of 1940, as amended (the “Investment Company Act”). The Company is not an “investment company” within the meaning of the Investment Company Act and will conduct its business in a manner so that it will not become subject to the Investment Company Act.

(x) Insurance. Each of the Company and its subsidiaries are insured by recognized, financially sound and reputable institutions with policies in such amounts and with such deductibles and covering such risks as are generally deemed adequate and customary for the business for which it is engaged. The Company has no reason to believe that it or any subsidiary will not be able (i) to renew its existing insurance coverage as and when such policies expire or (ii) to obtain comparable coverage from similar institutions as may be necessary or appropriate to conduct its business as now conducted and at a cost that would not result in a Material Adverse Change. Neither the Company nor any subsidiary has been denied any insurance coverage material to the Company which it has sought or for which it has applied.

(y) No Price Stabilization or Manipulation; Compliance with Regulation M. The Company has not taken and will not take, directly or indirectly, any action designed to or that might be reasonably expected to cause or result in stabilization or manipulation of the price of the Shares or any other “reference security” (as defined in Rule 100 of Regulation M under the Exchange Act (“Regulation M”)) whether to facilitate the sale or resale of the Shares or otherwise, and has taken no action which would directly or indirectly violate Regulation M. The Company acknowledges that the Underwriters may engage in passive market making transactions in the Shares on the Nasdaq Global Select Market in accordance with Regulation M.

(z) Related Party Transactions. There are no business relationships or related-party transactions involving the Company or any of its subsidiaries or any other person required to be described in each Applicable Prospectus which have not been described as required, except as disclosed in the definitive Proxy Statement filed by the Company in connection with its 2020 Annual General Meeting of Shareholders.

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(aa) FINRA Matters. All of the information provided to the Underwriters or to counsel for the Underwriters by the Company, its officers and directors and the holders of any securities (debt or equity) or options to acquire any securities of the Company in connection with any letters, filings or other supplemental information provided to FINRA pursuant to FINRA Rule 5110 or FINRA Rule 5121 is true, complete and correct.

(bb) Parties to Lock-Up Agreements. Each of the Company’s directors and officers listed in Exhibit B hereto has executed and delivered to the Representatives a lock-up agreement substantially in the form of Exhibit A hereto. Exhibit B hereto contains a true, complete and correct list of all directors and officers of the Company. If any additional persons shall become directors or officers of the Company prior to the end of the Restricted Period (as defined below), the Company shall cause each such person, prior to or contemporaneously with their appointment or election as a director or officer of the Company, to execute and deliver to the Representatives an agreement substantially in the form attached hereto as Exhibit A. For purposes of this Section 1(bb), the term “officers” shall mean those officers contemplated by Rule 16a-1(f) under the Exchange Act.

(cc) Statistical and Market-Related Data. The statistical, demographic and market-related data included in the Registration Statement and each Applicable Prospectus are based on or derived from sources that the Company believes to be reliable and accurate or represent the Company’s good faith estimates that are made on the basis of data derived from such sources.

(dd) Disclosure Controls and Procedures. The Company maintains a system of accounting controls sufficient to provide reasonable assurances that (i) transactions are executed in accordance with management’s general or specific authorization; (ii) transactions are recorded as necessary to permit preparation of financial statements in conformity with generally accepted accounting principles as applied in the United States and to maintain accountability for assets; (iii) access to assets is permitted only in accordance with management’s general or specific authorization; and (iv) the recorded accountability for assets is compared with existing assets at reasonable intervals and appropriate action is taken with respect to any differences. The Company has established and maintains disclosure controls and procedures (as defined in Exchange Act Rules 13a-15(e) and 15d-15(e)), which (i) are designed to ensure that material information relating to the Company, including its consolidated subsidiaries, is made known to the Company’s principal executive officer and its principal financial officer by others within those entities, during the periods in which the periodic reports required under the Exchange Act are being prepared; (ii) have been evaluated by management of the Company for effectiveness as of the end of the Company’s fiscal year ended December 31, 2019; and (iii) are effective in all material respects to perform the functions for which they were established.

(ee) Compliance with Environmental Laws. Except as described in the Time of Sale Prospectus and except as would not reasonably be expected to, individually or in the aggregate, result in a Material Adverse Change: (i) neither the Company nor any of its subsidiaries is in violation of any federal, state, local or foreign law or regulation relating

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to pollution or protection of human health or the environment (including, without limitation, ambient air, surface water, groundwater, land surface or subsurface strata) or wildlife, including without limitation, laws and regulations relating to emissions, discharges, releases or threatened releases of chemicals, pollutants, contaminants, wastes, toxic substances, hazardous substances, petroleum and petroleum products (collectively, “Materials of Environmental Concern”), or otherwise relating to the manufacture, processing, distribution, use, treatment, storage, disposal, transport or handling of Materials of Environmental Concern (collectively, “Environmental Laws”), which violation includes, but is not limited to, noncompliance with any permits or other governmental authorizations required for the operation of the business of the Company or its subsidiaries under applicable Environmental Laws, or noncompliance with the terms and conditions thereof, nor has the Company or any of its subsidiaries received any written communication, whether from a governmental authority, citizens group, employee or otherwise, that alleges that the Company or any of its subsidiaries is in violation of any Environmental Law; (ii) there is no claim, action or cause of action filed with a court or governmental authority, no investigation with respect to which the Company has received written notice, and no written notice by any person or entity alleging potential liability for investigatory costs, cleanup costs, governmental responses costs, natural resources damages, property damages, personal injuries, attorneys’ fees or penalties arising out of, based on or resulting from the presence, or release into the environment, of any Material of Environmental Concern at any location owned, leased or operated by the Company or any of its subsidiaries, now or in the past (collectively, “Environmental Claims”), pending or, to the Company’s knowledge, threatened against the Company or any of its subsidiaries or any person or entity whose liability for any Environmental Claim the Company or any of its subsidiaries has retained or assumed either contractually or by operation of law; and (iii) to the Company’s knowledge, there are no past or present actions, activities, circumstances, conditions, events or incidents, including, without limitation, the release, emission, discharge, presence or disposal of any Material of Environmental Concern, that reasonably could result in a violation of any Environmental Law or form the basis of a potential Environmental Claim against the Company or any of its subsidiaries or against any person or entity whose liability for any Environmental Claim the Company or any of its subsidiaries has retained or assumed either contractually or by operation of law.

(ff) ERISA Compliance. The Company and its subsidiaries and any “employee benefit plan” (as defined under the Employee Retirement Income Security Act of 1974, as amended, and the regulations and published interpretations thereunder (collectively, “ERISA”)) established or maintained by the Company, its subsidiaries or their “ERISA Affiliates” (as defined below) are in compliance in all material respects with ERISA. “ERISA Affiliate” means, with respect to the Company or a subsidiary, any member of any group of organizations described in Sections 414(b), (c), (m) or (o) of the Internal Revenue Code of 1986, as amended, and the regulations and published interpretations thereunder (the “Code”) of which the Company or such subsidiary is a member. No “reportable event” (as defined under ERISA) has occurred or is reasonably expected to occur with respect to any “employee benefit plan” established or maintained by the Company, its subsidiaries or any of their ERISA Affiliates. No “employee benefit plan”

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established or maintained by the Company, its subsidiaries or any of their ERISA Affiliates, if such “employee benefit plan” were terminated, would have any “amount of unfunded benefit liabilities” (as defined under ERISA). Neither the Company, its subsidiaries nor any of their ERISA Affiliates has incurred or reasonably expects to incur any liability under (i) Title IV of ERISA with respect to termination of, or withdrawal from, any “employee benefit plan” or (ii) Sections 412, 4971, 4975 or 4980B of the Code. Each “employee benefit plan” established or maintained by the Company, its subsidiaries or any of their ERISA Affiliates that is intended to be qualified under Section 401(a) of the Code is so qualified and nothing has occurred, whether by action or failure to act, which would reasonably be expected to result in the loss of such qualification.

(gg) Brokers. Except as contemplated by this Agreement, there is no broker, finder or other party that is entitled to receive from the Company any brokerage or finder’s fee or other fee or commission as a result of any transactions contemplated by this Agreement.

(hh) No Outstanding Loans or Other Extensions of Credit. There are no outstanding loans, advances (except normal advances for business expenses in the ordinary course of business) or guarantees or indebtedness by the Company to or for the benefit of any of the executive officers or directors of the Company or any of the family members of any of them, except in each case as would not violate Section 13(k) of the Exchange Act.

(ii) Compliance with Laws. The Company has not been advised, and has no reason to believe, that it or any of its subsidiaries has conducted business in compliance with all applicable laws, rules and regulations of the jurisdictions in which it is conducting business, except where failure to be so in compliance would not result in a Material Adverse Change. The Company has not received any FDA Form 483, notice of adverse finding, warning letter, untitled letter or other correspondence or notice from the U.S. Food and Drug Administration or any other governmental authority alleging or asserting noncompliance with any laws applicable to the Company.

(jj) Dividend Restrictions. Except as described in the Time of Sale Prospectus or provided under credit facility agreements filed as exhibits to documents incorporated by reference in the Registration Statement, and except for any U.S. state or foreign law restriction on the payment of dividends, no subsidiary of the Company is prohibited or restricted, directly or indirectly, from paying dividends to the Company, or from making any other distribution with respect to such subsidiary’s equity securities or from repaying to the Company or any other subsidiary of the Company any amounts that may from time to time become due under any loans or advances to such subsidiary from the Company or from transferring any property or assets to the Company or to any other subsidiary.

(kk) No Reliance. The Company has not relied upon the Underwriters or legal counsel for the Underwriters for any legal, tax or accounting advice in connection with the offering and sale of the Shares.

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(ll) No Unlawful Payments. Neither the Company nor any of its subsidiaries, nor any director or officer of the Company or of any of its subsidiaries, nor, to the knowledge of the Company, any agent, employee, affiliate or other person acting on behalf of the Company or any of its subsidiaries has taken any action in furtherance of an offer, payment, promise to pay, or authorization or approval of the payment, giving or receipt of money, property, gifts or anything else of value, directly or indirectly, to any government official (including any officer or employee of a government or government-owned or controlled entity or of a public international organization, or any person acting in an official capacity for or on behalf of any of the foregoing, or any political party or party official or candidate for political office) in order to influence official action, or to any person in violation of any applicable anti-corruption laws; (ii) the Company and each of its subsidiaries and affiliates have conducted their businesses in compliance with applicable anti-corruption laws and have instituted and maintained policies and procedures reasonably designed to promote and achieve, and which are reasonably expected to continue to promote and achieve, compliance with such laws and with the representations and warranties contained herein; and (iii) neither the Company nor any of its subsidiaries will use, directly or indirectly, the proceeds of the offering in furtherance of an offer, payment, promise to pay, or authorization of the payment or giving of money, or anything else of value, to any person in violation of any applicable anti-corruption laws.

(mm) Money Laundering Laws. The operations of the Company and each of its subsidiaries are and have been conducted at all times in material compliance with all applicable financial recordkeeping and reporting requirements, including those of the Bank Secrecy Act, as amended by Title III of the Uniting and Strengthening America by Providing Appropriate Tools Required to Intercept and Obstruct Terrorism Act of 2001 (USA PATRIOT Act), and the applicable anti-money laundering statutes of jurisdictions where the Company and each of its subsidiaries conduct business, the rules and regulations thereunder and any related or similar rules, regulations or guidelines, issued, administered or enforced by any governmental agency (collectively, the “Anti-Money Laundering Laws”), and no action, suit or proceeding by or before any court or governmental agency, authority or body or any arbitrator involving the Company or any of its subsidiaries with respect to the Anti-Money Laundering Laws is pending or, to the best knowledge of the Company, threatened.

(nn) OFAC. (i) Neither the Company nor any of its subsidiaries, nor any director or officer of the Company or of any of its subsidiaries, nor, to the knowledge of the Company, any agent, employee or affiliate of the Company or any of its subsidiaries:

(A) is, or is controlled or 50% or more owned in the aggregate by or is acting on behalf of, one or more individuals or entities that are currently the subject of any sanctions administered or enforced by the United States (including any administered or enforced by the Office of Foreign Assets Control of the U.S. Department of the Treasury, the U.S. Department of State or the Bureau of Industry and Security of the U.S. Department of Commerce), the United Nations Security Council, the European Union, a member state of the European Union (including

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sanctions administered or enforced by Her Majesty’s Treasury of the United Kingdom) or other relevant sanctions authority (collectively, “Sanctions” and such persons, “Sanctioned Persons” and each such person, a “Sanctioned Person”),

(B) is located, organized or resident in a country or territory that is, or whose government is, the subject of Sanctions that broadly prohibit dealings with that country or territory (collectively, “Sanctioned Countries” and each, a “Sanctioned Country”), or

(C) will, directly or indirectly, use the proceeds of this offering, or lend, contribute or otherwise make available such proceeds to any subsidiary, joint venture partner or other individual or entity in any manner that would result in a violation of any Sanctions by, or could result in the imposition of Sanctions against, any individual or entity (including any individual or entity participating in the offering, whether as underwriter, advisor, investor or otherwise).

(ii) For the past five years, none of the Company or any of its subsidiaries have knowingly engaged in and are not now knowingly engaged in any dealings or transactions with any individual or entity that at the time of the dealing or transaction is or was the subject or the target of Sanctions.

(oo) PFIC Status. Based on the current projections regarding the composition of the Company’s income and valuation of its assets and operations and subject to the qualifications and limitations set forth in the Time of Sale Prospectus, the Company does not expect to be a “passive foreign investment company,” as defined in Section 1297 of the Code, for its current taxable year or subsequent taxable years.

(pp) Cybersecurity.

(i) (A) The Company and each of its subsidiaries have complied and are presently in compliance with all internal and external privacy policies, contractual obligations, industry standards, applicable laws, statutes, judgments, orders, rules and regulations of any court or arbitrator or other governmental or regulatory authority and any other legal obligations, in each case, relating to the collection, use, transfer, import, export, storage, protection, disposal and disclosure by the Company or any of its subsidiaries of personal, personally identifiable, household, sensitive, confidential or regulated data (“Data Security Obligations”, and such data, “Data”); (B) the Company has not received any notification of or complaint regarding and is unaware of any other facts that, individually or in the aggregate, would reasonably indicate non-compliance with any Data Security Obligation; and (C) of there is no action, suit or proceeding by or before any court or governmental agency, authority or body pending or threatened alleging non-compliance with any Data Security Obligation, except in each case as would not result in a Material Adverse Change.

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(ii) The Company and each of its subsidiaries have taken reasonable technical and organizational measures to protect the information technology systems and Data used in connection with the operation of the Company’s and its subsidiaries’ businesses. Without limiting the foregoing, the Company and its subsidiaries have used reasonable efforts to establish and maintain, and have established, maintained, implemented and complied with, reasonable information technology, information security, cyber security and data protection controls, policies and procedures, including oversight, access controls, encryption, technological and physical safeguards and business continuity/disaster recovery and security plans that are designed to protect against and prevent breach, destruction, loss, unauthorized distribution, use, access, disablement, misappropriation or modification, or other compromise or misuse of or relating to any information technology system or Data used in connection with the operation of the Company’s and its subsidiaries’ businesses (“Breach”). There has been no such Breach, and the Company and its subsidiaries have not been notified of and have no knowledge of any event or condition that would reasonably be expected to result in, any such Breach, except for any such Breach as would not result in a Material Adverse Change.

(qq) Taxes. There are no transfer taxes, stamp duty or other similar fees or charges under Irish or U.S. federal law or the laws of any U.S. state, or any political subdivision thereof, required to be paid in connection with the execution and delivery of this Agreement or the sale, issuance and delivery of the Shares by the Company through the facilities of the Depositary Trust Company (“DTC”). The existing composition agreement relating to the Ordinary Shares dated September 15, 2014 between the Company and the Irish Revenue Commissioners (as amended, modified or supplemented from time to time) (the “Composition Agreement”) and the existing special eligibility agreement for securities relating to shares in the Company dated September 19, 2014 between, among others, the Company, DTC, Cede & Co. and the National Securities Clearing Corporation (as amended, modified or supplemented from time to time) (the “SEAS”) apply to the Shares on the Closing Date and any Shares issued at any time after the Closing Date will be subject to the Composition Agreement and the SEAS at their time of issue.

(rr) Testing-the-Waters Materials. The Company has (i) not alone engaged in any Testing-the-Waters Communications other than Testing-the-Waters Communications with the consent of the Representatives with entities that are qualified institutional buyers within the meaning of Rule 144A under the Securities Act or institutions that are accredited investors within the meaning of Rule 501 under the Securities Act and (ii) not authorized anyone to engage in Testing-the-Waters Communications. The Company has not distributed any Testing-the-Waters Communication that is a written communication within the meaning of Rule 405 under the Securities Act. “Testing-the-Waters Communication” means any oral or written communication with potential investors undertaken in reliance on either Section 5(d) of, or Rule 163B under, the Securities Act.

Any certificate contemplated hereby and signed by any officer of the Company or any of its subsidiaries and delivered to the Representatives or to counsel for the

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Underwriters shall be deemed a representation and warranty by the Company to each Underwriter as to the matters covered thereby.

The Company acknowledges that the Underwriters and, for purposes of the opinions to be delivered pursuant to Section 5 hereof, counsel to the Company and counsel to the Underwriters, will rely upon the accuracy and truthfulness of the foregoing representations and hereby consents to such reliance.

2. Agreements to Sell and Purchase. The Company hereby agrees to sell to the several Underwriters, and each Underwriter, upon the basis of the representations and warranties herein contained, but subject to the conditions hereinafter stated, agrees, severally and not jointly, to purchase from the Company at $67.9825 a share (the “Purchase Price”) the number of Firm Shares (subject to such adjustments to eliminate fractional shares as you may determine) that bears the same proportion to the number of Firm Shares to be sold by the Company as the number of Firm Shares set forth in Schedule I hereto opposite the name of such Underwriter bears to the total number of Firm Shares.

On the basis of the representations and warranties contained in this Agreement, and subject to its terms and conditions, the Company agrees to sell to the Underwriters the Additional Shares, and the Underwriters shall have the right to purchase, severally and not jointly, up to the number of Additional Shares set forth in Schedule II hereto at the Purchase Price, provided, however, that the amount paid by the Underwriters for any Additional Shares shall be reduced by an amount per share equal to any dividends declared by the Company and payable on the Firm Shares but not payable on such Additional Shares. You may exercise this right on behalf of the Underwriters in whole or from time to time in part by giving written notice not later than 30 days after the date of this Agreement. Any exercise notice shall specify the number of Additional Shares to be purchased by the Underwriters and the date on which such shares are to be purchased. Each purchase date must be at least one business day after the written notice is given and may not be earlier than the closing date for the Firm Shares nor later than ten business days after the date of such notice. Additional Shares may be purchased as provided in Section 4 hereof solely for the purpose of covering sales of shares in excess of the number of Firm Shares. On each day, if any, that Additional Shares are to be purchased (an “Option Closing Date”), each Underwriter agrees, severally and not jointly, to purchase the number of Additional Shares (subject to such adjustments to eliminate fractional shares as you may determine) that bears the same proportion to the total number of Additional Shares to be purchased on such Option Closing Date as the number of Firm Shares set forth in Schedule I hereto opposite the name of such Underwriter bears to the total number of Firm Shares.

3. Public Offering. The Company is advised by you that the Underwriters propose to make a public offering of their respective portions of the Shares as soon after the Registration Statement and this Agreement have become effective as in your judgment is advisable. The Company is further advised by you that the Shares are to be offered to the public upon the terms set forth in the Prospectus.

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4. Payment and Delivery. Payment for the Firm Shares shall be made to the Company in Federal or other funds immediately available in New York City on the closing date and time set forth in Schedule II hereto, or at such other time on the same or such other date, not later than the fifth business day thereafter, as may be designated in writing by you. The time and date of such payment are hereinafter referred to as the “Closing Date.”

Payment for any Additional Shares shall be made to the Company in Federal or other funds immediately available in New York City on the date specified in the corresponding notice described in Section 2 or at such other time on the same or on such other date, in any event not later than the tenth business day thereafter, as may be designated in writing by you.

The Company agrees that the Firm Shares and the Additional Shares shall be registered in such names and in such denominations as you shall request in writing not later than one full business day prior to the Closing Date or the applicable Option Closing Date, as the case may be, for the respective accounts of the several Underwriters, with any transfer taxes payable in connection with the transfer of the Shares to the Underwriters duly paid, against payment of the Purchase Price therefor. Delivery of the Firm Shares shall be made through the facilities of DTC. The certificates for the Shares, if any, will be made available for inspection and packaging by the Underwriters at the office of DTC or its designated custodian not later than 1:00 P.M., New York City time, on the Closing Date or in the case of Additional Shares on the date of issue of such Additional Shares.

5. Conditions to the Underwriters’ Obligations. The several obligations of the Underwriters are subject to the following conditions:

(a) Subsequent to the execution and delivery of this Agreement and prior to the Closing Date:

(i) no order suspending the effectiveness of the Registration Statement shall be in effect, and no proceeding for such purpose or pursuant to Section 8A under the Securities Act shall be pending before or threatened by the Commission;

(ii) there shall not have occurred any downgrading, nor shall any notice have been given of any intended or potential downgrading or of any review for a possible change that does not indicate the direction of the possible change, in the rating accorded any of the securities of the Company or any of its subsidiaries by any “nationally recognized statistical rating organization,” as such term is defined in Section 3(a)(62) of the Exchange Act; and

(iii) there shall not have occurred any change, or any development involving a prospective change, in the condition, financial or otherwise, or in the earnings, business or operations of the Company and its subsidiaries, taken as a whole, from that set forth in the Time of Sale Prospectus that, in your judgment, is

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material and adverse and that makes it, in your judgment, impracticable to market the Shares on the terms and in the manner contemplated in the Time of Sale Prospectus.

(b) The Representatives shall have received on the Closing Date a certificate, dated the Closing Date and signed by an executive officer of the Company, to the effect set forth in Section 5(a)(i) above and to the effect that the representations and warranties of the Company contained in this Agreement are true and correct as of the Closing Date and that the Company has complied with all of the agreements and satisfied all of the conditions on its part to be performed or satisfied hereunder on or before the Closing Date.

(c) The Representatives shall have received on the Closing Date an opinion and negative assurance letter of Cooley LLP, outside counsel for the Company, dated the Closing Date, in form and substance satisfactory to the Representatives.

(d) The Representatives shall have received on the Closing Date an opinion of Matheson, Irish counsel for the Company, dated the Closing Date, in form and substance satisfactory to the Representatives.

(e) The Representatives shall have received on the Closing Date an opinion and negative assurance letter of Davis Polk & Wardwell LLP, counsel for the Underwriters, dated the Closing Date, in form and substance satisfactory to the Representatives.

The opinion of counsel for the Company described in Section 5(c) and (d) above shall be rendered to the Representatives at the request of the Company and may so state therein.

(f) The Underwriters shall have received, on each of the date hereof and the Closing Date, a letter dated the date hereof or the Closing Date, as the case may be, in form and substance satisfactory to the Representatives, from PricewaterhouseCoopers LLP, independent public accountants, containing statements and information of the type ordinarily included in accountants’ “comfort letters” to underwriters with respect to the financial statements and certain financial information contained or incorporated by reference in the Registration Statement, the Time of Sale Prospectus and the Prospectus.

(g) The “lock-up” agreements, each substantially in the form of Exhibit A hereto, between you and the persons listed on Exhibit B hereto relating to sales and certain other dispositions of Ordinary Shares or certain other securities, delivered to you on or before the date hereof, shall be in full force and effect on the Closing Date.

(h) The Underwriters shall have received, on each of the date hereof and the Closing Date, a certificate (each, a “CFO Certificate”), in form and substance reasonably satisfactory to the Representatives.

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(i) The several obligations of the Underwriters to purchase Additional Shares hereunder are subject to the delivery to you on the applicable Option Closing Date of the following:

(i) a certificate, dated the Option Closing Date and signed by an executive officer of the Company, confirming that the certificate delivered on the Closing Date pursuant to Section 5(b) hereof remains true and correct as of such Option Closing Date;

(ii) an opinion and negative assurance letter of Cooley LLP, outside counsel for the Company, dated the Option Closing Date, relating to the Additional Shares to be purchased on such Option Closing Date and otherwise to the same effect as the opinion required by Section 5(c) hereof;

(iii) an opinion of Matheson, Irish counsel for the Company, dated the Option Closing Date, relating to the Additional Shares to be purchased on such Option Closing Date and otherwise to the same effect as the opinion required by Section 5(d) hereof;

(iv) an opinion and negative assurance letter of Davis Polk & Wardwell LLP, counsel for the Underwriters, dated the Option Closing Date, relating to the Additional Shares to be purchased on such Option Closing Date and otherwise to the same effect as the opinion required by Section 5(e) hereof;

(v) a letter dated the Option Closing Date, in form and substance satisfactory to the Representatives, from PricewaterhouseCoopers LLP, independent public accountants, substantially in the same form and substance as the letter furnished to the Underwriters pursuant to Section 5(f) hereof; provided that the letter delivered on the Option Closing Date from PricewaterhouseCoopers LLP shall use a “cut-off date” not earlier than three business days prior to such Option Closing Date;

(vi) a CFO certificate dated the Option Closing Date, in form and substance satisfactory to the Representatives, substantially in the same form and substance as the letter furnished to the Underwriters pursuant to Section 5(h) hereof; and

(vii) such other documents as you may reasonably request with respect to the good standing of the Company, the due authorization and issuance of the Additional Shares to be sold on such Option Closing Date and other matters related to the issuance of such Additional Shares.

6. Covenants of the Company. The Company covenants with each Underwriter as follows:

(a) To furnish to you, without charge, a signed copy of the Registration Statement (including exhibits thereto and documents incorporated by reference therein)

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and to deliver to each of the Underwriters during the period mentioned in Section 6(e) or 6(f) below, as many copies of the Time of Sale Prospectus, the Prospectus, any documents incorporated by reference therein and any supplements and amendments thereto or to the Registration Statement as you may reasonably request.

(b) Before amending or supplementing the Registration Statement, the Time of Sale Prospectus or the Prospectus, to furnish to you a copy of each such proposed amendment or supplement and not to file any such proposed amendment or supplement to which you reasonably object and to file with the Commission within the applicable period specified in Rule 424(b) under the Securities Act any prospectus required to be filed pursuant to such Rule.

(c) To furnish to you a copy of each proposed free writing prospectus to be prepared by or on behalf of, used by, or referred to by the Company and not to use or refer to any such proposed free writing prospectus to which you reasonably object.

(d) Not to take any action that would result in an Underwriter or the Company being required to file with the Commission pursuant to Rule 433(d) under the Securities Act a free writing prospectus prepared by or on behalf of the Underwriter that the Underwriter otherwise would not have been required to file thereunder.

(e) If the Time of Sale Prospectus is being used to solicit offers to buy the Shares at a time when the Prospectus is not yet available to prospective purchasers and any event shall occur or condition exist as a result of which it is necessary to amend or supplement the Time of Sale Prospectus in order to make the statements therein, in the light of the circumstances, not misleading, or if any event shall occur or condition exist as a result of which the Time of Sale Prospectus conflicts with the information contained in the Registration Statement then on file, or if, in the opinion of counsel for the Underwriters, it is necessary to amend or supplement the Time of Sale Prospectus to comply with applicable law, forthwith to prepare, file with the Commission and furnish, at its own expense, to the Underwriters and to any dealer upon request, either amendments or supplements to the Time of Sale Prospectus so that the statements in the Time of Sale Prospectus as so amended or supplemented will not, in the light of the circumstances when the Time of Sale Prospectus is delivered to a prospective purchaser, be misleading or so that the Time of Sale Prospectus, as amended or supplemented, will no longer conflict with the Registration Statement, or so that the Time of Sale Prospectus, as amended or supplemented, will comply with applicable law.

(f) If, during such period after the first date of the public offering of the Shares as in the opinion of counsel for the Underwriters the Prospectus (or in lieu thereof the notice referred to in Rule 173(a) of the Securities Act) is required by law to be delivered in connection with sales by an Underwriter or dealer, any event shall occur or condition exist as a result of which it is necessary to amend or supplement the Prospectus in order to make the statements therein, in the light of the circumstances when the Prospectus (or in lieu thereof the notice referred to in Rule 173(a) of the Securities Act) is delivered to a purchaser, not misleading, or if, in the opinion of counsel for the Underwriters, it is necessary to amend or supplement the Prospectus to comply with applicable law,

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forthwith to prepare, file with the Commission and furnish, at its own expense, to the Underwriters and to the dealers (whose names and addresses you will furnish to the Company) to which Shares may have been sold by you on behalf of the Underwriters and to any other dealers upon request, either amendments or supplements to the Prospectus so that the statements in the Prospectus as so amended or supplemented will not, in the light of the circumstances when the Prospectus (or in lieu thereof the notice referred to in Rule 173(a) of the Securities Act) is delivered to a purchaser, be misleading or so that the Prospectus, as amended or supplemented, will comply with applicable law.

(g) To endeavor to qualify the Shares for offer and sale under the securities or Blue Sky laws of such jurisdictions as you shall reasonably request.

(h) To make generally available to the Company’s security holders and to you as soon as practicable an earnings statement covering a period of at least twelve months beginning with the first fiscal quarter of the Company occurring after the date of this Agreement which shall satisfy the provisions of Section 11(a) of the Securities Act and the rules and regulations of the Commission thereunder.

(i) Whether or not the transactions contemplated in this Agreement are consummated or this Agreement is terminated, to pay or cause to be paid all expenses incident to the performance of its obligations under this Agreement, including: (i) the fees, disbursements and expenses of the Company’s counsel and the Company’s accountants in connection with the registration and delivery of the Shares under the Securities Act and all other fees or expenses in connection with the preparation and filing of the Registration Statement, any preliminary prospectus, the Time of Sale Prospectus, the Prospectus, any free writing prospectus prepared by or on behalf of, used by, or referred to by the Company and amendments and supplements to any of the foregoing, including the filing fees payable to the Commission relating to the Shares (within the time required by Rule 456(b)(1), if applicable), all printing costs associated therewith, and the mailing and delivering of copies thereof to the Underwriters and dealers, in the quantities hereinabove specified, (ii) all costs and expenses of the Company’s transfer agent related to the transfer and delivery of the Shares to the Underwriters, (iii) the cost of printing or producing any Blue Sky or Legal Investment memorandum in connection with the offer and sale of the Shares under state securities laws and all expenses in connection with the qualification of the Shares for offer and sale under state securities laws as provided in Section 6(g) hereof, including filing fees and the reasonable fees and disbursements of counsel for the Underwriters in connection with such qualification and in connection with the Blue Sky or Legal Investment memorandum (provided that such counsel fees shall not exceed $5,000), (iv) all filing fees and the reasonable fees and disbursements of counsel to the Underwriters incurred in connection with the review and qualification of the offering of the Shares by the Financial Industry Regulatory Authority (provided that such counsel fees shall not exceed $5,000), (v) all costs and expenses incident to listing the Shares on the Nasdaq Global Select Market, (vi) the cost of printing certificates representing the Shares, (vii) the costs and charges of any transfer agent, registrar or depositary, (viii) the costs and expenses of the Company relating to investor presentations on any “road show” undertaken in connection with the marketing of the offering of the Shares, including, without limitation, expenses associated with the

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preparation or dissemination of any electronic road show, expenses associated with the production of road show slides and graphics, fees and expenses of any consultants engaged in connection with the road show presentations with the prior approval of the Company, travel and lodging expenses of the representatives and officers of the Company and any such consultants, and 50% of the cost of any aircraft chartered in connection with the road show, (ix) the document production charges and expenses associated with printing this Agreement, and (x) all other costs and expenses incident to the performance of the obligations of the Company hereunder for which provision is not otherwise made in this Section. It is understood, however, that except as provided in this Section, Section 8 entitled “Indemnity and Contribution” and the last paragraph of Section 10 below, the Underwriters will pay all of their costs and expenses, including fees and disbursements of their counsel, stock transfer taxes payable on resale of any of the Shares by them and any advertising expenses connected with any offers they may make.

(j) All payments by the Company to an Underwriter under this Agreement shall be made without withholding or deduction of any present or future Irish taxes, duties or governmental charges of any kind, unless that withholding or deduction is required by law. If the Company is required to deduct or withhold from a payment to an Underwriter any such tax, duty or governmental charge, or if such tax, duty or governmental charge is required to be paid by an Underwriter in connection with this Agreement (excluding any tax imposed on or calculated by reference to the net income or capital gains earned, accrued or realized by such Underwriter or franchise taxes imposed on such Underwriter by Ireland as a result of any present or former connection (other than any connection resulting solely from the transactions contemplated by this Agreement) between such Underwriter and Ireland), the Company agrees to pay to the relevant Underwriter such additional amounts as shall be required so that the net amount received by such Underwriter after such deduction, withholding or payment shall equal the amount that would have been received by such Underwriter had no such deduction, withholding or payment been made.

(k) If requested by the Representatives, to prepare a final term sheet relating to the offering of the Shares, containing only information that describes the final terms of the offering in a form consented to by the Representatives, and to file such final term sheet within the period required by Rule 433(d)(5)(ii) under the Securities Act following the date the final terms have been established for the offering of the Shares.

(l) The Company also covenants with each Underwriter that, without the prior written consent of Citigroup Global Markets Inc., Morgan Stanley & Co. LLC, and J.P. Morgan Securities LLC, on behalf of the Underwriters with the authorization to release this lock-up on behalf of the Underwriters, it will not, and will not publicly disclose an intention to, during the restricted period set forth in Schedule II hereto (the “Restricted Period”), (1) offer, pledge, sell, contract to sell, sell any option or contract to purchase, purchase any option or contract to sell, grant any option, right or warrant to purchase, lend, or otherwise transfer or dispose of, directly or indirectly, any Ordinary Shares or any securities convertible into or exercisable or exchangeable for Ordinary Shares or (2) enter into any swap or other arrangement that transfers to another, in whole or in part, any of the economic consequences of ownership of the Ordinary Shares, whether any such

24

transaction described in clause (1) or (2) above is to be settled by delivery of Ordinary Shares or such other securities, in cash or otherwise or (3) file any registration statement with the Commission relating to the offering of Ordinary Shares or any securities convertible into or exercisable or exchangeable for Ordinary Shares. The foregoing sentence shall not apply to (a) the Shares to be sold hereunder, (b) the issuance by the Company of Ordinary Shares upon the exercise of an option or warrant, settlement of any restricted stock unit or the conversion of a security outstanding on the date hereof and described in the Time of Sale Prospectus or of which the Underwriters have been advised in writing, (c) the establishment of a trading plan pursuant to Rule 10b5-1 under the Exchange Act for the transfer of Ordinary Shares, provided that (i) such plan does not provide for the transfer of Ordinary Shares during the Restricted Period and (ii) to the extent a public announcement or filing under the Exchange Act, if any, is required of or voluntarily made by the Company regarding the establishment of such plan, such announcement or filing shall include a statement to the effect that no transfer of Ordinary Shares may be made under such plan during the Restricted Period, (d) the issuance by the Company of Ordinary Shares or other securities convertible into or exercisable for, or that represent the right to receive, Ordinary Shares pursuant to the Company’s equity incentive plans described in the Time of Sale Prospectus, (e) the entry into an agreement by the Company providing for the issuance by the Company of Ordinary Shares or any security convertible into or exercisable for Ordinary Shares in connection with the acquisition by the Company or any of its subsidiaries of the securities, business, or other assets of another person or entity or pursuant to an employee benefit plan assumed by the Company in connection with such acquisition, and the issuance of any such securities pursuant to any such agreement, (f) the entry into an agreement by the Company providing for the issuance of Ordinary Shares or any security convertible into or exercisable for Ordinary Shares in connection with joint ventures, commercial relationships or other strategic transactions, and the issuance of any such securities pursuant to any such agreement; provided that in the case of clauses (e) and (f), the aggregate number of Ordinary Shares that the Company may sell or issue or agree to sell or issue, or that may be issuable upon conversion or exercise of all other securities that the Company may sell or issue or agree to sell or issue, pursuant to clauses (e) and (f) shall not exceed 5% of the total number of Ordinary Shares issued and outstanding on the date hereof; and provided further, that each recipient of shares or other securities issued pursuant to clause (e) or (f) shall execute a lock-up agreement substantially in the form of Exhibit A hereto, or (g) the filing of any registration statements (i) on Form S-8, (ii) in connection with the transactions contemplated by clauses (e) and (f), or (iii) required by the terms of existing registration rights agreements described in the Time of Sale Prospectus.

7. Covenants of the Underwriters. Each Underwriter, severally and not jointly, covenants with the Company not to take any action that would result in the Company being required to file with the Commission under Rule 433(d) a free writing prospectus prepared by or on behalf of such Underwriter that otherwise would not be required to be filed by the Company thereunder, but for the action of the Underwriter.

8. Indemnity and Contribution. (a) The Company agrees to indemnify and hold harmless or cause to indemnify and hold harmless each Underwriter, the directors,

25

officers, employees, affiliates and agents of each Underwriter and each person who controls any Underwriter within the meaning of either the Act or the Exchange Act from and against any and all losses, claims, damages and liabilities (including, without limitation, any legal or other expenses reasonably incurred in connection with defending or investigating any such action or claim) caused by any untrue statement or alleged untrue statement of a material fact contained in the Registration Statement or any amendment thereof, any preliminary prospectus, the Time of Sale Prospectus or any amendment or supplement thereto, any issuer free writing prospectus as defined in Rule 433(h) under the Securities Act, any Company information that the Company has filed, or is required to file, pursuant to Rule 433(d) under the Securities Act, any “road show” as defined in Rule 433(h) under the Securities Act (a “road show”), the Prospectus or any amendment or supplement thereto, or any Testing-the-Waters Communication, or caused by any omission or alleged omission to state therein a material fact required to be stated therein or necessary to make the statements therein not misleading, except insofar as such losses, claims, damages or liabilities are caused by any such untrue statement or omission or alleged untrue statement or omission based upon information relating to any Underwriter furnished to the Company in writing by such Underwriter through you expressly for use therein.

(b) Each Underwriter agrees, severally and not jointly, to indemnify and hold harmless the Company, the directors of the Company, the officers of the Company who sign the Registration Statement and each person, if any, who controls the Company within the meaning of either Section 15 of the Securities Act or Section 20 of the Exchange Act from and against any and all losses, claims, damages and liabilities (including, without limitation, any legal or other expenses reasonably incurred in connection with defending or investigating any such action or claim) caused by any untrue statement or alleged untrue statement of a material fact contained in the Registration Statement or any amendment thereof, any preliminary prospectus, the Time of Sale Prospectus or any amendment or supplement thereto, any issuer free writing prospectus as defined in Rule 433(h) under the Securities Act, any Company information that the Company has filed, or is required to file, pursuant to Rule 433(d) under the Securities Act, any road show, or the Prospectus or any amendment or supplement thereto, or caused by any omission or alleged omission to state therein a material fact required to be stated therein or necessary to make the statements therein not misleading, but only with reference to information relating to such Underwriter furnished to the Company in writing by such Underwriter through you expressly for use in the Registration Statement, any preliminary prospectus, the Time of Sale Prospectus, any issuer free writing prospectus, road show or the Prospectus or any amendment or supplement thereto; it being agreed and understood that they only such information furnished by any Underwriter consists of the following information in the Prospectus furnished on behalf of each Underwriter under the heading “Underwriting”: the third paragraph beginning with the words “The underwriters have advised us”, the last sentence of the fourth paragraph beginning with the words “Any ordinary shares issued or sold”, the twelfth paragraph beginning with the words “In connection with this offering”, the thirteenth paragraph beginning with the words “Purchases to cover short

26

positions” and the fourteenth paragraph beginning with the words “In addition, in connection with this offering”.

(c) In case any proceeding (including any governmental investigation) shall be instituted involving any person in respect of which indemnity may be sought pursuant to Section 8(a) or 8(b) such person (the “indemnified party”) shall promptly notify the person against whom such indemnity may be sought (the “indemnifying party”) in writing and the indemnifying party, upon request of the indemnified party, shall retain counsel reasonably satisfactory to the indemnified party to represent the indemnified party and any others the indemnifying party may designate in such proceeding and shall pay reasonably incurred fees and disbursements of such counsel related to such proceeding. In any such proceeding, any indemnified party shall have the right to retain its own counsel, but the fees and expenses of such counsel shall be at the expense of such indemnified party unless (i) the indemnifying party and the indemnified party shall have mutually agreed to the retention of such counsel or (ii) the named parties to any such proceeding (including any impleaded parties) include both the indemnifying party and the indemnified party and representation of both parties by the same counsel would be inappropriate due to actual or potential differing interests between them. It is understood that the indemnifying party shall not, in respect of the legal expenses of any indemnified party in connection with any proceeding or related proceedings in the same jurisdiction, be liable for (i) the fees and expenses of more than one separate firm (in addition to any local counsel) for all Underwriters and all persons, if any, who control any Underwriter within the meaning of either Section 15 of the Securities Act or Section 20 of the Exchange Act or who are affiliates of any Underwriter within the meaning of Rule 405 under the Securities Act and (ii) the fees and expenses of more than one separate firm (in addition to any local counsel) for the Company, its directors, its officers who sign the Registration Statement and each person, if any, who controls the Company within the meaning of either such Section, and that all such fees and expenses shall be reimbursed as they are incurred. In the case of any such separate firm for the Underwriters and such control persons and affiliates of any Underwriters, such firm shall be designated in writing by the Representatives. In the case of any such separate firm for the Company, and such directors, officers and control persons of the Company, such firm shall be designated in writing by the Company. The indemnifying party shall not be liable for any settlement of any proceeding effected without its written consent, but if settled with such consent or if there be a final judgment for the plaintiff, the indemnifying party agrees to indemnify the indemnified party from and against any loss or liability by reason of such settlement or judgment. Notwithstanding the foregoing sentence, if at any time an indemnified party shall have requested an indemnifying party to reimburse the indemnified party for fees and expenses of counsel as contemplated by the second and third sentences of this paragraph, the indemnifying party agrees that it shall be liable for any settlement of any proceeding effected without its written consent if (i) such settlement is entered into more than 60 days after receipt by such indemnifying party of the aforesaid request and (ii) such indemnifying party shall not have reimbursed the indemnified party in accordance with such request prior to the date of such settlement. No indemnifying party shall, without the prior written consent of the indemnified party, effect any settlement of any pending or threatened proceeding in respect of which any

27

indemnified party is or could have been a party and indemnity could have been sought hereunder by such indemnified party, unless such settlement (i) includes an unconditional release of such indemnified party from all liability on claims that are the subject matter of such proceeding and (ii) does not include an admission of fault.

(d) To the extent the indemnification provided for in Section 8(a) or 8(b) is unavailable to an indemnified party or insufficient in respect of any losses, claims, damages or liabilities referred to therein, then each indemnifying party under such paragraph, in lieu of indemnifying such indemnified party thereunder, shall contribute or cause to be contributed to the amount paid or payable by such indemnified party as a result of such losses, claims, damages or liabilities (i) in such proportion as is appropriate to reflect the relative benefits received by the indemnifying party or parties on the one hand and the indemnified party or parties on the other hand from the offering of the Shares or (ii) if the allocation provided by clause 8(d)(i) above is not permitted by applicable law, in such proportion as is appropriate to reflect not only the relative benefits referred to in clause 8(d)(i) above but also the relative fault of the indemnifying party or parties on the one hand and of the indemnified party or parties on the other hand in connection with the statements or omissions that resulted in such losses, claims, damages or liabilities, as well as any other relevant equitable considerations. The relative benefits received by the Company and the Underwriters in connection with the offering of the Shares shall be deemed to be in the same respective proportions as the net proceeds from the offering of the Shares (before deducting expenses) received by the Company and the total underwriting discounts and commissions received by each Underwriter, in each case as set forth in the table on the cover of the Prospectus, bear to the aggregate offering price of the Shares. The relative fault of the Company and the Underwriters shall be determined by reference to, among other things, whether the untrue or alleged untrue statement of a material fact or the omission or alleged omission to state a material fact relates to information supplied by the Company or by the Underwriters and the parties’ relative intent, knowledge, access to information and opportunity to correct or prevent such statement or omission. The Underwriters’ respective obligations to contribute pursuant to this Section 8 are several in proportion to the respective number of Shares they have purchased or sold hereunder, as the case may be, and not joint.

(e) The Company and the Underwriters agree that it would not be just or equitable if contribution pursuant to this Section 8 were determined by pro rata allocation (even if the Underwriters were treated as one entity for such purpose) or by any other method of allocation that does not take account of the equitable considerations referred to in Section 8(d). The amount paid or payable by an indemnified party as a result of the losses, claims, damages and liabilities referred to in Section 8(d) shall be deemed to include, subject to the limitations set forth above, any legal or other expenses reasonably incurred by such indemnified party in connection with investigating or defending any such action or claim. Notwithstanding the provisions of this Section 8, no Underwriter shall be required to contribute any amount in excess of the total underwriting discounts and commissions less the amount of any damages that such Underwriter has otherwise been required to pay by reason of such untrue or alleged untrue statement or omission or alleged omission. No person guilty of fraudulent misrepresentation (within the meaning of Section 11(f) of the Securities Act) shall be entitled to contribution from

28

any person who was not guilty of such fraudulent misrepresentation. The remedies provided for in this Section 8 are not exclusive and shall not limit any rights or remedies which may otherwise be available to any indemnified party at law or in equity.

(f) The indemnity and contribution provisions contained in this Section 8 and the representations, warranties and other statements of the Company contained in this Agreement shall remain operative and in full force and effect regardless of (i) any termination of this Agreement, (ii) any investigation made by or on behalf of any Underwriter, any person controlling any Underwriter or any affiliate of any Underwriter, or the Company, its officers or directors or any person controlling the Company and (iii) acceptance of and payment for any of the Shares.

9. Termination. The Underwriters may terminate this Agreement by notice given by you to the Company, if after the execution and delivery of this Agreement and prior to the Closing Date or any Option Closing Date, as the case may be, (i) trading generally shall have been suspended or materially limited on, or by, as the case may be, any of the New York Stock Exchange, the NYSE MKT, the Nasdaq Global Select Market, the Chicago Board of Options Exchange, the Chicago Mercantile Exchange or the Chicago Board of Trade, (ii) trading of any securities of the Company shall have been suspended on any exchange or in any over-the-counter market, (iii) a material disruption in securities settlement, payment or clearance services in the United States shall have occurred, (iv) any moratorium on commercial banking activities shall have been declared by Federal or New York State authorities or (v) there shall have occurred any outbreak or escalation of hostilities, or any change in financial markets or any calamity or crisis that, in your judgment, is material and adverse and which, singly or together with any other event specified in this clause (v), makes it, in your judgment, impracticable or inadvisable to proceed with the offer, sale or delivery of the Shares on the terms and in the manner contemplated in the Time of Sale Prospectus or the Prospectus.

10. Effectiveness; Defaulting Underwriters. This Agreement shall become effective upon the execution and delivery hereof by the parties hereto.

If, on the Closing Date or an Option Closing Date, as the case may be, any one or more of the Underwriters shall fail or refuse to purchase Shares that it has or they have agreed to purchase hereunder on such date, and the aggregate number of Shares which such defaulting Underwriter or Underwriters agreed but failed or refused to purchase is not more than one-tenth of the aggregate number of the Shares to be purchased on such date, the other Underwriters shall be obligated severally in the proportions that the number of Firm Shares set forth opposite their respective names in Schedule I bears to the aggregate number of Firm Shares set forth opposite the names of all such non-defaulting Underwriters, or in such other proportions as you may specify, to purchase the Shares which such defaulting Underwriter or Underwriters agreed but failed or refused to purchase on such date; provided that in no event shall the number of Shares that any Underwriter has agreed to purchase pursuant to this Agreement be increased pursuant to this Section 10 by an amount in excess of one-ninth of such number of Shares without the written consent of such Underwriter. If, on the Closing Date, any Underwriter or Underwriters shall fail or refuse to purchase Firm Shares and the aggregate number of

29

Firm Shares with respect to which such default occurs is more than one-tenth of the aggregate number of Firm Shares to be purchased on such date, and arrangements satisfactory to you and the Company for the purchase of such Firm Shares are not made within 36 hours after such default, this Agreement shall terminate without liability on the part of any non-defaulting Underwriter or the Company. In any such case either you or the Company shall have the right to postpone the Closing Date, but in no event for longer than seven days, in order that the required changes, if any, in the Registration Statement, in the Time of Sale Prospectus, in the Prospectus or in any other documents or arrangements may be effected. If, on an Option Closing Date, any Underwriter or Underwriters shall fail or refuse to purchase Additional Shares and the aggregate number of Additional Shares with respect to which such default occurs is more than one-tenth of the aggregate number of Additional Shares to be purchased on such Option Closing Date, the non-defaulting Underwriters shall have the option to (i) terminate their obligation hereunder to purchase the Additional Shares to be sold on such Option Closing Date or (ii) purchase not less than the number of Additional Shares that such non-defaulting Underwriters would have been obligated to purchase in the absence of such default. Any action taken under this paragraph shall not relieve any defaulting Underwriter from liability in respect of any default of such Underwriter under this Agreement.

If this Agreement shall be terminated by the Underwriters, or any of them, because of any failure or refusal on the part of the Company to comply with the terms or to fulfill any of the conditions of this Agreement, or if for any reason the Company shall be unable to perform its obligations under this Agreement, the Company will reimburse the Underwriters or such Underwriters as have so terminated this Agreement with respect to themselves, severally, for all out-of-pocket expenses (including the fees and disbursements of their counsel) reasonably incurred by such Underwriters in connection with this Agreement or the offering contemplated hereunder; provided, however, that in the event any such termination is effected after the Closing Date but prior to any Option Closing Date with respect to the purchase of any Additional Shares, the Company shall only reimburse the Underwriters for all of their out-of-pocket expenses, including the reasonable fees and disbursements of counsel for the Underwriters, incurred after the Closing Date in connection with the proposed purchase of any such Additional Shares.

11. Waiver of Jury Trial. The Company and each Underwriter hereby irrevocably waives, to the fullest extent permitted by applicable law, any and all right to trial by jury in any legal proceeding arising out of or relating to this Agreement or the transactions contemplated hereby.

12. Recognition of the U.S. Special Resolution Regimes.

(a) In the event that any Underwriter that is a Covered Entity becomes subject to a proceeding under a U.S. Special Resolution Regime, the transfer from such Underwriter of this Agreement, and any interest and obligation in or under this Agreement, will be effective to the same extent as the transfer would be effective under the U.S. Special Resolution Regime if this Agreement, and any such interest and obligation, were governed by the laws of the United States or a state of the United States.

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(b) In the event that any Underwriter that is a Covered Entity or a BHC Act Affiliate of such Underwriter becomes subject to a proceeding under a U.S. Special Resolution Regime, Default Rights under this Agreement that may be exercised against such Underwriter are permitted to be exercised to no greater extent than such Default Rights could be exercised under the U.S. Special Resolution Regime if this Agreement were governed by the laws of the United States or a state of the United States.

As used in this Section 12, “BHC Act Affiliate” has the meaning assigned to the term “affiliate” in, and shall be interpreted in accordance with, 12 U.S.C. § 1841(k); “Covered Entity” means any of the following: (i) a “covered entity” as that term is defined in, and interpreted in accordance with, 12 C.F.R. § 252.82(b), (ii) a “covered bank” as that term is defined in, and interpreted in accordance with, 12 C.F.R. § 47.3(b) or (iii) a “covered FSI” as that term is defined in, and interpreted in accordance with, 12 C.F.R. § 382.2(b); “Default Right” has the meaning assigned to that term in, and shall be interpreted in accordance with, 12 C.F.R. §§ 252.81, 47.2 or 382.1, as applicable; and “U.S. Special Resolution Regime” means each of (i) the Federal Deposit Insurance Act and the regulations promulgated thereunder and (ii) Title II of the Dodd-Frank Wall Street Reform and Consumer Protection Act and the regulations promulgated thereunder

13. Entire Agreement. (a) This Agreement, together with any contemporaneous written agreements and any prior written agreements (to the extent not superseded by this Agreement) that relate to the offering of the Shares, represents the entire agreement between the Company, on the one hand, and the Underwriters, on the other, with respect to the preparation of any preliminary prospectus, the Time of Sale Prospectus, the Prospectus, the conduct of the offering, and the purchase and sale of the Shares.

(b) The Company acknowledges that in connection with the offering of the Shares: (i) the Underwriters have acted at arm’s length, are not agents of, and owe no fiduciary duties to, the Company or any other person, (ii) the Underwriters owe the Company only those duties and obligations set forth in this Agreement, any contemporaneous written agreements and prior written agreements (to the extent not superseded by this Agreement), if any, (iii) the Underwriters may have interests that differ from those of the Company, and (iv) none of the activities of the Underwriters in connection with the transactions contemplated herein constitutes a recommendation, investment advice, or solicitation of any action by the Underwriters with respect to any entity or natural person. The Company waives to the full extent permitted by applicable law any claims it may have against the Underwriters arising from an alleged breach of fiduciary duty in connection with the offering of the Shares.

14. Counterparts. This Agreement may be signed in two or more counterparts, each of which shall be an original, with the same effect as if the signatures thereto and hereto were upon the same instrument.

15. Applicable Law. This Agreement shall be governed by and construed in accordance with the internal laws of the State of New York.

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(a) Each party irrevocably agrees that any legal suit, action or proceeding arising out of or based upon this Agreement or the transactions contemplated hereby may be instituted in the federal courts of the United States or the courts of the State of New York, in each case located in the Borough of Manhattan in the City of New York (collectively, the “Specified Courts”), and irrevocably submits to the non-exclusive jurisdiction of such courts in any such suit, action or proceeding. The parties hereby irrevocably and unconditionally waive, to the fullest extent permitted by law, any objection to the laying of venue of any lawsuit, action or other proceeding arising out of or relating to this Agreement or the transactions contemplated hereby in the Specified Courts, and hereby further irrevocably and unconditionally waive and agree not to plead or claim in any such court that any such lawsuit, action or other proceeding brought in any such court has been brought in an inconvenient forum. The Company irrevocably appoints Corporation Service Company (the “Authorized Agent”), as its agent to receive service of process or other legal summons for purposes of any such action or proceeding that may be instituted in any state or federal court in the City and State of New York. The Company represents and warrants that the Authorized Agent has agreed to act as agent for service of process and agrees to take any and all action that may be necessary to continue such appointment in full force and effect as aforesaid. Service of process upon the Authorized Agent and written notice of such service to the Company shall be deemed, in every respect, effective service of process upon the Company, as applicable. The foregoing consent to jurisdiction and appointment of the Authorized Agent by the Company shall not: (a) constitute submission to jurisdiction in the State of New York or consent to service of process for any purpose except with respect to any legal suit, action or proceeding arising out of or based upon this Agreement or the transactions contemplated hereby, (b) constitute appointment of the Authorized Agent as agent to receive service of process or other legal summons for any purpose except with respect to any legal suit, action or proceeding arising out of or based upon this Agreement or the transactions contemplated hereby that may be instituted in any state or federal court in the City and State of New York or (c) be deemed to confer rights on any person other than the parties hereto and their respective successors and the officers and directors and any controlling persons referred to in Section 8 hereof.

(b) If for the purposes of obtaining judgment in any court it is necessary to convert a sum due hereunder into any currency other than United States dollars, the parties hereto agree, to the fullest extent permitted by law, that the rate of exchange used shall be the rate at which in accordance with normal banking procedures the Underwriters could purchase United States dollars with such other currency in The City of New York on the business day preceding that on which final judgment is given. The obligation of the Company with respect to any sum due from it to any Underwriter or any person controlling any Underwriter shall, notwithstanding any judgment in a currency other than United States dollars, not be discharged until the first business day following receipt by such Underwriter or controlling person of any sum in such other currency, and only to the extent that such Underwriter or controlling person may in accordance with normal banking procedures purchase United States dollars with such other currency. If the United States dollars so purchased are less than the sum originally due to such Underwriter or controlling person hereunder, the Company agrees as a separate

32

obligation and notwithstanding any such judgment, to indemnify such Underwriter or controlling person against such loss. If the United States dollars so purchased are greater than the sum originally due to such Underwriter or controlling person hereunder, such Underwriter or controlling person agrees to pay to the Company an amount equal to the excess of the dollars so purchased over the sum originally due to such Underwriter or controlling person hereunder.

16. Headings. The headings of the sections of this Agreement have been inserted for convenience of reference only and shall not be deemed a part of this Agreement.

17. Notices. All communications hereunder shall be in writing and effective only upon receipt and if to the Underwriters shall be delivered, mailed or sent to:

Citigroup Global Markets Inc.

388 Greenwich Street

New York, New York 10013

Facsimile: (646) 291-1469

Attention: General Counsel

Morgan Stanley & Co. LLC

1585 Broadway

New York, New York 10036

Attention: Equity Syndicate Desk

with a copy to the Legal Department

J.P. Morgan Securities LLC

383 Madison Avenue

New York, New York 10179

Fax: (212) 622-8358

Attention: Equity Syndicate Desk

Piper Sandler & Co.

800 Nicollet Mall

Minneapolis, Minnesota 55402

Attention: Equity Capital Markets

with a copy to the General Counsel

Stifel, Nicolaus & Company, Incorporated

787 Seventh Avenue, 11th Floor

New York, NY 10019

Attention: Equity Capital Markets

and

if to the Company shall be delivered, mailed or sent to

33

Connaught House, 1st Floor.

1 Burlington Road

Dublin 4, D04 C5Y6

Ireland

[Signature Pages to Follow]

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SCHEDULE I

I-1

SCHEDULE II

II-1

EXHIBIT A

FORM OF LOCK-UP LETTER

August [    ], 2020

Citigroup Global Markets Inc.

Morgan Stanley & Co. LLC

J.P. Morgan Securities LLC

Piper Sandler & Co.

Stifel, Nicolaus & Company, Incorporated

388 Greenwich Street New

York, New York 10013

1585 Broadway

New York, New York 10036

383 Madison Avenue

New York, New York 10179

345 Park Avenue, 12th Floor

New York, New York 10154

787 Seventh Avenue, 11th Floor

New York, New York 10019

Ladies and Gentlemen:

The undersigned understands that Citigroup Global Markets Inc., Morgan Stanley & Co. LLC, J.P. Morgan Securities LLC, Piper Sandler & Co., and Stifel, Nicolaus & Company, Incorporated, as representatives (together, the “Representatives”) of the several Underwriters, including the Representatives (the “Underwriters”), propose to enter into an Underwriting Agreement (the “Underwriting Agreement”) with Horizon Therapeutics Public Limited Company, a public limited company formed under the laws of Ireland (the “Company”), providing for the public offering (the “Public Offering”) by the several Underwriters of a number of ordinary shares (the “Shares”), nominal value $0.0001 per share, of the Company (the “Common Stock”).

To induce the Underwriters that may participate in the Public Offering to continue their efforts in connection with the Public Offering, the undersigned hereby agrees that, without the prior written consent of Citigroup Global Markets Inc., Morgan Stanley &

A-1

Co. LLC, and J.P. Morgan Securities LLC, on behalf of the Underwriters, the undersigned will not, and will not publicly disclose an intention to, during the period commencing on the date hereof and ending 90 days after the date of the final prospectus supplement, (the “Restricted Period”) relating to the Public Offering (the “Prospectus”), (1) offer, pledge, sell, contract to sell, sell any option or contract to purchase, purchase any option or contract to sell, grant any option, right or warrant to purchase, lend, or otherwise transfer or dispose of, directly or indirectly, any shares of Common Stock beneficially owned (as such term is used in Rule 13d-3 of the Securities Exchange Act of 1934, as amended (the “Exchange Act”)), by the undersigned or any other securities so owned convertible into or exercisable or exchangeable for Common Stock or (2) enter into any swap or other arrangement that transfers to another, in whole or in part, any of the economic consequences of ownership of the Common Stock, whether any such transaction described in clause (1) or (2) above is to be settled by delivery of Common Stock or such other securities, in cash or otherwise.

The foregoing paragraph shall not apply to:

(a) transactions relating to shares of Common Stock or other securities of the Company acquired in open market transactions after the completion of the Public Offering, provided that no filing under Section 16(a) of the Exchange Act shall be required or shall be voluntarily made in connection with subsequent sales of Common Stock or other securities of the Company acquired in such open market transactions;

(b) transfers of shares of Common Stock or any security convertible into or exercisable or exchangeable for Common Stock as a bona fide gift or for bona fide estate planning purposes;

(c) distributions of shares of Common Stock or any security convertible into or exercisable or exchangeable for Common Stock to partners, members, managers, stockholders or holders of similar equity interests in the undersigned, or to the estates of any such persons, or to direct or indirect affiliates (within the meaning set forth in Rule 405 under the Securities Act of 1933, as amended) of the undersigned;

(d) transfers of shares of Common Stock or any security convertible into or exercisable or exchangeable for Common Stock by will or intestate succession, or to any trust for the direct or indirect benefit of the undersigned or the immediate family of the undersigned (for purposes of this agreement, “immediate family” shall mean any relationship by blood, current or former marriage or adoption, not more remote than first cousin) or, if the undersigned is a trust, to any beneficiary of the undersigned or the estate of any such beneficiary, provided that in the case of any transfer or distribution pursuant to clause (b), (c) or (d), (i) each donee or distributee shall sign and deliver a lock-up letter substantially in the form of this letter and (ii) no filing under Section 16(a) of the Exchange Act, reporting a reduction in beneficial ownership of shares of Common Stock, shall be required or shall be voluntarily made during the Restricted Period;

(e) any transfers of shares of Common Stock in connection with a “cashless” or “net” exercise of options or warrants to purchase shares of Common Stock or to pay taxes or tax withholding obligations required to be paid or satisfied upon the settlement of

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restricted stock units, provided (i) that any such transfer is to the Company and (ii) any filing under Section 16(a) of the Exchange Act shall clearly indicate in the footnotes thereto (A) that the filing relates to the circumstances described in this clause (e) and (B) that any shares received upon such exercise or settlement are subject to a lock-up agreement with the Underwriters of the Public Offering;

(f) transfers to the Company of shares of Common Stock or other securities convertible into or exercisable or exchangeable for Common Stock in exercise of the Company’s right to repurchase or reacquire the undersigned’s securities pursuant to agreements that permit the Company to repurchase or reacquire such securities upon termination of the undersigned’s services to the Company, provided that any filings under Section 16(a) of the Exchange Act shall state that the transfer is by repurchase by the Company;

(g) the establishment of a trading plan pursuant to Rule 10b5-1 under the Exchange Act for the transfer of shares of Common Stock, provided that (i) such plan does not provide for the transfer of Common Stock during the Restricted Period and (ii) to the extent a public announcement or filing under the Exchange Act, if any, is required of or voluntarily made by or on behalf of the undersigned or the Company regarding the establishment of such plan, such announcement or filing shall include a statement to the effect that no transfer of Common Stock may be made under such plan during the Restricted Period;

(h) transfers or dispositions of shares of Common Stock under a trading plan pursuant to Rule 10b5-1 under the Exchange Act for the transfer or disposition of shares of Common Stock that is existing as of the date hereof; provided that the existence of such plan was communicated to the Representatives and such plan will not be amended or otherwise modified during the Restricted Period; provided further that any filing required by Section 16 of the Exchange Act that is made in connection with any such sales during the Restricted Period shall state that such sales have been executed under a trading plan pursuant to Rule 10b5-1 under the Exchange Act and no other filing or public announcement shall be required or shall be made voluntarily in connection with such sales;

(i) the transfer of shares of Common Stock or any security convertible into or exercisable or exchangeable for Common Stock that occurs by operation of law pursuant to a qualified domestic order in connection with a divorce settlement or other court order, provided that (i) each transferee shall sign and deliver a lock-up letter substantially in the form of this letter and (ii) any filings under Section 16(a) of the Exchange Act shall state that the transfer is by operation of law, court order or in connection with a divorce settlement, as the case may be;

(j) the transfer of shares of Common Stock or any security convertible into or exercisable or exchangeable for Common Stock pursuant to a bona fide third party tender offer, merger, consolidation or other similar transaction that is approved by the Board of Directors of the Company, made to all holders of Common Stock involving a Change of Control (as defined below), provided that in the event that the tender offer, merger,

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consolidation or other such transaction is not completed, the Common Stock owned by the undersigned shall remain subject to the restrictions contained in this agreement; or

(k) sales of Common Stock pursuant to the terms of the Underwriting Agreement.

For the purposes of clause (j), “Change of Control” shall mean the transfer (whether by tender offer, merger, consolidation or other similar transaction), in one transaction or a series of related transactions, to a person or group of affiliated persons (other than an Underwriter pursuant to the Public Offering), of the Company’s voting securities if, after such transfer, such person or group of affiliated persons would hold more than 50% of the outstanding voting securities of the Company (or the surviving entity)

In addition, the undersigned agrees that, without the prior written consent of Citigroup Global Markets Inc., Morgan Stanley & Co. LLC, and J.P. Morgan Securities LLC, on behalf of the Underwriters, it will not, during the Restricted Period, make any demand for or exercise any right with respect to, the registration of any shares of Common Stock or any security convertible into or exercisable or exchangeable for Common Stock. The undersigned also agrees and consents to the entry of stop transfer instructions with the Company’s transfer agent and registrar against the transfer of the undersigned’s shares of Common Stock except in compliance with the foregoing restrictions.

The undersigned understands that the Company and the Underwriters are relying upon this agreement in proceeding toward consummation of the Public Offering. The undersigned further understands that this agreement is irrevocable and shall be binding upon the undersigned’s heirs, legal representatives, successors and assigns.

The undersigned acknowledges and agrees that the Underwriters have not provided any recommendation or investment advice nor have the Underwriters solicited any action from the undersigned with respect to the Public Offering of the Shares and the undersigned has consulted their own legal, accounting, financial, regulatory and tax advisors to the extent deemed appropriate. The undersigned further acknowledges and agrees that, although the Underwriters may provide certain Regulation Best Interest and Form CRS disclosures or other related documentation to the Representatives in connection with the Public Offering, the Underwriters are not making a recommendation to the Representatives to participate in the Public Offering or sell any Shares at the price determined in the Public Offering, and nothing set forth in such disclosures or documentation is intended to suggest that any Underwriter is making such a recommendation.

This agreement shall terminate automatically upon the earlier to occur, if applicable, of (a) the date the Company advises the Representatives, in writing, prior to the execution of the Underwriting Agreement, that it has determined not to proceed with the Public Offering and (b) August 31, 2020 if, and only if, the Underwriting Agreement has not been executed by such date.

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Whether or not the Public Offering actually occurs depends on a number of factors, including market conditions. Any Public Offering will only be made pursuant to an Underwriting Agreement, the terms of which are subject to negotiation between the Company and the Underwriters.

This agreement shall be governed by and construed in accordance with the laws of the State of New York.

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