PROTHENA CORPORATION PLC (an Irish public limited company) 2,767,177 Ordinary Shares UNDERWRITING AGREEMENT

Exhibit 1.1

PROTHENA CORPORATION PLC

(an Irish public limited company)

2,767,177 Ordinary Shares

UNDERWRITING AGREEMENT

Dated: January 29, 2014

PROTHENA CORPORATION PLC

(an Irish public limited company)

2,767,177 Ordinary Shares

($0.01 nominal value per share)

UNDERWRITING AGREEMENT

January 29, 2014

▇▇▇▇▇▇▇ Lynch, Pierce, ▇▇▇▇▇▇ & ▇▇▇▇▇

Incorporated

Citigroup Global Markets Inc.

as Representatives of the several Underwriters

c/o Merrill Lynch, Pierce, ▇▇▇▇▇▇ & ▇▇▇▇▇

Incorporated

▇▇▇ ▇▇▇▇▇▇ ▇▇▇▇

▇▇▇ ▇▇▇▇, ▇▇▇ ▇▇▇▇ ▇▇▇▇▇

And

c/o Citigroup Global Markets Inc.

▇▇▇ ▇▇▇▇▇▇▇▇▇ ▇▇▇▇▇▇

▇▇▇ ▇▇▇▇, ▇▇▇ ▇▇▇▇ ▇▇▇▇▇

Ladies and Gentlemen:

Prothena Corporation plc, an Irish public limited company (the “Company”), and the entity listed on Schedule B hereto (the “Selling Shareholder”), confirm their respective agreements with ▇▇▇▇▇▇▇ Lynch, Pierce, ▇▇▇▇▇▇ & ▇▇▇▇▇ Incorporated (“▇▇▇▇▇▇▇ ▇▇▇▇▇”), Citigroup Global Markets Inc. (“Citigroup”) and each of the other Underwriters named in Schedule A hereto (collectively, the “Underwriters,” which term shall also include any underwriter substituted as hereinafter provided in Section 10 hereof), for whom ▇▇▇▇▇▇▇ ▇▇▇▇▇ and Citigroup are acting as representatives (in such capacity, the “Representatives”), with respect to (i) the sale by the Selling Shareholder and the purchase by the Underwriters, acting severally and not jointly, of the respective numbers of Ordinary Shares, par value $0.01 per share, of the Company (“Ordinary Shares”) set forth in Schedules A and B hereto and (ii) the grant by the Selling Shareholder to the Underwriters, acting severally and not jointly, of the option described in Section 2(b) hereof to purchase all or any part of 415,076 additional Ordinary Shares from the Selling Shareholder. The aforesaid 2,767,177 Ordinary Shares (the “Initial Securities”) to be purchased by the Underwriters and all or any part of the 415,076 Ordinary Shares, to be purchased by the Underwriters, subject to the option described in Section 2(b) hereof (the “Option Securities”) are herein called, collectively, the “Securities.”

The Company and the Selling Shareholder understand that the Underwriters propose to make a public offering of the Securities as soon as the Representatives deem advisable after this Agreement has been executed and delivered.

The Company has prepared and filed with the Securities and Exchange Commission (the “Commission”) a registration statement on Form S-3 (File No. 333-193416) covering the registration of the sale of the Securities under the Securities Act of 1933, as amended (the “1933 Act”) and the rules and regulations of the Commission under the 1933 Act (the “1933 Act Regulations”), which registration statement was declared effective on January 24, 2014. Such registration statement, as of any time, means such registration statement as amended on the date it was declared effective or by any post-effective amendments thereto to such time, including the exhibits and any schedules thereto at such time, the documents incorporated or deemed to be incorporated by reference therein at such time pursuant to Item 12 of Form S-3 under the 1933 Act and the documents otherwise deemed to be a part thereof as of such time pursuant to Rule 430B under the 1933 Act Regulations (“Rule 430B”), and is referred to herein as the “Registration Statement;” provided, however, that the “Registration Statement” without reference to a time means such registration statement as amended by any post-effective amendments thereto as of the time of the first contract of sale for the Securities, which time shall be considered the “new effective date” of such registration statement with respect to the Securities within the meaning of paragraph (f)(2) of Rule 430B, including the exhibits and schedules thereto as of such time, the documents incorporated or deemed incorporated by reference therein at such time pursuant to Item 12 of Form S-3 under the 1933 Act and the documents otherwise deemed to be a part thereof as of such time pursuant to Rule 430B. Any registration statement filed pursuant to Rule 462(b) of the 1933 Act Regulations is herein called the “Rule 462(b) Registration Statement” and, after such filing, the term “Registration Statement” shall include the Rule 462(b) Registration Statement. Each preliminary prospectus (including any preliminary prospectus supplement) used in connection with the offering of the Securities, including the documents incorporated or deemed to be incorporated by reference therein pursuant to Item 12 of Form S-3 under the 1933 Act, are collectively referred to herein as a “preliminary prospectus.” Promptly after the execution and delivery of this Agreement, the Company will prepare and file a final prospectus relating to the Securities in accordance with the provisions of Rule 424(b) under the 1933 Act Regulations (“Rule 424(b)”). The final prospectus, in the form first furnished or made available to the Underwriters for use in connection with the offering of the Securities, including the documents incorporated or deemed to be incorporated by reference therein pursuant to Item 12 of Form S-3 under the 1933 Act, are collectively referred to herein as the “Prospectus.” For purposes of this Agreement, all references to the Registration Statement, any preliminary prospectus, the Prospectus or any amendment or supplement to any of the foregoing shall be deemed to include the copy filed with the Commission pursuant to its Electronic Data Gathering, Analysis and Retrieval system or any successor system (“▇▇▇▇▇”).

As used in this Agreement:

“Applicable Time” means 1:00 A.M., New York City time, on January 29, 2014, or such other time as agreed by the Company, ▇▇▇▇▇▇▇ ▇▇▇▇▇ and Citigroup.

“General Disclosure Package” means any Issuer General Use Free Writing Prospectuses issued at or prior to the Applicable Time, the most recent preliminary prospectus (including any documents incorporated or deemed to be incorporated by reference therein pursuant to Item 12 of Form S-3 under the ▇▇▇▇ ▇▇▇) that is distributed to investors prior to the Applicable Time, and the information included on Schedule C-1 hereto, all considered together.

“Issuer Free Writing Prospectus” means any “issuer free writing prospectus,” as defined in Rule 433 of the 1933 Act Regulations (“Rule 433”), including without limitation any “free writing prospectus” (as defined in Rule 405 of the 1933 Act Regulations (“Rule 405”)) relating to the Securities that is (i) required to be filed with the Commission by the Company, (ii) a “road show that is a written communication” within the meaning of Rule 433(d)(8)(i), whether or not required to be filed with the Commission, or (iii) exempt from filing with the Commission pursuant to Rule 433(d)(5)(i) because it contains a description of the Securities or of the offering that does not reflect the final terms, in each case in the form filed or required to be filed with the Commission or, if not required to be filed, in the form retained in the Company’s records pursuant to Rule 433(g).

“Issuer General Use Free Writing Prospectus” means any Issuer Free Writing Prospectus that is intended for general distribution to prospective investors, as evidenced by its being specified in Schedule C-2 hereto.

“Issuer Limited Use Free Writing Prospectus” means any Issuer Free Writing Prospectus that is not an Issuer General Use Free Writing Prospectus.

“Testing-the-Waters Communication” means any oral or written communication with potential investors undertaken in reliance on Section 5(d) of the 1933 Act.

“Written Testing-the-Waters Communication” means any Testing-the-Waters Communication that is a written communication within the meaning of Rule 405 under the 1933 Act.

All references in this Agreement to financial statements and schedules and other information which is “contained,” “included” or “stated” (or other references of like import) in the Registration Statement, any preliminary prospectus or the Prospectus shall be deemed to include all such financial statements and schedules and other information incorporated or deemed incorporated by reference in the Registration Statement, any preliminary prospectus or the Prospectus, as the case may be, prior to the execution and delivery of this Agreement; and all references in this Agreement to amendments or supplements to the Registration Statement, any preliminary prospectus or the Prospectus shall be deemed to include the filing of any document under the Securities Exchange Act of 1934, as amended (the “1934 Act”), and the rules and regulations promulgated thereunder (the “1934 Act Regulations”), incorporated or deemed to be incorporated by reference in the Registration Statement, such preliminary prospectus or the Prospectus, as the case may be, at or after the execution and delivery of this Agreement.

SECTION 1. Representations and Warranties.

(a) Representations and Warranties by the Company. The Company represents and warrants to each Underwriter as of the date hereof, the Applicable Time, the Closing Time (as defined below) and any Date of Delivery (as defined below), and agrees with each Underwriter, as follows:

(i) Registration Statement and Prospectuses. The Company meets the requirements for use of Form S-3 under the 1933 Act. Each of the Registration Statement and any amendment thereto has become effective under the 1933 Act. No stop order suspending the effectiveness of the Registration Statement or any post-effective amendment thereto has been issued under the 1933 Act, no order preventing or suspending the use of any preliminary prospectus or the Prospectus has been issued and no proceedings for any of those purposes have been instituted or are pending or, to the Company’s knowledge, contemplated. The Company has complied with each request (if any) from the Commission for additional information.

Each of the Registration Statement and any post-effective amendment thereto, at the time of its effectiveness and at each deemed effective date with respect to the Underwriters pursuant to Rule 430B(f)(2) under the 1933 Act Regulations, complied in all material respects with the requirements of the 1933 Act and the 1933 Act Regulations. Each preliminary prospectus, the Prospectus and any amendment or supplement thereto, at the time each was filed with the Commission, complied in all material respects with the requirements of the 1933 Act and the 1933 Act Regulations. Each preliminary prospectus delivered to the Underwriters for use in connection with this offering and the Prospectus was or will be identical to the electronically transmitted copies thereof filed with the Commission pursuant to ▇▇▇▇▇, except to the extent permitted by Regulation S-T.

The documents incorporated or deemed to be incorporated by reference in the Registration Statement, any preliminary prospectus and the Prospectus, when they became effective or at the time they were or hereafter are filed with the Commission, complied and will comply in all material respects with the requirements of the 1934 Act and the 1934 Act Regulations.

(ii) Accurate Disclosure. Neither the Registration Statement nor any amendment thereto, at its effective time, at the Closing Time or at any Date of Delivery, contained, contains or will contain an untrue statement of a material fact or omitted, omits or will omit to state a material fact required to be stated therein or necessary to make the statements therein not misleading. As of the Applicable Time, neither (A) the General Disclosure Package nor (B) any individual Issuer Limited Use Free Writing Prospectus, when considered together with the General Disclosure Package, included, includes or will include an untrue statement of a material fact or omitted, omits or will omit to state a material fact necessary in order to make the statements therein, in the light of the circumstances under which they were made, not misleading. Neither the Prospectus nor any amendment or supplement thereto (including any prospectus wrapper), as of its issue date, at the time of any filing with the Commission pursuant to Rule 424(b), at the Closing Time or at any Date of Delivery, included, includes or will include an untrue statement of a material fact or omitted, omits or will omit to state a material fact necessary in order to make the statements therein, in the light of the circumstances under which they were made, not misleading. The documents incorporated or deemed to be incorporated by reference in the Registration Statement, the General Disclosure Package and the Prospectus, at the time the Registration Statement became effective or when such documents incorporated by reference were or hereafter are filed with the Commission, as the case may be, when read together with the other information in the Registration Statement, the General Disclosure Package or the Prospectus, as the case may be, did not and will not include an 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.

The representations and warranties in this subsection shall not apply to statements in or omissions from the Registration Statement (or any amendment thereto), the General Disclosure Package or the Prospectus (or any amendment or supplement thereto) made in reliance upon and in conformity with written information furnished to the Company by any Underwriter through ▇▇▇▇▇▇▇ ▇▇▇▇▇ or Citigroup expressly for use therein. For purposes of this Agreement, the only information so furnished shall be the

information in the first paragraph under the heading “Underwriting–Commissions and Discounts,” the information in the second, third and fourth paragraphs under the heading “Underwriting–Price Stabilization, Short Positions” and the information under the heading “Underwriting–Electronic Distribution,” in each case contained in the Prospectus (collectively, the “Underwriter Information”).

(iii) Issuer Free Writing Prospectuses. No Issuer Free Writing Prospectus conflicts or will conflict with the information contained in the Registration Statement or the Prospectus, including any document incorporated by reference therein, and any preliminary or other prospectus deemed to be a part thereof that has not been superseded or modified.

(iv) Testing-the-Waters Materials. The Company (A) has not engaged in any Testing-the-Waters Communication and (B) has not authorized anyone other than the Representatives to engage in Testing-the-Waters Communications. The Company reconfirms that the Representatives have been authorized to act on its behalf in undertaking Testing-the-Waters Communications.

(v) Company Not Ineligible Issuer. At the time of filing the Registration Statement and any post-effective amendment thereto, at the earliest time thereafter that the Company or another offering participant made a bona fide offer (within the meaning of Rule 164(h)(2) of the 1933 Act Regulations) of the Securities and at the date hereof, the Company was not and is not an “ineligible issuer,” as defined in Rule 405, without taking account of any determination by the Commission pursuant to Rule 405 that it is not necessary that the Company be considered an ineligible issuer.

(vi) Emerging Growth Company Status. From the time of the initial filing of the Registration Statement with the Commission (or, if earlier, the first date on which the Company engaged directly or through any Person authorized to act on its behalf in any Testing-the-Waters Communication) through the date hereof, the Company has been and is an “emerging growth company,” as defined in Section 2(a) of the Securities Act (an “Emerging Growth Company”).

(vii) Independent Accountants. The accountants who certified the financial statements and supporting schedules included in the Registration Statement, the General Disclosure Package and the Prospectus are independent public accountants as required by the 1933 Act, the 1933 Act Regulations, the 1934 Act, the 1934 Act Regulations and the Public Company Accounting Oversight Board.

(viii) Financial Statements. The financial statements included or incorporated by reference in the Registration Statement, the General Disclosure Package and the Prospectus, together with the related schedules and notes, present fairly in all material respects the financial position of the Company and its consolidated subsidiaries at the dates indicated and the statement of operations, shareholders’ equity and cash flows of the Company and its consolidated subsidiaries for the periods specified; said financial statements have been prepared in conformity with U.S. generally accepted accounting principles (“GAAP”) applied on a consistent basis throughout the periods involved, provided, however, that prior to the separation of the Prothena business, which consists of a substantial portion of the former drug discovery platform of Elan Corporation, plc (now Elan Corporation Limited) (“Elan”), including Neotope Biosciences Limited and its

wholly owned subsidiaries Onclave Therapeutics Limited and Prothena Biosciences Inc, from Elan on December 20, 2012, the financial statements of the Company have been prepared on a “carve-out” basis from the consolidated financial statements of Elan to represent the financial position and performance of the Company as if it had existed on a stand-alone basis and as if Financial Accounting Standards Board Accounting Standard Codification Topic 810, “Consolidation,” had been applied throughout. The supporting schedules, if any, present fairly in all material respects in accordance with GAAP the information required to be stated therein. The selected financial data and the summary financial information included or incorporated by reference in the Registration Statement, the General Disclosure Package and the Prospectus present fairly in all material respects the information shown therein and have been compiled on a basis consistent with that of the audited financial statements included therein. Except as included therein, no historical or pro forma financial statements or supporting schedules are required to be included or incorporated by reference in the Registration Statement, the General Disclosure Package or the Prospectus under the 1933 Act, the 1933 Act Regulations, the 1934 Act or the 1934 Act Regulations. The interactive data in eXtensible Business Reporting Language included or incorporated by reference in the Registration Statement, the General Disclosure Package and the Prospectus fairly presents in all material respects the information called for and has been prepared in accordance with the Commission’s rules and guidelines applicable thereto.

(ix) No Material Adverse Change in Business. Except as otherwise stated therein, since the respective dates as of which information is given in the Registration Statement, the General Disclosure Package or the Prospectus, (A) there has been no material adverse change in the condition, financial or otherwise, or in the earnings, business affairs or business prospects of the Company and its subsidiaries considered as one enterprise, whether or not arising in the ordinary course of business (a “Material Adverse Effect”), (B) there have been no transactions entered into by the Company or any of its subsidiaries, other than those in the ordinary course of business, which are material with respect to the Company and its subsidiaries considered as one enterprise, and (C) there has been no dividend or distribution of any kind declared, paid or made by the Company on any class of its share capital.

(x) Due Incorporation of the Company. The Company has been duly incorporated and is validly existing as a public limited company by shares under the laws of the Republic of Ireland and has corporate power and authority to own, lease and operate its properties and to conduct its business as described in the Registration Statement, the General Disclosure Package and the Prospectus and to enter into and perform its obligations under this Agreement; and the Company is duly qualified as a foreign corporation to transact business and is in good standing in each other jurisdiction in which such qualification is required (or such equivalent concept to the extent it exists under the laws of such jurisdiction), whether by reason of the ownership or leasing of property or the conduct of business, except where the failure so to qualify or to be in good standing would not result in a Material Adverse Effect.

(xi) Due Incorporation and Good Standing of Subsidiaries. Each “significant subsidiary” of the Company (as such term is defined in Rule 1-02 of Regulation S-X, which, for the avoidance of doubt, shall include Neotope Biosciences Limited, Onclave Therapeutics Limited and Prothena Biosciences Inc) (each, a “Subsidiary” and,

collectively, the “Subsidiaries”) has been duly incorporated or organized and is validly existing in good standing (or such equivalent concept to the extent it exists under the laws of such jurisdiction) under the laws of the jurisdiction of its incorporation or organization, has corporate or similar power and authority to own, lease and operate its properties and to conduct its business as described in the Registration Statement, the General Disclosure Package and the Prospectus and is duly qualified to transact business and is in good standing in each 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 so qualify or to be in good standing would not result in a Material Adverse Effect. Except as otherwise disclosed in the Registration Statement, the General Disclosure Package and the Prospectus, all of the issued and outstanding capital stock or share capital of each Subsidiary has been duly authorized and validly issued, is fully paid and not subject to calls for any additional payments (non-assessable) and is owned by the Company, directly or through subsidiaries, free and clear of any security interest, mortgage, pledge, lien, encumbrance, claim or equity. None of the outstanding shares of capital stock or share capital of any Subsidiary were issued in violation of the preemptive or similar rights of any securityholder of such Subsidiary. The only subsidiaries of the Company are the subsidiaries listed on Exhibit 21.1 to the Company’s Annual Report on Form 10-K for the fiscal year ended December 31, 2012.

(xii) Capitalization. The authorized and issued share capital of the Company are as set forth in the Registration Statement, the General Disclosure Package and the Prospectus (except for subsequent issuances, if any, pursuant to this Agreement, pursuant to reservations, agreements, employee benefit or equity incentive plans referred to in the Registration Statement, the General Disclosure Package and the Prospectus or pursuant to the exercise of convertible securities or options referred to in the Registration Statement, the General Disclosure Package and the Prospectus). The issued share capital of the Company, including the Securities to be purchased by the Underwriters from the Selling Shareholder, have been duly authorized, validly issued and are fully paid and not subject to calls for any additional payments (non-assessable). None of the issued share capital of the Company, including the Securities to be purchased by the Underwriters from the Selling Shareholder, were issued in violation of the preemptive or other similar rights of any shareholder of the Company.

(xiii) Authorization of Agreement. This Agreement has been duly authorized, executed and delivered by the Company.

(xiv) Authorization and Description of Securities. The Ordinary Shares conform in all material respects to all statements relating thereto contained in the Registration Statement, the General Disclosure Package and the Prospectus and such description conforms to the rights set forth in the instruments defining the same. No holder of Securities will be subject to personal liability solely by reason of being such a holder.

(xv) Registration Rights. There are no persons with registration rights or other similar rights to have any Ordinary Shares registered for sale pursuant to the Registration Statement or otherwise registered for sale or sold by the Company under the 1933 Act pursuant to this Agreement, other than those rights that have been disclosed in the Registration Statement, the General Disclosure Package and the Prospectus.

(xvi) Absence of Violations, Defaults and Conflicts. Neither the Company nor any of its subsidiaries is (A) in violation of its Memorandum and Articles of Association, charter, by-laws or similar organizational document, (B) in default in the performance or observance of any obligation, agreement, covenant or condition contained in any contract, indenture, mortgage, deed of trust, loan or credit agreement, note, lease or other agreement or instrument to which the Company or any of its subsidiaries is a party or by which it or any of them may be bound or to which any of the properties or assets of the Company or any subsidiary is subject (collectively, “Agreements and Instruments”), except for such defaults that would not, singly or in the aggregate, result in a Material Adverse Effect, or (C) in violation of any law, statute, rule, regulation, judgment, order, writ or decree of any arbitrator, court, governmental body, regulatory body, administrative agency or other authority, body or agency having jurisdiction over the Company or any of its subsidiaries or any of their respective properties, assets or operations (each, a “Governmental Entity”), except for such violations that would not, singly or in the aggregate, result in a Material Adverse Effect. The execution, delivery and performance of this Agreement and the consummation of the transactions contemplated herein and in the Registration Statement, the General Disclosure Package and the Prospectus and compliance by the Company with its obligations hereunder have been duly authorized by all necessary corporate action and do not and will not, whether with or without the giving of notice or passage of time or both, conflict with or constitute a breach of, or default or Repayment Event (as defined below) under, or result in the creation or imposition of any lien, charge or encumbrance upon any properties or assets of the Company or any subsidiary pursuant to, the Agreements and Instruments (except for such conflicts, breaches, defaults or Repayment Events or liens, charges or encumbrances that would not, singly or in the aggregate, result in a Material Adverse Effect), nor will such action result in (i) any violation of the provisions of the Memorandum and Articles of Association, charter, by-laws or similar organizational document of the Company or any of its subsidiaries or (ii) any law, statute, rule, regulation, judgment, order, writ or decree of any Governmental Entity, except in the case of clause (ii) for such violations as would not, singly or in the aggregate, result in a Material Adverse Effect. As used herein, a “Repayment Event” means any event or condition which gives the holder of any note, debenture or other evidence of indebtedness (or any person acting on such holder’s behalf) the right to require the repurchase, redemption or repayment of all or a portion of such indebtedness by the Company or any of its subsidiaries.

(xvii) Absence of Labor Dispute. No labor dispute with the employees of the Company or any of its subsidiaries exists or, to the knowledge of the Company, is imminent, and the Company is not aware of any existing or imminent labor disturbance by the employees of any of its or any subsidiary’s principal suppliers, manufacturers, customers or contractors, which, in either case, would reasonably be expected to result in a Material Adverse Effect.

(xviii) Absence of Proceedings. Except as disclosed in the Registration Statement, the General Disclosure Package and the Prospectus, there is no action, suit, proceeding, inquiry or investigation before or brought by any Governmental Entity now pending or, to the knowledge of the Company, threatened, against or affecting the Company or any of its subsidiaries, which would reasonably be expected to result in a Material Adverse Effect, or which would reasonably be expected to materially and

adversely affect their respective properties or assets or the consummation of the transactions contemplated in this Agreement or the performance by the Company of its obligations hereunder; and the aggregate of all pending legal or governmental proceedings to which the Company or any such subsidiary is a party or of which any of their respective properties or assets is the subject which are not described in the Registration Statement, the General Disclosure Package and the Prospectus, including ordinary routine litigation incidental to the business, would not reasonably be expected to result in a Material Adverse Effect.

(xix) Accuracy of Exhibits. There are no contracts or documents which are required to be described in the Registration Statement, the General Disclosure Package or the Prospectus or to be filed as exhibits to the Registration Statement which have not been so described and filed as required.

(xx) Absence of Further Requirements. No filing with, or authorization, approval, consent, license, order, registration, qualification or decree of, any Governmental Entity is necessary or required for the performance by the Company of its obligations hereunder, in connection with the offering of the Securities hereunder or the consummation of the transactions contemplated by this Agreement, except such as have been already obtained or as may be required under the 1933 Act, the 1933 Act Regulations, the rules of the NASDAQ Stock Market LLC, state securities laws, the laws of the Republic of Ireland or the rules of the Financial Industry Regulatory Authority, Inc. (“FINRA”).

(xxi) Regulatory Matters; Possession of Licenses and Permits. Except as described in the Registration Statement, the General Disclosure Package and the Prospectus, and except as would not, individually or in the aggregate, result in a Material Adverse Effect: (i) the Company has not received any FDA Form 483 notice of adverse finding, warning letter or other written correspondence or notice from the U.S. Food and Drug Administration (“FDA”) or any other Governmental Entity alleging or asserting noncompliance with any Applicable Laws (as defined in clause (ii) below) or Authorizations (as defined in clause (iii) below); (ii) the Company is and has been in compliance with statutes, laws, ordinances, rules and regulations applicable to the Company for the ownership, testing, development, manufacture, packaging, processing, use, labeling, promotion, storage, import, export or disposal of any product manufactured or distributed by the Company, including without limitation, the Federal Food, Drug, and Cosmetic Act, 21 U.S.C. § 301, et seq., similar laws of other Governmental Entities and the regulations promulgated pursuant to such laws (collectively, “Applicable Laws”); (iii) the Company possesses all licenses, certificates, approvals, authorizations, permits and supplements or amendments thereto required by any such Applicable Laws and/or for the ownership of its properties or the conduct of its business as described in the Registration Statement, the General Disclosure Package and the Prospectus (collectively, “Authorizations”) and such Authorizations are valid and in full force and effect and the Company is not in violation of any term of any such Authorizations; (iv) the Company has not received written notice of any ongoing claim, action, suit, proceeding, hearing, enforcement, investigation, arbitration or other action from any Governmental Entity or third party alleging that any product, operation or activity is in violation of any Applicable Laws or Authorizations, and to the Company’s knowledge, no such Governmental Entity or third party has threatened any such claim, litigation, arbitration,

action, suit, investigation or proceeding; (v) the Company has not received written notice that any Governmental Entity has taken, is taking or intends to take action to limit, suspend, adversely modify or revoke any Authorizations and to the Company’s knowledge, no such Governmental Entity has threatened or intends to take such action; and (vi) the Company has filed, obtained, maintained or submitted all reports, documents, forms, notices, applications, records, claims, submissions and supplements or amendments (“Submissions”) as required by any Applicable Laws or Authorizations and all such Submissions were true, complete, correct on the date filed (or were corrected, updated, modified, or supplemented by a subsequent Submission). Neither the Company nor, to the Company’s knowledge, any of its directors, officers, employees or agents has been convicted of any crime under the federal Food, Drug and Cosmetic Act or comparable laws of other Governmental Entities that could result in a material debarment or exclusion under 21 U.S.C. Section 335a or any similar Applicable Law, and neither the Company nor, to the Company’s knowledge, any of its directors, officers, employees or agents has been the subject of an FDA debarment proceeding. The Company has not been nor is it now the subject of any pending or, to the knowledge of the Company, threatened investigation by the FDA pursuant to its “Fraud, Untrue Statements of Material Facts, Bribery, and Illegal Gratuities” Final Policy set forth in 56 Fed. Reg. 46191 (September 10, 1991).

(xxii) Studies and Tests. The preclinical and clinical studies and tests conducted by or, to the knowledge of the Company, on behalf of the Company and its subsidiaries have been and, if still pending, are being conducted in all material respects in accordance with experimental protocols, procedures and controls pursuant to all Applicable Laws and Authorizations; the descriptions of the results of such preclinical and clinical studies and tests contained in the Registration Statement, the General Disclosure Package and the Prospectus are accurate and complete in all material respects and fairly present the data derived from such preclinical and clinical studies and tests; except to the extent disclosed in the Registration Statement, the General Disclosure Package and the Prospectus, the Company is not aware of any preclinical or clinical studies or tests, the results of which the Company believes reasonably call into question the research, preclinical or clinical study or test results described or referred to in the Registration Statement, the General Disclosure Package and the Prospectus when viewed in the context in which such results are described; and the Company has not received any written notices or correspondence from any Governmental Entity requiring the termination, suspension or material modification of any preclinical or clinical study or test conducted by or on behalf of the Company or its subsidiaries, as applicable.

(xxiii) Title to Property. The Company and its subsidiaries have good and marketable title to all real property owned by them and good title to all other properties owned by them, in each case, free and clear of all mortgages, pledges, liens, security interests, claims, restrictions or encumbrances of any kind except such as (A) are described in the Registration Statement, the General Disclosure Package and the Prospectus or (B) do not, singly or in the aggregate, materially affect the value of such property and do not interfere with the use made and proposed to be made of such property by the Company or any of its subsidiaries; and all of the leases and subleases material to the business of the Company and its subsidiaries, considered as one enterprise, and under which the Company or any of its subsidiaries holds properties described in the Registration Statement, the General Disclosure Package or the

Prospectus, are in full force and effect, and neither the Company nor any such subsidiary has any notice of any claim of any sort that has been asserted by anyone adverse to the rights of the Company or any subsidiary under any of the leases or subleases mentioned above, or affecting or questioning the rights of the Company or such subsidiary to the continued possession of the leased or subleased premises under any such lease or sublease, except for such claims as would not, singly or in the aggregate, result in a Material Adverse Effect.

(xxiv) Possession of Intellectual Property. The Company and its subsidiaries own or possess, have licenses to, or can acquire licenses on reasonable terms to, adequate patents, patent rights, inventions, copyrights, know-how (including trade secrets and other unpatented and/or unpatentable proprietary or confidential information, systems or procedures), trademarks, service marks, trade names or other intellectual property (collectively, “Intellectual Property”) necessary to carry on the business now operated by them and, to the knowledge of the Company, as proposed to be conducted as disclosed in the Registration Statement, the General Disclosure Package and the Prospectus, and neither the Company nor any of its subsidiaries has received any notice or is otherwise aware (A) of any infringement of or conflict with asserted rights of others with respect to any Intellectual Property arising by the Company’s and its subsidiaries’ business as now operated by them or (B) of any facts or circumstances which would render any issued patents within the Intellectual Property owned or licensed by the Company or any of its subsidiaries invalid, and in each case (A) and (B) which infringement or conflict (if the subject of any unfavorable decision, ruling or finding) or invalidity, singly or in the aggregate, would result in a Material Adverse Effect.

(xxv) Environmental Laws. Except as described in the Registration Statement, the General Disclosure Package and the Prospectus or would not, singly or in the aggregate, result in a Material Adverse Effect, (A) neither the Company nor any of its subsidiaries is in violation of any federal, state, local or foreign statute, law, rule, regulation, ordinance, code, policy or rule of common law or any judicial or administrative interpretation thereof, including any judicial or administrative order, consent, decree or judgment, relating to pollution or protection of human health, 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 the release or threatened release of chemicals, pollutants, contaminants, wastes, toxic substances, hazardous substances, petroleum or petroleum products, asbestos-containing materials or mold (collectively, “Hazardous Materials”) or to the manufacture, processing, distribution, use, treatment, storage, disposal, transport or handling of Hazardous Materials (collectively, “Environmental Laws”), (B) the Company and its subsidiaries have all permits, authorizations and approvals required for their operation under any applicable Environmental Laws and are each in compliance with their requirements, (C) there are no pending or, to the knowledge of the Company, threatened administrative, regulatory or judicial actions, suits, demands, demand letters, claims, liens, notices of noncompliance or violation, investigation or proceedings relating to any Environmental Law against the Company or any of its subsidiaries and (D) to the knowledge of the Company, there are no events or circumstances existing as of the date hereof that would reasonably be expected to form the basis of an order for clean-up or remediation, or an action, suit or proceeding by any private party or Governmental Entity, against or affecting the Company or any of its subsidiaries relating to Hazardous Materials or any Environmental Laws.

(xxvi) Accounting Controls and Disclosure Controls. The Company and each of its subsidiaries maintain effective internal control over financial reporting (as defined under Rule 13-a15 and 15d-15 under the 1934 Act Regulations) and a system of internal accounting controls sufficient to provide reasonable assurances that (A) transactions are executed in accordance with management’s general or specific authorization; (B) transactions are recorded as necessary to permit preparation of financial statements in conformity with GAAP and to maintain accountability for assets; (C) access to assets is permitted only in accordance with management’s general or specific authorization; (D) the recorded accountability for assets is compared with the existing assets at reasonable intervals and appropriate action is taken with respect to any differences; and (E) the interactive data in eXtensible Business Reporting Language included or incorporated by reference in the Registration Statement, the General Disclosure Package and the Prospectus fairly presents in all material respects the information called for and is prepared in accordance with the Commission’s rules and guidelines applicable thereto. Except as described in the Registration Statement, the General Disclosure Package and the Prospectus, since the end of the Company’s most recent audited fiscal year, there has been (1) no material weakness in the Company’s internal control over financial reporting (whether or not remediated) and (2) no change in the Company’s internal control over financial reporting that has materially and adversely affected, or is reasonably likely to materially and adversely affect, the Company’s internal control over financial reporting. The Company and each of its subsidiaries maintain an effective system of disclosure controls and procedures (as defined in Rule 13a-15 and Rule 15d-15 under the 1934 Act Regulations) that are designed to ensure that information required to be disclosed by the Company in the reports that it files or submits under the 1934 Act is recorded, processed, summarized and reported, within the time periods specified in the Commission’s rules and forms, and is accumulated and communicated to the Company’s management, including its principal executive officer or officers and principal financial officer or officers, as appropriate, to allow timely decisions regarding disclosure.

(xxvii) Compliance with the ▇▇▇▇▇▇▇▇-▇▇▇▇▇ Act. The Company is in compliance in all material respects with the ▇▇▇▇▇▇▇▇-▇▇▇▇▇ Act of 2002 and the rules and regulations promulgated in connection therewith (the “▇▇▇▇▇▇▇▇-▇▇▇▇▇ Act”) with which it must comply as of the date hereof, including Section 402 related to loans and Sections 302 and 906 related to certifications.

(xxviii) Payment of Taxes. All United States federal income tax returns of the Company and its subsidiaries required by law to be filed have been filed and all taxes shown by such returns or otherwise assessed, which are due and payable, have been paid, except assessments against which appeals have been or will be promptly taken and as to which adequate reserves have been provided. The Company and its subsidiaries have filed all other tax returns that are required to have been filed by them pursuant to applicable foreign, state, local or other law except insofar as the failure to file such returns would not result in a Material Adverse Effect, and has paid all taxes due pursuant to such returns or pursuant to any assessment received by the Company and its subsidiaries, except for such taxes, if any, as are being contested in good faith and as to which adequate reserves have been established by the Company and except where the

failure to pay such taxes would not result in a Material Adverse Effect. The charges, accruals and reserves on the books of the Company in respect of any income and corporation tax liability for any years not finally determined are adequate to meet any assessments or re-assessments for additional income tax for any years not finally determined, except to the extent of any inadequacy that would not result in a Material Adverse Effect.

(xxix) Transfer Taxes. Except as described in the Registration Statement, the General Disclosure Package and the Prospectus, there are no transfer taxes or other similar fees or charges under Irish or Federal law or the laws of any state, or any political subdivision thereof, required to be paid in connection with the execution and delivery of this Agreement.

(xxx) Insurance. Except as described in the Registration Statement, the General Disclosure Package and the Prospectus, the Company and its subsidiaries carry or are entitled to the benefits of insurance, with financially sound and reputable insurers, in such amounts and covering such risks as is generally maintained by companies of established repute engaged in the same or similar business, and all such insurance is in full force and effect. The Company has no reason to believe that it or any of its subsidiaries will not be able (A) to renew its existing insurance coverage as and when such policies expire or (B) 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 Effect. Neither of the Company nor any of its subsidiaries has been denied any insurance coverage which it has sought or for which it has applied.

(xxxi) Investment Company Act. The Company is not required, and upon the consummation of the transactions contemplated herein, will not be required, to register as an “investment company” under the Investment Company Act of 1940, as amended (the “1940 Act”).

(xxxii) Absence of Manipulation. Neither the Company nor any affiliate of the Company has taken, nor will the Company or any affiliate take, directly or indirectly, without giving effect to activities by the Underwriters, any action which is designed, or would reasonably be expected, to cause or result in, or which constitutes, the stabilization or manipulation of the price of any security of the Company to facilitate the issue or sale or resale of the Securities or to result in a violation of Regulation M under the 1934 Act. For purposes of this Agreement, the Selling Shareholder shall not be considered an affiliate of the Company.

(xxxiii) Anti-Bribery Laws. None of the Company, any of its subsidiaries or, to the knowledge of the Company, any director, officer, agent, employee, affiliate or other person acting on behalf of the Company or any of its subsidiaries is aware of or has taken any action, directly or indirectly, that would result in a violation by such persons of any anti-bribery law (including, without limitation, the Foreign Corrupt Practices Act of 1977, as amended, and the rules and regulations thereunder (the “FCPA”) and the UK Bribery Act 2010), including, without limitation, making use of the mails or any means or instrumentality of interstate commerce corruptly in furtherance of an offer, payment, promise to pay or authorization of the payment of any money, or other property, gift, promise to give, or authorization of the giving of anything of value to any “foreign

official” (as such term is defined in the FCPA) or any foreign political party or official thereof or any candidate for foreign political office, in contravention of the FCPA or the UK ▇▇▇▇▇▇▇ ▇▇▇ ▇▇▇▇ and the Company and, to the knowledge of the Company, its affiliates have conducted their businesses in compliance with the FCPA and the UK ▇▇▇▇▇▇▇ ▇▇▇ ▇▇▇▇ and have instituted and maintain policies and procedures designed to ensure, and which are reasonably expected to continue to ensure, continued compliance therewith.

(xxxiv) Money Laundering Laws. The operations of the Company and its subsidiaries are and have been conducted at all times in compliance in all material respects with applicable financial recordkeeping and reporting requirements of the Currency and Foreign Transactions Reporting Act of 1970, as amended, the money laundering statutes of all jurisdictions, the rules and regulations thereunder and any related or similar rules, regulations or guidelines, issued, administered or enforced by any Governmental Entity (collectively, the “Money Laundering Laws”); and no action, suit or proceeding by or before any Governmental Entity involving the Company or any of its subsidiaries with respect to the Money Laundering Laws is pending or, to the knowledge of the Company, threatened.

(xxxv) OFAC. None of the Company, any of its subsidiaries or, to the knowledge of the Company, any director, officer, agent, employee, affiliate or representative of the Company or any of its subsidiaries is an individual or entity (“Person”) currently the subject or target of any sanctions administered or enforced by the United States Government, including, without limitation, the U.S. Department of the Treasury’s Office of Foreign Assets Control (“OFAC”), the United Nations Security Council (“UNSC”), the European Union, Her Majesty’s Treasury (“HMT”), or other relevant sanctions authority (collectively, “Sanctions”), nor is the Company located, organized or resident in a country or territory that is the subject of Sanctions.

(xxxvi) Lending Relationship. Except as disclosed in the Registration Statement, the General Disclosure Package and the Prospectus, the Company does not have any material lending or other relationship with any bank or lending affiliate of any Underwriter.

(xxxvii) Statistical and Market-Related Data. Any statistical and market-related data included in the Registration Statement, the General Disclosure Package or the Prospectus are based on or derived from sources that the Company believes to be reliable and accurate.

(xxxviii) Maintenance of Rating. The Company has no debt securities or preferred stock that is rated by any “nationally recognized statistical rating organization” (as such term is defined in Section 3(a)(62) of the 1934 Act).

(b) Representations and Warranties by the Selling Shareholder. The Selling Shareholder represents and warrants to each Underwriter as of the date hereof, as of the Applicable Time, as of the Closing Time and, if the Selling Shareholder is selling Option Securities on a Date of Delivery, as of each such Date of Delivery, and agrees with each Underwriter, as follows:

(i) Accurate Disclosure. Neither the General Disclosure Package nor the Prospectus (in each case together with any amendments or supplements thereto) includes or will include any untrue statement of a material fact or omits to state a material fact necessary in order to make the statements therein, in the light of the circumstances under which they were made, not misleading, provided that this representation and warranty applies only to statements or omissions made in reliance upon and in conformity with information relating to the Selling Shareholder furnished in writing by or on behalf of the Selling Shareholder expressly for use in the Registration Statement, the General Disclosure Package, the Prospectus or any other Issuer Free Writing Prospectus or any amendment or supplement thereto (the “Selling Shareholder Information”), it being understood and agreed that for all purposes of this Agreement, the Selling Shareholder Information consists only of the statements pertaining to the name and address of the Selling Shareholder and the number of Ordinary Shares owned by the Selling Shareholder under the captions “Selling Shareholder” or “Selling Shareholders” (including, for the avoidance of doubt, such information set forth in the footnotes to the beneficial ownership table under the captions “Selling Shareholder” or “Selling Shareholders”) as set forth in the Registration Statement, the General Disclosure Package and the Prospectus; the Selling Shareholder is not prompted to sell the Securities to be sold by the Selling Shareholder hereunder by any material non-public information concerning the Company or any subsidiary of the Company which is not set forth in the General Disclosure Package or the Prospectus.

(ii) Authorization of this Agreement. This Agreement has been duly authorized, executed and delivered by or on behalf of the Selling Shareholder.

(iii) Noncontravention. The execution and delivery of this Agreement and the sale and delivery of the Securities to be sold by the Selling Shareholder and the consummation by the Selling Shareholder of the transactions contemplated herein and compliance by the Selling Shareholder with its obligations hereunder do not and will not (A) conflict with or constitute a breach of, or default under, or result in the creation or imposition of any tax, lien, charge or encumbrance upon the Securities to be sold by the Selling Shareholder or any property or assets of the Selling Shareholder pursuant to, whether with or without the giving of notice or passage of time or both, any contract, indenture, mortgage, deed of trust, loan or credit agreement, note, license, lease or other agreement or instrument to which the Selling Shareholder is a party or by which the Selling Shareholder may be bound, or to which any of the property or assets of the Selling Shareholder is subject, (B) result in any violation of the provisions of the Memorandum and Articles of Association, as amended, of the Selling Shareholder or (C) result in any violation of any applicable treaty, law, statute, rule, regulation, judgment, order, writ or decree of any government, government instrumentality or court, domestic or foreign, having jurisdiction over the Selling Shareholder or any of its properties, other than, in the case of clauses (A) and (C), as would not reasonably be expected to have a material adverse effect on the Selling Shareholder’s ability to consummate the transactions contemplated by this agreement.

(iv) Valid Title. The Selling Shareholder has, and at the Closing Time will have, valid title to the Securities to be sold by the Selling Shareholder free and clear of all security interests, claims, liens, or other encumbrances and the legal right and power, and all authorization and approval required by law, to enter into this Agreement and to sell, transfer and deliver the Securities to be sold by such Selling Shareholder or a valid security entitlement in respect of such Securities.

(v) Delivery of Securities. Upon payment of the purchase price for the Securities to be sold by the Selling Shareholder pursuant to this Agreement, delivery of such Securities, as directed by the Underwriters, to Cede & Co. (“Cede”) or such other nominee as may be designated by The Depository Trust Company (“DTC”) (unless delivery of such Securities is unnecessary because such Securities are already in possession of Cede or such nominee), registration of such Securities in the name of Cede or such other nominee (unless registration of such Securities is unnecessary because such Securities are already registered in the name of Cede or such nominee), and the crediting of such Securities on the books of DTC to securities accounts (within the meaning of Section 8-501(a) of the UCC) of the Underwriters (assuming that neither DTC nor any such Underwriter has notice of any “adverse claim,” within the meaning of Section 8-105 of the Uniform Commercial Code then in effect in the State of New York (“UCC”), to such Securities), (A) under Section 8-501 of the UCC, the Underwriters will acquire a valid “security entitlement” in respect of such Securities and (B) no action (whether framed in conversion, replevin, constructive trust, equitable lien, or other theory) based on any “adverse claim,” within the meaning of Section 8-102 of the UCC, to such Securities may be asserted against the Underwriters with respect to such security entitlement; for purposes of this representation, the Selling Shareholder may assume that when such payment, delivery (if necessary) and crediting occur, (I) such Securities will have been registered in the name of Cede or another nominee designated by DTC, in each case on the Company’s share registry in accordance with its Amended and Restated Memorandum and Articles of Association and applicable law, (II) DTC will be registered as a “clearing corporation,” within the meaning of Section 8-102 of the UCC, (III) appropriate entries to the accounts of the several Underwriters on the records of DTC will have been made pursuant to the UCC, (IV) to the extent DTC, or any other securities intermediary which acts as “clearing corporation” with respect to the Securities, maintains any “financial asset” (as defined in Section 8-102(a)(9) of the UCC in a clearing corporation pursuant to Section 8-111 of the UCC, the rules of such clearing corporation may affect the rights of DTC or such securities intermediaries and the ownership interest of the Underwriters, (V) claims of creditors of DTC or any other securities intermediary or clearing corporation may be given priority to the extent set forth in Section 8-511(b) and 8-511(c) of the UCC and (VI) if at any time DTC or other securities intermediary does not have sufficient Securities to satisfy claims of all of its entitlement holders with respect thereto then all holders will share pro rata in the Securities then held by DTC or such securities intermediary.

(vi) Absence of Manipulation. The Selling Shareholder has not taken, and will not take, directly or indirectly, any action which is designed to or which constituted or would be expected to cause or result in stabilization or manipulation of the price of any security of the Company to facilitate the sale or resale of the Securities.

(vii) Absence of Further Requirements. No filing with, or consent, approval, authorization, order, registration, qualification or decree of any arbitrator, court, governmental body, regulatory body, administrative agency or other authority, body or agency, domestic or foreign, is necessary or required for the performance by the Selling Shareholder of its obligations hereunder, or in connection with the sale and delivery of the Securities hereunder or the consummation of the transactions contemplated by this Agreement, except such as have been already obtained or as may be required under the 1933 Act, the 1933 Act Regulations, the rules of the NASDAQ Stock Market LLC, state securities laws or the rules of FINRA.

(viii) No Registration or Other Similar Rights. Other than the rights set forth in the Subscription and Registration Rights Agreement, dated as of November 8, 2012, by and among Prothena Corporation plc, Elan Corporation plc and Elan Science One Limited (the “Subscription Agreement”), the Selling Shareholder does not have any registration or other similar rights to have any equity or debt securities registered for sale by the Company under the Registration Statement or included in the offering contemplated by this Agreement.

(ix) No Free Writing Prospectuses. The Selling Shareholder has not prepared or had prepared on its behalf or used or referred to, any “free writing prospectus” (as defined in Rule 405), and has not distributed any written materials in connection with the offer or sale of the Securities.

(x) No Association with FINRA. Neither the Selling Shareholder nor any of its affiliates directly, or indirectly through one or more intermediaries, controls, or is controlled by, or is under common control with any member firm of FINRA or is a person associated with a member (within the meaning of the FINRA By-Laws) of FINRA.

(c) Officer’s Certificates. Any certificate signed by any officer of the Company or any of its subsidiaries delivered to the Representatives or to counsel for the Underwriters shall be deemed a representation and warranty by the Company to each Underwriter as to the matters covered thereby; and any certificate signed by or on behalf of the Selling Shareholder as such and delivered to the Representatives or to counsel for the Underwriters pursuant to the terms of this Agreement shall be deemed a representation and warranty by the Selling Shareholder to the Underwriters as to the matters covered thereby.

SECTION 2. Sale and Delivery to Underwriters; Closing.

(a) Initial Securities. On the basis of the representations and warranties herein contained and subject to the terms and conditions herein set forth, the Selling Shareholder agrees to sell to each Underwriter, severally and not jointly, and each Underwriter, severally and not jointly, agrees to purchase from the Selling Shareholder, at the price per share set forth in Schedule A, the number of Initial Securities set forth in Schedule A opposite the name of such Underwriter, plus any additional number of Initial Securities which such Underwriter may become obligated to purchase from the Selling Shareholder pursuant to the provisions of Section 10 hereof, subject to such adjustments among the Underwriters as ▇▇▇▇▇▇▇ ▇▇▇▇▇ and Citigroup in their sole discretion shall make to eliminate any purchases of fractional shares.

(b) Option Securities. In addition, on the basis of the representations and warranties herein contained and subject to the terms and conditions herein set forth, the Selling Shareholder hereby grants an option to the Underwriters, severally and not jointly, to purchase up to an additional 415,076 Ordinary Shares, as set forth in Schedule B, at the price per share set forth in Schedule A, less an amount per share equal to any dividends or distributions declared by the Company and payable on the Initial Securities but not payable on the Option Securities. The option hereby granted may be exercised for 30 days after the date hereof and may be exercised in whole or in part from time to time upon notice by the Representatives to the Selling Shareholder (with a copy to the Company) setting forth the number of Option Securities as

to which the several Underwriters are then exercising the option and the time and date of payment and delivery for such Option Securities. Any such time and date of delivery (a “Date of Delivery”) shall be determined by the Representatives, but shall not be later than seven full business days nor earlier than two full business days after the exercise of said option, nor in any event prior to the Closing Time; provided, however, that if the option is exercised prior to the delivery of the Initial Securities at the Closing Time, then the Date of Delivery may be no earlier than one full business day after the exercise of said option; provided further, that the Date of Delivery in such event is the same as the delivery of the Initial Securities at the Closing Time. If the option is exercised as to all or any portion of the Option Securities, each of the Underwriters, acting severally and not jointly, will purchase from the Selling Shareholder, that proportion of the total number of Option Securities then being purchased which the number of Initial Securities set forth in Schedule A opposite the name of such Underwriter bears to the total number of Initial Securities, subject, in each case, to such adjustments as ▇▇▇▇▇▇▇ ▇▇▇▇▇ and Citigroup in their sole discretion shall make to eliminate any sales or purchases of fractional shares.

(c) Payment. Payment of the purchase price for, and delivery of certificates for (if applicable), the Initial Securities shall be made at the offices of ▇▇▇▇▇▇ LLP, ▇▇▇▇ ▇▇▇▇▇▇▇ ▇▇▇▇▇▇, ▇▇▇▇ ▇▇▇▇, ▇▇▇▇▇▇▇▇▇▇, ▇▇▇▇▇, or at such other place as shall be agreed upon by the Representatives and the Company and the Selling Shareholder, at 9:00 A.M. (New York City time) on the third (fourth, if the pricing occurs after 4:30 P.M. (New York City time) on any given day) business day after the date hereof (unless postponed in accordance with the provisions of Section 10), or such other time not later than ten business days after such date as shall be agreed upon by the Representatives and the Company and the Selling Shareholder (such time and date of payment and delivery being herein called “Closing Time”). Delivery of the Initial Securities at the Closing Time shall be made through the facilities of The Depository Trust Company unless the Representatives shall otherwise instruct.

In addition, in the event that any or all of the Option Securities are purchased from the Selling Shareholder by the Underwriters, payment of the purchase price for, and delivery of certificates for (if applicable), such Option Securities shall be made at the above-mentioned offices, or at such other place as shall be agreed upon by the Representatives, the Company and the Selling Shareholder, on each Date of Delivery as specified in the notice from ▇▇▇▇▇▇▇ ▇▇▇▇▇ and Citigroup to the Company and the Selling Shareholder. Delivery of the Option Securities on each Date of Delivery shall be made through the facilities of The Depository Trust Company unless the Representatives shall otherwise instruct.

Payment to the Selling Shareholder shall be made by wire transfer of immediately available funds to bank accounts designated by the Selling Shareholder, against delivery to the Representatives for the respective accounts of the Underwriters of certificates or electronic book entries for the Securities to be purchased by them. It is understood that each Underwriter has authorized the Representatives, for its account, to: (i) accept delivery of, receipt for, and make payment of the purchase price for, the Initial Securities which it has agreed to purchase; and (ii) accept delivery of, receipt for, and make payment of the purchase price for the Option Securities, if any, for which it has agreed to purchase. ▇▇▇▇▇▇▇ ▇▇▇▇▇ or Citigroup, individually and not as representative of the Underwriters, may (but shall not be obligated to) make payment of the purchase price for the Initial Securities or the Option Securities, if any, to be purchased by any Underwriter whose funds have not been received by the Closing Time or the relevant Date of Delivery, as the case may be, but such payment shall not relieve such Underwriter from its obligations hereunder.

SECTION 3. Covenants of the Company and the Selling Shareholder. The Company and, solely with respect to paragraph (l) of this Section 3, the Selling Shareholder, covenant, severally and not jointly, with each Underwriter as follows:

(a) Compliance with Securities Regulations and Commission Requests. The Company, subject to Section 3(b), will comply with the requirements of Rule 430B, and will notify the Representatives as soon as practicable, and confirm the notice in writing, (i) when any post-effective amendment to the Registration Statement shall become effective or any amendment or supplement to the Prospectus shall have been filed, (ii) of the receipt of any comments from the Commission with respect to the Registration Statement or any amendment or supplement to the Prospectus, (iii) of any request by the Commission for any amendment to the Registration Statement or any amendment or supplement to the Prospectus, including any document incorporated by reference therein or for additional information, (iv) of the issuance by the Commission of any stop order suspending the effectiveness of the Registration Statement or any post-effective amendment or of any order preventing or suspending the use of any preliminary prospectus or the Prospectus, or of the suspension of the qualification of the Securities for offering or sale in any jurisdiction, or of the initiation or threatening of any proceedings for any of such purposes or of any examination pursuant to Section 8(d) or 8(e) of the 1933 Act concerning the Registration Statement and (v) if the Company becomes the subject of a proceeding under Section 8A of the 1933 Act in connection with the offering of the Securities. The Company will effect all filings required under Rule 424(b), in the manner and within the time period required by Rule 424(b) (without reliance on Rule 424(b)(8)), and will take such steps as it deems necessary to ascertain promptly whether the form of prospectus transmitted for filing under Rule 424(b) was received for filing by the Commission and, in the event that it was not, it will promptly file such prospectus. The Company will make every reasonable effort to prevent the issuance of any stop order, prevention or suspension and, if any such order is issued, to obtain the lifting thereof as soon as practicable.

(b) Continued Compliance with Securities Laws. The Company will comply with the 1933 Act, the 1933 Act Regulations, the 1934 Act and the 1934 Act Regulations so as to permit the completion of the distribution of the Securities as contemplated in this Agreement and in the Registration Statement, the General Disclosure Package and the Prospectus. If at any time when a prospectus relating to the Securities is (or, but for the exception afforded by Rule 172 of the 1933 Act Regulations (“Rule 172”), would be) required by the 1933 Act to be delivered in connection with sales of the Securities, any event shall occur or condition shall exist as a result of which it is necessary, in the opinion of counsel for the Underwriters or for the Company, to (i) amend the Registration Statement in order that the Registration Statement will not include an 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, (ii) amend or supplement the General Disclosure Package or the Prospectus in order that the General Disclosure Package or the Prospectus, as the case may be, will not include any untrue statement of a material fact or omit to state a material fact necessary in order to make the statements therein not misleading in the light of the circumstances existing at the time it is delivered to a purchaser or (iii) amend the Registration Statement or amend or supplement the General Disclosure Package or the Prospectus, as the case may be, in order to comply with the requirements of the 1933 Act or the 1933 Act Regulations, the Company will promptly (A) give the Representatives notice of such event, (B) prepare any amendment or supplement as may be necessary to correct such statement or omission or to make the Registration Statement, the General Disclosure Package or the Prospectus comply with such requirements and, a reasonable amount of time prior to any proposed filing or use, furnish the Representatives with copies of any such amendment or supplement and (C) file with the Commission any such amendment or supplement; provided that the Company shall not file or use any such amendment or supplement to which the Representatives or counsel for the Underwriters shall reasonably object. The Company will furnish to the Underwriters such number of copies of such amendment or supplement as the Underwriters may reasonably request. The Company has given the Representatives notice of any filings made pursuant to the 1934 Act or 1934 Act Regulations within 48 hours prior to the Applicable Time; the Company will give the Representatives notice of its intention to make any such filing from the Applicable Time to the Closing Time and will

furnish the Representatives with copies of any such documents a reasonable amount of time prior to such proposed filing, as the case may be, and will not file or use any such document to which the Representatives or counsel for the Underwriters shall reasonably object.

(c) Delivery of Registration Statements. The Company has furnished or will deliver to the Representatives and counsel for the Underwriters, without charge, signed copies of the Registration Statement as originally filed and each amendment thereto (including exhibits filed therewith or incorporated by reference therein and documents incorporated or deemed to be incorporated by reference therein) and signed copies of all consents and certificates of experts, and will also deliver to the Representatives, without charge, a conformed copy of the Registration Statement as originally filed and each amendment thereto (without exhibits) for each of the Underwriters. The copies of the Registration Statement and each amendment thereto furnished to the Underwriters will be identical to the electronically transmitted copies thereof filed with the Commission pursuant to ▇▇▇▇▇, except to the extent permitted by Regulation S-T.

(d) Delivery of Prospectuses. The Company has delivered to each Underwriter, without charge, as many copies of each preliminary prospectus as such Underwriter reasonably requested, and the Company hereby consents to the use of such copies for purposes permitted by the 1933 Act. The Company will furnish to each Underwriter, without charge, during the period when a prospectus relating to the Securities is (or, but for the exception afforded by Rule 172, would be) required to be delivered under the 1933 Act, such number of copies of the Prospectus (as amended or supplemented) as such Underwriter may reasonably request. The Prospectus and any amendments or supplements thereto furnished to the Underwriters will be identical to the electronically transmitted copies thereof filed with the Commission pursuant to ▇▇▇▇▇, except to the extent permitted by Regulation S-T.

(e) Blue Sky Qualifications. The Company will use its reasonable best efforts, in cooperation with the Underwriters and the Selling Shareholder, to qualify the Securities for sale by the Selling Shareholder, under the applicable securities laws of such states and other jurisdictions (domestic or foreign) as the Representatives may reasonably designate and to maintain such qualifications in effect so long as required to complete transfer of the Securities; provided, however, that neither the Company nor the Selling Shareholder shall be obligated to file any general consent to service of process or to qualify as a foreign corporation or as a dealer in securities in any jurisdiction in which it is not so qualified or to subject itself to taxation in respect of doing business in any jurisdiction in which it is not otherwise so subject.

(f) Rule 158. The Company will timely file such reports pursuant to the 1934 Act as are necessary in order to make generally available to its securityholders as soon as practicable an earnings statement for the purposes of, and to provide to the Underwriters the benefits contemplated by, the last paragraph of Section 11(a) of the 1933 Act.

(g) Listing. The Company will use its reasonable best efforts to maintain the listing of the Securities on The NASDAQ Global Select Market.

(h) Restriction on the Issue of Securities. During a period of 60 days from the date of the Prospectus, the Company will not, without the prior written consent of ▇▇▇▇▇▇▇ ▇▇▇▇▇ and Citigroup, (i) directly or indirectly, offer, pledge, issue, contract to issue, issue any option or contract to purchase, purchase any option or contract to sell, grant any option, right or warrant to purchase or otherwise transfer or dispose of any Ordinary Shares or any securities convertible into or exercisable or exchangeable for Ordinary Shares or file any registration statement under the 1933 Act with respect to any of the foregoing or (ii) enter into any swap or any other agreement or any transaction that transfers, in whole or in part,

directly or indirectly, the economic consequence of ownership of the Ordinary Shares, whether any such swap or transaction described in clause (i) or (ii) above is to be settled by delivery of Ordinary Shares or such other securities, in cash or otherwise. The foregoing sentence shall not apply to (A) the Securities to be issued by the Company hereunder, (B) any Ordinary Shares issued by the Company upon the exercise of an option outstanding on the date hereof and referred to in the Registration Statement, the General Disclosure Package and the Prospectus, or (C) any Ordinary Shares issued or options to subscribe for Ordinary Shares granted pursuant to existing employee benefit or equity incentive plans of the Company referred to in the Registration Statement, the General Disclosure Package and the Prospectus.

(i) Reporting Requirements. The Company, during the period when a Prospectus relating to the Securities is (or, but for the exception afforded by Rule 172, would be) required to be delivered under the 1933 Act, will file all documents required to be filed with the Commission pursuant to the 1934 Act within the time periods required by the 1934 Act and 1934 Act Regulations.

(j) Issuer Free Writing Prospectuses. Each of the Company and the Selling Shareholder agrees that, unless it obtains the prior written consent of the Representatives, it will not make any offer relating to the Securities that would constitute an Issuer Free Writing Prospectus or that would otherwise constitute a “free writing prospectus,” or a portion thereof, required to be filed by the Company with the Commission or retained by the Company under Rule 433; provided that the Representatives will be deemed to have consented to the Issuer Free Writing Prospectuses listed on Schedule C-2 hereto and any “road show that is a written communication” within the meaning of Rule 433(d)(8)(i) that has been reviewed by the Representatives. Each of the Company and the Selling Shareholder represents that it has treated or agrees that it will treat each such free writing prospectus consented to, or deemed consented to, by the Representatives as an “issuer free writing prospectus,” as defined in Rule 433, and that it has complied and will comply with the applicable requirements of Rule 433 with respect thereto, including timely filing with the Commission where required, legending and record keeping. If at any time following issuance of an Issuer Free Writing Prospectus there occurred or occurs an event or development as a result of which such Issuer Free Writing Prospectus conflicted or would conflict with the information contained in the Registration Statement, any preliminary prospectus or the Prospectus or included or would include an untrue statement of a material fact or omitted or would omit to state a material fact necessary in order to make the statements therein, in the light of the circumstances existing at that subsequent time, not misleading, the Company will promptly notify the Representatives and will promptly amend or supplement, at its own expense, such Issuer Free Writing Prospectus to eliminate or correct such conflict, untrue statement or omission.

SECTION 4. Payment of Expenses.

(a) Expenses of the Company. The Company will pay or cause to be paid all expenses incident to the performance of its obligations under this Agreement, including (i) the preparation, printing and filing of the Registration Statement (including financial statements and exhibits) as originally filed and each amendment thereto, (ii) the preparation, printing and delivery to the Underwriters of copies of each preliminary prospectus, each Issuer Free Writing Prospectus and the Prospectus and any amendments or supplements thereto, (iii) the preparation, issuance and delivery of the certificates or electronic book entries for the Securities to be sold by the Selling Shareholder to the Underwriters, including any share or other transfer taxes and any stamp or other duties payable upon the sale or delivery of the Securities to the Underwriters, (iv) the fees and disbursements of the Company’s counsel, accountants and other advisors, (v) the qualification of the Securities under securities laws in accordance with the provisions of Section 3(e) hereof, including filing fees and the reasonable fees and disbursements of counsel for the Underwriters not in excess of $5,000 in connection therewith and in connection with the preparation of the Blue Sky Survey and any supplement thereto, (vi) the fees and expenses of any

transfer agent or registrar for the Securities, (vii) the costs and expenses of the Company relating to investor presentations on any “road show” undertaken in connection with the marketing of the Securities, including without limitation, expenses associated with the production of road show slides and graphics, fees and expenses of any consultants engaged by the Company in connection with the road show presentations, travel and lodging expenses of the representatives and officers of the Company and any such consultants, and 50% of the cost of aircraft and other transportation chartered in connection with the road show, (viii) the filing fees incident to, and the reasonable fees and disbursements of counsel to the Underwriters in connection with, the review by FINRA of the terms of the sale by the Selling Shareholder, of the Securities, and (ix) the fees and expenses incurred in connection with the listing of the Securities on The NASDAQ Global Select Market.

(b) Expenses of the Selling Shareholder. The Selling Shareholder will pay all expenses incident to the performance of its obligations under this Agreement, including the preparation and issuance of electronic book-entries for the Securities to be sold by the Selling Shareholder to the Underwriters, including any share or other transfer taxes and any stamp and other duties and share and other transfer taxes, if any, payable upon the sale of the Securities to be sold by the Selling Shareholder to the Underwriters and their transfer between the Underwriters pursuant to an agreement between such Underwriters, and the fees and disbursements of its counsel and other advisors.

(c) Termination of Agreement. If this Agreement is terminated by the Representatives in accordance with the provisions of Section 5, Section 9(a)(i) or (iii), Section 10 or Section 11 hereof, the Company shall reimburse the Underwriters for all of their reasonable and documented out-of-pocket expenses, including the reasonable and documented fees and disbursements of counsel for the Underwriters; provided, however, that if this Agreement is terminated pursuant to Section 10, the Company shall only be required to reimburse the out of pocket expenses (including the reasonable fees and disbursements of counsel for the Underwriters) of, or attributable to, the Underwriters that have not failed to purchase the Securities that they have agreed to purchase hereunder.

(d) Allocation of Expenses. The provisions of this Section shall not affect any agreement that the Company and the Selling Shareholder has made or may make for the sharing of such costs and expenses, including as set forth in the Subscription Agreement.

SECTION 5. Conditions of Underwriters’ Obligations. The obligations of the several Underwriters hereunder are subject to the accuracy of the representations and warranties of the Company and the Selling Shareholder contained herein or in certificates of any officer of the Company or any of its subsidiaries or on behalf of the Selling Shareholder delivered pursuant to the provisions hereof, to the performance by the Company and the Selling Shareholder of their respective covenants and other obligations hereunder, and to the following further conditions:

(a) Effectiveness of Registration Statement. The Registration Statement, including any Rule 462(b) Registration Statement, has become effective and, at the Closing Time, no stop order suspending the effectiveness of the Registration Statement or any post-effective amendment thereto has been issued under the 1933 Act, no order preventing or suspending the use of any preliminary prospectus or the Prospectus has been issued and no proceedings for any of those purposes have been instituted or are pending or, to the Company’s knowledge, contemplated; and the Company has complied with each request (if any) from the Commission for additional information. The Company shall have paid the required Commission filing fees relating to the Securities in accordance with Rules 456(a) and 457(o) under the 1933 Act Regulations.

(b) Opinion of Counsel for Company. At the Closing Time, the Representatives shall have received the opinion and negative assurance letter, dated the Closing Time, of ▇▇▇▇▇▇ & ▇▇▇▇▇▇▇ LLP, counsel for the Company, in form and substance satisfactory to counsel for the Underwriters, together with signed or reproduced copies of such letter for each of the other Underwriters to the effect set forth in Exhibit A-1 hereto.

(c) Opinion of Intellectual Property Counsel for the Company. At the Closing Time, the Representatives shall have received the opinion, dated the Closing Time, of Cogent Law, intellectual property counsel for the Company, in form and substance satisfactory to counsel for the Underwriters, together with signed or reproduced copies of such letter for each of the other Underwriters to the effect set forth in Exhibit A-2 hereto.

(d) Opinion of Intellectual Property Counsel for the Company. At the Closing Time, the Representatives shall have received the opinion, dated the Closing Time, of ▇▇▇▇▇▇ ▇▇▇▇▇▇▇ ▇▇▇▇▇▇▇▇▇ & ▇▇▇▇ LLP, intellectual property counsel for the Company, in form and substance satisfactory to counsel for the Underwriters, together with signed or reproduced copies of such letter for each of the other Underwriters to the effect set forth in Exhibit A-3 hereto.

(e) Opinion of Intellectual Property Counsel for the Company. At the Closing Time, the Representatives shall have received the opinion, dated the Closing Time, of ▇▇▇▇▇▇ & Bird LLP, intellectual property counsel for the Company, in form and substance satisfactory to counsel for the Underwriters, together with signed or reproduced copies of such letter for each of the other Underwriters to the effect set forth in Exhibit A-4 hereto.

(f) Opinion of Irish Counsel to the Company. At the Closing Time, the Representatives shall have received the opinion, dated the Closing Time, of A&L Goodbody, Irish counsel for the Company, in form and substance satisfactory to counsel for the Underwriters, together with signed or reproduced copies of such letter for each of the other Underwriters to the effect set forth in Exhibit A-5 hereto.

(g) Opinion of Counsel for the Selling Shareholder. At the Closing Time, the Representatives shall have received the opinion, dated the Closing Time, of Cadwalader, ▇▇▇▇▇▇▇▇▇▇ & ▇▇▇▇ LLP, counsel for the Selling Shareholder, in substantially the form attached hereto as Exhibit B-1, together with signed or reproduced copies of such letter for each of the other Underwriters.

(h) Opinion of Irish Counsel for the Selling Shareholder. At the Closing Time, the Representatives shall have received the opinion, dated the Closing Time, of ▇▇▇▇▇▇ ▇▇▇▇▇▇▇, Irish counsel for the Selling Shareholder, in substantially the form attached hereto as Exhibit B-2, together with signed or reproduced copies of such letter for each of the other Underwriters.

(i) Opinion of Counsel for Underwriters. At the Closing Time, the Representatives shall have received the opinion, together with a negative assurance letter, each dated the Closing Time, of ▇▇▇▇▇▇ LLP, counsel for the Underwriters, together with signed or reproduced copies of such letters for each of the other Underwriters substantially in the forms set forth attached hereto as Exhibit A-6. In giving such opinion and negative assurance letter, such counsel may rely, as to all matters governed by the laws of jurisdictions other than the law of the State of New York, the General Corporation Law of the State of Delaware and the federal securities laws of the United States, upon the opinions of counsel satisfactory to the Representatives. Such counsel may also state that, insofar as such opinion and negative assurance letter involve factual matters, they have relied, to the extent they deem proper, upon certificates of officers and other representatives of the Company and its subsidiaries and certificates of public officials.

(j) Officers’ Certificate. At the Closing Time, there shall not have been, since the date hereof or since the respective dates as of which information is given in the Registration Statement, the General Disclosure Package or the Prospectus, any Material Adverse Effect, and the Representatives shall have received a certificate of the Chief Executive Officer or a Vice President of the Company and of the chief financial or chief accounting officer of the Company, dated the Closing Time, to the effect that (i) there has been no such Material Adverse Effect, (ii) the representations and warranties of the Company in this Agreement are true and correct with the same force and effect as though expressly made at and as of the Closing Time, (iii) the Company has complied with all agreements and satisfied all conditions on its part to be performed or satisfied at or prior to the Closing Time, and (iv) no stop order suspending the effectiveness of the Registration Statement under the 1933 Act has been issued, no order preventing or suspending the use of any preliminary prospectus or the Prospectus has been issued and no proceedings for any of those purposes have been instituted or are pending or, to their knowledge, contemplated.

(k) Certificate of Selling Shareholder. At the Closing Time, the Representatives shall have received a certificate of the Selling Shareholder, dated the Closing Time, to the effect that (i) the representations and warranties of the Selling Shareholder in this Agreement are true and correct with the same force and effect as though expressly made at and as of the Closing Time and (ii) the Selling Shareholder has complied with all agreements and all conditions on its part to be performed under this Agreement at or prior to the Closing Time.

(l) Accountant’s Comfort Letter. At the time of the execution of this Agreement, the Representatives shall have received from KPMG LLP a letter, dated such date, in form and substance satisfactory to the Representatives, together with signed or reproduced copies of such letter for each of the other Underwriters 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 in the Registration Statement, the General Disclosure Package and the Prospectus.

(m) Bring-down Comfort Letter. At the Closing Time, the Representatives shall have received from KPMG LLP a letter, dated as of the Closing Time, to the effect that they reaffirm the statements made in the letter furnished pursuant to subsection (l) of this Section, except that the specified date referred to shall be a date not more than three business days prior to the Closing Time.

(n) Approval of Listing. At the Closing Time, the Securities shall have been approved for listing on The NASDAQ Global Select Market, subject only to official notice of issuance.

(o) No Objection. FINRA has confirmed that it has not raised any objection with respect to the fairness and reasonableness of the underwriting terms and arrangements relating to the offering of the Securities.

(p) Lock-up Agreements. At the date of this Agreement, the Representatives shall have received an agreement substantially in the form of Exhibit C hereto signed by the persons listed on Schedule D hereto.

(q) Conditions to Purchase the Option Securities. In the event that the Underwriters exercise their option provided in Section 2(b) hereof to purchase from the Selling Shareholder all or any portion of the Option Securities, the representations and warranties of the Company contained herein and the statements in any certificates furnished by the Company, any of its subsidiaries hereunder shall be true and correct as of each Date of Delivery and, at the relevant Date of Delivery, the Representatives shall have received:

(i) Officers’ Certificate. A certificate, dated such Date of Delivery, of the Chief Executive Officer or a Vice President of the Company and of the chief financial or chief accounting officer of the Company confirming that the certificate delivered at the Closing Time pursuant to Section 5(j) hereof remains true and correct as of such Date of Delivery.

(ii) Certificate of the Selling Shareholder. A certificate, dated such Date of Delivery, of the Selling Shareholder confirming that the certificate delivered at the Closing Time pursuant to Section 5(k) remains true and correct as of such Date of Delivery.

(iii) Opinion of Counsel for Company. If requested by the Representatives, the opinion of ▇▇▇▇▇▇ & ▇▇▇▇▇▇▇ LLP, counsel for the Company, in form and substance satisfactory to counsel for the Underwriters, dated such Date of Delivery, relating to the Option Securities to be purchased on such Date of Delivery and otherwise to the same effect as the opinion required by Section 5(b) hereof.

(iv) Opinion of Intellectual Property Counsel for the Company. If requested by the Representatives, the opinion of Cogent Law, intellectual property counsel for the Company, in form and substance satisfactory to counsel for the Underwriters, dated such Date of Delivery, relating to the Option Securities to be purchased on such Date of Delivery and otherwise to the same effect as the opinion required by Section 5(c) hereof.

(v) Opinion of Intellectual Property Counsel for the Company. If requested by the Representatives, the opinion of ▇▇▇▇▇▇ ▇▇▇▇▇▇▇ ▇▇▇▇▇▇▇▇▇ & ▇▇▇▇ LLP, intellectual property counsel for the Company, in form and substance satisfactory to counsel for the Underwriters, dated such Date of Delivery, relating to the Option Securities to be purchased on such Date of Delivery and otherwise to the same effect as the opinion required by Section 5(d) hereof.

(vi) Opinion of Intellectual Property Counsel for the Company. If requested by the Representatives, the opinion of ▇▇▇▇▇▇ & Bird LLP, intellectual property counsel for the Company, in form and substance satisfactory to counsel for the Underwriters, dated such Date of Delivery, relating to the Option Securities to be purchased on such Date of Delivery and otherwise to the same effect as the opinion required by Section 5(e) hereof.

(vii) Opinion of Irish Counsel for the Company. If requested by the Representatives, the opinion of A&L Goodbody, Irish counsel for the Company, in form and substance satisfactory to counsel for the Underwriters, dated such Date of Delivery, relating to the Option Securities to be purchased on such Date of Delivery and otherwise to the same effect as the opinion required by Section 5(f) hereof.

(viii) Opinion of Counsel for the Selling Shareholder. If requested by the Representatives, the opinion of Cadwalader, ▇▇▇▇▇▇▇▇▇▇ & ▇▇▇▇ LLP, counsel for the Selling Shareholder, in form and substance satisfactory to counsel for the Underwriters, dated such Date of Delivery, relating to the Option Securities to be purchased on such Date of Delivery and otherwise to the same effect as the opinion required by Section 5(g) hereof.

(ix) Opinion of Irish Counsel for the Selling Shareholder. If requested by the Representatives, the opinion of ▇▇▇▇▇▇ ▇▇▇▇▇▇▇, Irish counsel for the Selling Shareholder, in form and substance satisfactory to counsel for the Underwriters, dated such Date of Delivery, relating to the Option Securities to be purchased on such Date of Delivery and otherwise to the same effect as the opinion required by Section 5(h) hereof.

(x) Opinion of Counsel for Underwriters. If requested by the Representatives, the opinion and negative assurance letter of ▇▇▇▇▇▇ LLP, counsel for the Underwriters, dated such Date of Delivery, relating to the Option Securities to be purchased on such Date of Delivery and otherwise to the same effect as the opinion required by Section 5(i) hereof.

(xi) Bring-down Comfort Letter. If requested by the Representatives, a letter from KPMG LLP, in form and substance satisfactory to the Representatives and dated such Date of Delivery, substantially in the same form and substance as the letter furnished to the Representatives pursuant to Section 5(m) hereof, except that the “specified date” in the letter furnished pursuant to this paragraph shall be a date not more than three business days prior to such Date of Delivery.

(r) Additional Documents. At the Closing Time and at each Date of Delivery (if any) counsel for the Underwriters shall have been furnished with such documents and opinions as they may reasonably require for the purpose of enabling them to pass upon the issuance and sale of the Securities as herein contemplated, or in order to evidence the accuracy of any of the representations or warranties, or the fulfillment of any of the conditions, herein contained; and all proceedings taken by the Company and the Selling Shareholder in connection with the issuance and sale of the Securities as herein contemplated shall be reasonably satisfactory in form and substance to the Representatives and counsel for the Underwriters.

(s) Termination of Agreement. If any condition specified in this Section shall not have been fulfilled when and as required to be fulfilled, this Agreement, or, in the case of any condition to the purchase of Option Securities on a Date of Delivery which is after the Closing Time, the obligations of the several Underwriters to purchase the relevant Option Securities, may be terminated by the Representatives by notice to the Company and the Selling Shareholder at any time at or prior to Closing Time or such Date of Delivery, as the case may be, and such termination shall be without liability of any party to any other party except as provided in Section 4 and except that Sections 1, 6, 7, 8, 15, 16 and 17 shall survive any such termination and remain in full force and effect.

SECTION 6. Indemnification.

(a) Indemnification of Underwriters. The Company agrees to indemnify and hold harmless each Underwriter, its affiliates (as such term is defined in Rule 501(b) under the 1933 Act (each, an “Affiliate”)), its selling agents and each person, if any, who controls any Underwriter within the meaning of Section 15 of the 1933 Act or Section 20 of the 1934 Act as follows:

(i) against any and all loss, liability, claim, damage and expense whatsoever, as incurred, arising out of any untrue statement or alleged untrue statement of a material fact contained in the Registration Statement (or any amendment thereto), including any information deemed to be a party thereof pursuant to Rule 430B, or the omission or alleged omission therefrom of a material fact required to be stated therein or necessary to make the statements therein not misleading or arising out of any untrue statement or

alleged untrue statement of a material fact included (A) in any preliminary prospectus, any Issuer Free Writing Prospectus, the General Disclosure Package or the Prospectus (or any amendment or supplement thereto), or (B) in any materials or information provided to investors by, or with the approval of, the Company in connection with the marketing of the offering of the Securities (“Marketing Materials”), including any roadshow or investor presentations made to investors by the Company (whether in person or electronically), or the omission or alleged omission in any preliminary prospectus, Issuer Free Writing Prospectus, Prospectus or in any Marketing Materials of a material fact necessary in order to make the statements therein, in the light of the circumstances under which they were made, not misleading;

(ii) against any and all loss, liability, claim, damage and expense whatsoever, as incurred, to the extent of the aggregate amount paid in settlement of any litigation, or any investigation or proceeding by any governmental agency or body, commenced or threatened, or of any claim whatsoever based upon any such untrue statement or omission, or any such alleged untrue statement or omission; provided that (subject to Section 6(e) below) any such settlement is effected with the written consent of the Company;

(iii) against any and all documented expense whatsoever, as incurred (including the fees and disbursements of one counsel (in addition to local counsel) chosen by ▇▇▇▇▇▇▇ ▇▇▇▇▇ and Citigroup), reasonably incurred in investigating, preparing or defending against any litigation, or any investigation or proceeding by any governmental agency or body, commenced or threatened, or any claim whatsoever based upon any such untrue statement or omission, or any such alleged untrue statement or omission, to the extent that any such expense is not paid under (i) or (ii) above;

provided, however, that this indemnity agreement shall not apply to any loss, liability, claim, damage or expense to the extent arising out of any untrue statement or omission or alleged untrue statement or omission made in the Registration Statement (or any amendment thereto), including any information deemed to be a part thereof pursuant to Rule 430B, the General Disclosure Package or the Prospectus (or any amendment or supplement thereto) in reliance upon and in conformity with the Underwriter Information.

(b) Indemnification of Underwriters by Selling Shareholder. The Selling Shareholder agrees to indemnify and hold harmless each Underwriter, its Affiliates and selling agents and each person, if any, who controls any Underwriter within the meaning of Section 15 of the 1933 Act or Section 20 of the 1934 Act to the extent and in the manner set forth in clauses (a)(i), (ii) and (iii) above ; provided that the Selling Shareholder shall be liable only to the extent that such untrue statement or alleged untrue statement or omission or alleged omission has been made in the Registration Statement, any preliminary prospectus, the General Disclosure Package, the Prospectus (or any amendment or supplement thereto) or any Issuer Free Writing Prospectus in reliance upon and in conformity with the Selling Shareholder Information; provided, further, that any loss, liability, claim, damage or expense under this subsection of the Selling Shareholder shall be limited to an amount equal to the aggregate gross proceeds after underwriting commissions and discounts, but before expenses, to the Selling Shareholder from the sale of Securities sold by the Selling Shareholder hereunder.

(c) Indemnification of Company, Directors and Officers and Selling Shareholder. Each Underwriter severally agrees to indemnify and hold harmless the Company, its directors, each of its officers who signed the Registration Statement, and each person, if any, who controls the Company

within the meaning of Section 15 of the 1933 Act or Section 20 of the 1934 Act, and the Selling Shareholder against any and all loss, liability, claim, damage and expense described in the indemnity contained in subsection (a) of this Section, as incurred, but only with respect to untrue statements or omissions, or alleged untrue statements or omissions, made in the Registration Statement (or any amendment thereto), including any information deemed to be a part thereof pursuant to Rule 430B, the General Disclosure Package or the Prospectus (or any amendment or supplement thereto) in reliance upon and in conformity with the Underwriter Information.

(d) Actions against Parties; Notification. Each indemnified party shall give notice as promptly as reasonably practicable to each indemnifying party of any action commenced against it in respect of which indemnity may be sought hereunder, but failure to so notify an indemnifying party shall not relieve such indemnifying party from any liability hereunder to the extent it is not materially prejudiced as a result thereof and in any event shall not relieve it from any liability which it may have otherwise than on account of this indemnity agreement. In the case of parties indemnified pursuant to Section 6(a) and 6(b) above, counsel to the indemnified parties shall be selected by ▇▇▇▇▇▇▇ ▇▇▇▇▇ and Citigroup, and, in the case of parties indemnified pursuant to Section 6(c) above, counsel to the indemnified parties shall be selected by the Company. An indemnifying party may participate at its own expense in the defense of any such action; provided, however, that counsel to the indemnifying party shall not (except with the consent of the indemnified party) also be counsel to the indemnified party. In no event shall the indemnifying parties be liable for fees and expenses of more than one counsel (in addition to any local counsel) separate from their own counsel for all indemnified parties in connection with any one action or separate but similar or related actions in the same jurisdiction arising out of the same general allegations or circumstances. No indemnifying party shall, without the prior written consent of the indemnified parties, settle or compromise or consent to the entry of any judgment with respect to any litigation, or any investigation or proceeding by any governmental agency or body, commenced or threatened, or any claim whatsoever in respect of which indemnification or contribution could be sought under this Section 6 or Section 7 hereof (whether or not the indemnified parties are actual or potential parties thereto), unless such settlement, compromise or consent (i) includes an unconditional release of each indemnified party from all liability arising out of such litigation, investigation, proceeding or claim and (ii) does not include a statement as to or an admission of fault, culpability or a failure to act by or on behalf of any indemnified party.

(e) Settlement without Consent if Failure to Reimburse. 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 in this Section 6, such indemnifying party agrees that it shall be liable for any settlement of the nature contemplated by Section 6(a)(ii) effected without its written consent if (i) suchsettlement is entered into more than 60 days after receipt by such indemnifying party of the aforesaid request, (ii) such indemnifying party shall have received notice of the terms of such settlement at least 30 days prior to such settlement being entered into and (iii) such indemnifying party shall not have reimbursed such indemnified party in accordance with such request prior to the date of such settlement.

SECTION 7. Contribution. If the indemnification provided for in Section 6 hereof is for any reason unavailable to or insufficient to hold harmless an indemnified party in respect of any losses, liabilities, claims, damages or expenses referred to therein, then each indemnifying party shall contribute to the aggregate amount of such losses, liabilities, claims, damages and expenses incurred by such indemnified party, as incurred, (i) in such proportion as is appropriate to reflect the relative benefits received by the Company and the Selling Shareholder, on the one hand, and the Underwriters, on the other hand, from the offering of the Securities pursuant to this Agreement or (ii) if the allocation provided by clause (i) is not permitted by applicable law, in such proportion as is appropriate to reflect not only the

relative benefits referred to in clause (i) above but also the relative fault of the Company and the Selling Shareholder, on the one hand, and of the Underwriters, on the other hand, in connection with the statements or omissions which resulted in such losses, liabilities, claims, damages or expenses, as well as any other relevant equitable considerations.

The relative benefits received by the Company and the Selling Shareholder, on the one hand, and the Underwriters, on the other hand, in connection with the offering of the Securities pursuant to this Agreement shall be deemed to be in the same respective proportions as the total net proceeds from the offering of the Securities pursuant to this Agreement (before deducting expenses) received by the Company and the Selling Shareholder, on the one hand, and the total underwriting discount received by the Underwriters, on the other hand, in each case as set forth on the cover of the Prospectus, bear to the aggregate initial public offering price of the Securities as set forth on the cover of the Prospectus.

The relative fault of the Company and the Selling Shareholder, on the one hand, and the Underwriters, on the other hand, shall be determined by reference to, among other things, whether any such untrue or alleged untrue statement of a material fact or omission or alleged omission to state a material fact relates to information supplied by the Company, Selling Shareholder Information or information supplied by the Underwriters and the parties’ relative intent, knowledge, access to information and opportunity to correct or prevent such statement or omission.

The Company, the Selling Shareholder and the Underwriters agree that it would not be just and equitable if contribution pursuant to this Section 7 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 which does not take account of the equitable considerations referred to above in this Section 7. The aggregate amount of losses, liabilities, claims, damages and expenses incurred by an indemnified party and referred to above in this Section 7 shall be deemed to include any legal or other expenses reasonably incurred by such indemnified party in investigating, preparing or defending against any litigation, or any investigation or proceeding by any governmental agency or body, commenced or threatened, or any claim whatsoever based upon any such untrue or alleged untrue statement or omission or alleged omission.

Notwithstanding the provisions of this Section 7, no Underwriter shall be required to contribute any amount in excess of the underwriting discounts and commissions received by such Underwriter in connection with the Securities underwritten by it and distributed to the public.

Additionally, notwithstanding the provisions of this Section 7, the Selling Shareholder shall not be required to contribute any amount in excess of the aggregate gross proceeds after underwriting commissions and discounts, but before expenses, to the Selling Shareholder from the sale of Securities sold by the Selling Shareholder hereunder.

No person guilty of fraudulent misrepresentation (within the meaning of Section 11(f) of the ▇▇▇▇ ▇▇▇) shall be entitled to contribution from any person who was not guilty of such fraudulent misrepresentation.

For purposes of this Section 7, each person, if any, who controls an Underwriter within the meaning of Section 15 of the 1933 Act or Section 20 of the 1934 Act and each Underwriter’s Affiliates and selling agents shall have the same rights to contribution as such Underwriter, and each director of the Company, each officer of the Company who signed the Registration Statement, and each person, if any, who controls the Company or the Selling Shareholder within the meaning of Section 15 of the 1933 Act or Section 20 of the 1934 Act shall have the same rights to contribution as the Company or the Selling Shareholder, as the case may be. The Underwriters’ respective obligations to contribute pursuant to this Section 7 are several in proportion to the number of Initial Securities set forth opposite their respective names in Schedule A hereto and not joint.

The provisions of this Section shall not affect any agreement among the Company and the Selling Shareholder with respect to contribution.

SECTION 8. Representations, Warranties and Agreements to Survive. All representations, warranties and agreements contained in this Agreement or in certificates of officers of the Company or any of its subsidiaries or the Selling Shareholder submitted pursuant hereto, shall remain operative and in full force and effect regardless of (i) any investigation made by or on behalf of any Underwriter or its Affiliates or selling agents, any person controlling any Underwriter, its officers or directors, any person controlling the Company or any person controlling the Selling Shareholder and (ii) delivery of and payment for the Securities.

SECTION 9. Termination of Agreement.

(a) Termination. The Representatives may terminate this Agreement, by notice to the Company and the Selling Shareholder, at any time at or prior to the Closing Time (i) if there has been, in the judgment of the Representatives, since the time of execution of this Agreement or since the respective dates as of which information is given in the Registration Statement, the General Disclosure Package or the Prospectus, any Material Adverse Effect, or (ii) if there has occurred any material adverse change in the financial markets in the United States or the international financial markets, any outbreak of hostilities or escalation thereof or other calamity or crisis or any change or development involving a prospective change in national or international political, financial or economic conditions, in each case the effect of which is such as to make it, in the judgment of the Representatives, impracticable or inadvisable to proceed with the completion of the offering or to enforce contracts for the sale of the Securities, or (iii) if trading in any securities of the Company has been suspended or materially limited by the Commission or The NASDAQ Global Select Market, or (iv) if trading generally on the New York Stock Exchange or in The NASDAQ Global Select Market has been suspended or materially limited, or minimum or maximum prices for trading have been fixed, or maximum ranges for prices have been required, by any of said exchanges or by order of the Commission, FINRA or any other governmental authority, or (v) a material disruption has occurred in commercial banking or securities settlement or clearance services in the United States or with respect to Clearstream or Euroclear systems in Europe, or (vi) if a banking moratorium has been declared by either Federal or New York authorities.

(b) Liabilities. If this Agreement is terminated pursuant to this Section, such termination shall be without liability of any party to any other party except as provided in Section 4 hereof, and provided further that Sections 1, 4, 6, 7, 8, 15, 16 and 17 shall survive such termination and remain in full force and effect.

SECTION 10. Default by One or More of the Underwriters. If one or more of the Underwriters shall fail at the Closing Time or a Date of Delivery to purchase from the Selling Shareholder the Securities which it or they are obligated to purchase under this Agreement (the “Defaulted Securities”), the Representatives shall make arrangements for one or more of the non-defaulting Underwriters, or any other underwriters, to purchase all, but not less than all, of the Defaulted Securities in such amounts as may be agreed upon and upon the terms herein set forth; if, however, the Representatives shall not have completed such arrangements within such 24-hour period, then:

(i) if the number of Defaulted Securities does not exceed 10% of the number of Securities to be sold by the Selling Shareholder on such date, each of the non-defaulting Underwriters shall be obligated, severally and not jointly, to purchase the full amount thereof in the proportions that their respective underwriting obligations hereunder bear to the underwriting obligations of all non-defaulting Underwriters, or

(ii) if the number of Defaulted Securities exceeds 10% of the number of Securities to be sold by the Selling Shareholder on such date, this Agreement or, with respect to any Date of Delivery which occurs after the Closing Time, the obligation of the Underwriters to purchase, or the Selling Shareholder to sell, the Option Securities to be sold on such Date of Delivery shall terminate without liability on the part of any non-defaulting Underwriter.

No action taken pursuant to this Section shall relieve any defaulting Underwriter from liability in respect of its default.

In the event of any such default which does not result in a termination of this Agreement or, in the case of a Date of Delivery which is after the Closing Time, which does not result in a termination of the obligation of the Underwriters to purchase from the Selling Shareholder, and the Selling Shareholder to sell, the relevant Option Securities, as the case may be, either the (i) Representatives or (ii) the Company and the Selling Shareholder shall have the right to postpone Closing Time or the relevant Date of Delivery, as the case may be, for a period not exceeding seven days in order to effect any required changes in the Registration Statement, the General Disclosure Package or the Prospectus or in any other documents or arrangements. As used herein, the term “Underwriter” includes any person substituted for an Underwriter under this Section 10.

SECTION 11. Default by the Selling Shareholder or the Company.

(a) If the Selling Shareholder shall fail at the Closing Time to sell and deliver the number of Securities which the Selling Shareholder is obligated to sell hereunder, then the Underwriters may, at the option of the Representatives, by notice from the Representatives to the Company, terminate this Agreement without any liability on the fault of any non-defaulting party except that the provisions of Sections 1, 4, 6, 7, 8, 15, 16 and 17 shall remain in full force and effect. No action taken pursuant to this Section 11 shall relieve the Selling Shareholder so defaulting from liability, if any, in respect of such default.

(b) In the event of a default by the Selling Shareholder as referred to in this Section 11, each of the Representatives and the Company shall have the right to postpone the Closing Time for a period not exceeding seven days in order to effect any required change in the Registration Statement, the General Disclosure Package or the Prospectus or in any other documents or arrangements.

SECTION 12. Notices. All notices and other communications hereunder shall be in writing and shall be deemed to have been duly given if mailed or transmitted by any standard form of telecommunication. Notices to the Underwriters shall be directed to ▇▇▇▇▇▇▇ ▇▇▇▇▇ at ▇▇▇ ▇▇▇▇▇▇ ▇▇▇▇, ▇▇▇ ▇▇▇▇, ▇▇▇ ▇▇▇▇ ▇▇▇▇▇, attention of Syndicate Department (facsimile: (▇▇▇) ▇▇▇-▇▇▇▇), with a copy to ECM Legal (facsimile: (▇▇▇) ▇▇▇-▇▇▇▇), and to Citigroup at ▇▇▇ ▇▇▇▇▇▇▇▇▇ ▇▇▇▇▇▇, ▇▇▇ ▇▇▇▇, ▇▇▇ ▇▇▇▇ ▇▇▇▇▇, attention ▇▇▇▇ Arvanistis (phone: ▇▇▇-▇▇▇-▇▇▇▇) ; notices to the Company shall be directed to it at:

Prothena Corporation plc

▇▇-▇▇ ▇▇▇▇▇ ▇▇▇▇ ▇▇▇▇

▇▇▇▇▇▇ ▇, ▇▇▇▇▇▇▇

Attention: Secretary

with copies to:

Prothena Biosciences Inc

▇▇▇ ▇▇▇▇▇▇▇ ▇▇▇▇▇▇▇▇▇

▇▇▇▇▇ ▇▇▇ ▇▇▇▇▇▇▇▇▇, ▇▇ ▇▇▇▇▇, ▇.▇.▇.

Attention: ▇▇▇▇ ▇▇▇▇▇▇, CFO

▇▇▇▇▇▇ & ▇▇▇▇▇▇▇ LLP

▇▇▇ ▇▇▇▇▇ ▇▇▇▇▇

▇▇▇▇▇ ▇▇▇▇, ▇▇ ▇▇▇▇▇, ▇.▇.▇.

Attention: ▇▇▇▇ ▇. ▇▇▇▇▇▇▇▇▇

▇▇▇▇▇▇ ▇. ▇▇▇▇▇▇▇▇

and notices to the Selling Shareholder shall be directed to:


				Elan Science One Limited c/▇ ▇▇▇▇▇▇▇ Company plc ▇▇▇▇▇▇▇▇ ▇▇▇▇▇▇▇▇, ▇▇▇▇▇ ▇▇▇▇▇ ▇▇▇▇▇ ▇▇., ▇▇▇▇▇▇ ▇, ▇▇▇▇▇▇▇ Attention: ▇▇▇▇ ▇▇▇▇▇▇

		with a copy to:		Cadwalader, ▇▇▇▇▇▇▇▇▇▇ & ▇▇▇▇ LLP ▇▇▇ ▇▇▇▇▇ ▇▇▇▇▇▇▇▇▇ ▇▇▇▇▇▇ ▇▇▇ ▇▇▇▇, ▇▇ ▇▇▇▇▇, U.S.A. Attention: ▇▇▇▇▇▇▇ ▇. ▇▇▇▇▇ ▇▇▇▇▇▇▇ ▇. ▇▇▇▇▇

SECTION 13. No Advisory or Fiduciary Relationship. Each of the Company and the Selling Shareholder acknowledges and agrees that (a) the sale of the Securities pursuant to this Agreement, including the determination of the initial public offering price of the Securities and any related discounts and commissions, is an arm’s-length commercial transaction between the Company and the Selling Shareholder, on the one hand, and the several Underwriters, on the other hand, (b) in connection with the offering of the Securities and the process leading thereto, each Underwriter is and has been acting solely as a principal and is not the agent or fiduciary of the Company, any of its subsidiaries or the Selling Shareholder, or its respective shareholders, creditors, employees or any other party, (c) no Underwriter has assumed or will assume an advisory or fiduciary responsibility in favor of the Company or Selling Shareholder with respect to the offering of the Securities or the process leading thereto (irrespective of whether such Underwriter has advised or is currently advising the Company, any of its subsidiaries or Selling Shareholder on other matters) and no Underwriter has any obligation to the Company or Selling Shareholder with respect to the offering of the Securities except the obligations expressly set forth in this Agreement, (d) the Underwriters and their respective affiliates may be engaged in a broad range of transactions that involve interests that differ from those of each of the Company and the Selling Shareholder, and (e) the Underwriters have not provided any legal, accounting, regulatory or tax advice with respect to the offering of the Securities and the Company and the Selling Shareholder has consulted its own respective legal, accounting, regulatory and tax advisors to the extent it deemed appropriate.

SECTION 14. Parties. This Agreement shall each inure to the benefit of and be binding upon the Underwriters, the Company and the Selling Shareholder and their respective successors. Nothing expressed or mentioned in this Agreement is intended or shall be construed to give any person, firm or corporation, other than the Underwriters, the Company and the Selling Shareholder and their respective successors and the controlling persons and officers and directors referred to in Sections 6 and 7 and their heirs and legal representatives, any legal or equitable right, remedy or claim under or in respect of this Agreement or any provision herein contained. This Agreement and all conditions and provisions hereof are intended to be for the sole and exclusive benefit of the Underwriters, the Company and the Selling Shareholder and their respective successors, and said controlling persons and officers and directors and their heirs and legal representatives, and for the benefit of no other person, firm or corporation. No purchaser of Securities from any Underwriter shall be deemed to be a successor by reason merely of such purchase.

SECTION 15. Trial by Jury. The Company (on its behalf and, to the extent permitted by applicable law, on behalf of its shareholders and affiliates), the Selling Shareholder and each of the Underwriters 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.

SECTION 16. GOVERNING LAW. THIS AGREEMENT AND ANY CLAIM, CONTROVERSY OR DISPUTE ARISING UNDER OR RELATED TO THIS AGREEMENT SHALL BE GOVERNED BY, AND CONSTRUED IN ACCORDANCE WITH THE LAWS OF, THE STATE OF NEW YORK WITHOUT REGARD TO ITS CHOICE OF LAW PROVISIONS.

SECTION 17. Consent to Jurisdiction; Waiver of Immunity. Any legal suit, action or proceeding arising out of or based upon this Agreement or the transactions contemplated hereby (“Related Proceedings”) shall be instituted in (i) the federal courts of the United States of America located in the City and County of New York, Borough of Manhattan or (ii) the courts of the State of New York located in the City and County of New York, Borough of Manhattan (collectively, the “Specified Courts”), and each party irrevocably submits to the exclusive jurisdiction (except for proceedings instituted in regard to the enforcement of a judgment of any such court (a “Related Judgment”), as to which such jurisdiction is non-exclusive) of such courts in any such suit, action or proceeding. Service of any process, summons, notice or document by mail to such party’s address set forth above shall be effective service of process for any suit, action or other proceeding brought in any such court. The parties irrevocably and unconditionally waive any objection to the laying of venue of any suit, action or other proceeding in the Specified Courts and irrevocably and unconditionally waive and agree not to plead or claim in any such court that any such suit, action or other proceeding brought in any such court has been brought in an inconvenient forum. Each party not located in the United States consents to receive service of process or other legal summons for purposes of any such suit, action or proceeding that may be instituted in any state or federal court in the City and County of New York. With respect to any Related Proceeding, each party irrevocably waives, to the fullest extent permitted by applicable law, all immunity (whether on the basis of sovereignty or otherwise) from jurisdiction, service of process, attachment (both before and after judgment) and execution to which it might otherwise be entitled in the Specified Courts, and with respect to any Related Judgment, each party waives any such immunity in the Specified Courts or any other court of competent jurisdiction, and will not raise or claim or cause to be pleaded any such immunity at or in respect of any such Related Proceeding or Related Judgment, including, without limitation, any immunity pursuant to the United States Foreign Sovereign Immunities Act of 1976, as amended.

SECTION 18. TIME. TIME SHALL BE OF THE ESSENCE OF THIS AGREEMENT. EXCEPT AS OTHERWISE SET FORTH HEREIN, SPECIFIED TIMES OF DAY REFER TO NEW YORK CITY TIME.

SECTION 19. Counterparts. This Agreement may be executed in any number of counterparts, each of which shall be deemed to be an original, but all such counterparts shall together constitute one and the same Agreement.

SECTION 20. Effect of Headings. The Section headings herein are for convenience only and shall not affect the construction hereof.

If the foregoing is in accordance with your understanding of our agreement, please sign and return to the Company and the Selling Shareholder a counterpart hereof, whereupon this instrument, along with all counterparts, will become a binding agreement among the Underwriters, the Company and the Selling Shareholder in accordance with its terms.


Very truly yours,

PROTHENA CORPORATION PLC

By		/s/ ▇▇▇▇ ▇. ▇▇▇▇▇▇
		Name: ▇▇▇▇ ▇. ▇▇▇▇▇▇

		Title: Chief Executive Officer

ELAN SCIENCE ONE LIMITED

By		/s/ ▇▇▇▇ ▇▇▇▇▇▇▇
		Name: ▇▇▇▇ ▇▇▇▇▇▇▇

		Title: Director

CONFIRMED AND ACCEPTED,

as of the date first above written:

For themselves and as Representatives of the other Underwriters named in Schedule A hereto.

▇▇▇▇▇▇▇ LYNCH, PIERCE, ▇▇▇▇▇▇ & ▇▇▇▇▇

INCORPORATED

CITIGROUP GLOBAL MARKETS INC.

By: ▇▇▇▇▇▇▇ LYNCH, PIERCE, ▇▇▇▇▇▇ & ▇▇▇▇▇

INCORPORATED


By		/s/ ▇▇▇▇ ▇▇▇▇▇
		Authorized Signatory


By: CITIGROUP GLOBAL MARKETS INC.

By		/s/ ▇▇▇▇▇▇▇ ▇. ▇▇▇▇▇
		Authorized Signatory

SCHEDULE A

The initial public offering price per share for the Securities shall be $26.00.

The purchase price per share for the Securities to be paid by the several Underwriters shall be $24.96, being an amount equal to the initial public offering price set forth above less $1.04 per share, subject to adjustment in accordance with Section 2(b) for dividends or distributions declared by the Company and payable on the Initial Securities but not payable on the Option Securities.


Name of Underwriter	Number of Initial Securities
▇▇▇▇▇▇▇ Lynch, Pierce, ▇▇▇▇▇▇ & ▇▇▇▇▇ Incorporated		1,383,589
Citigroup Global Markets Inc.		1,383,588

Total		2,767,177

Schedule A

SCHEDULE B


	Number of Initial Securities to be Sold		Maximum Number of Option Securities to be Sold
Elan Science One Limited		2,767,177		415,076

Total		2,767,177		415,076

Schedule B

SCHEDULE C-1

Pricing Terms

1. The Selling Shareholder is selling an aggregate of 2,767,177 Ordinary Shares.

2. The Selling Shareholder has granted an option to the Underwriters, severally and not jointly, to purchase up to an additional 415,076 Ordinary Shares.

3. The initial public offering price per share for the Securities shall be $26.00.

Schedule C-1

SCHEDULE C-2

Free Writing Prospectuses

None

Schedule C-2

SCHEDULE D

List of Persons and Entities Subject to Lock-up

▇▇▇▇▇ ▇. ▇▇▇▇▇▇

▇▇▇▇▇▇ ▇. ▇▇▇▇▇▇

▇▇▇▇ ▇. ▇▇▇▇▇

▇▇▇▇ ▇. ▇▇▇▇▇▇

▇▇▇▇▇▇▇ ▇. ▇▇▇▇▇▇▇

▇▇▇▇▇ ▇▇▇▇▇

▇▇▇▇▇▇▇▇▇▇▇ ▇. ▇▇▇▇▇▇

▇▇▇▇ ▇▇▇▇▇▇

▇▇▇▇▇▇ ▇▇▇▇▇▇

▇▇▇▇ ▇▇▇▇▇▇▇▇▇

Elan Science One Limited

Schedule D

PROTHENA CORPORATION PLC (an Irish public limited company) 2,767,177 Ordinary Shares UNDERWRITING AGREEMENT

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