Company: PRTA
Filing Date: 2025-03-28
Form Type: DEF 14A
Source: 0001559053-25-000017
Chunk: 11

Company: PROTHENA CORP PUBLIC LTD CO
Filing Date: 2025-03-28
Form: DEF 14A
Chunk 11
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 in next year's proxy materials, your proposal must comply with the requirements of Rule 14a-8 of the Exchange Act and other SEC rules and be submitted in writing no later than November 28, 2025, to our Company Secretary at Prothena Corporation plc, 77 Sir John Rogerson’s Quay, Block C, Grand Canal Docklands, Dublin 2, D02 VK60, Ireland; provided that if the date of next year's annual general meeting of shareholders is greater than 30 days from May 13, 2026, the deadline is a reasonable time before we begin to print and send our proxy materials for next year’s annual general meeting.

For a shareholder to make any formal nomination of a director candidate for election to the Board at the 2026 annual general meeting of shareholders, the shareholder must provide notice to the Company not earlier than October 29, 2025, and not later than December 28, 2025, and must otherwise comply with the requirements set forth in our Constitution. You are advised to review our Constitution, which contains additional requirements about advance notice of director nominations. For more information, see below under the heading Corporate Governance and Board Matters - Board Committees - Nominating and Corporate Governance Committee.

In addition to satisfying the requirements regarding director nominations in our Constitution, to comply with the universal proxy rules, shareholders who intend to solicit proxies in support of director

| 2025 PROXY STATEMENT |     | 5 |

TABLE OF CONTENTS

| THE PROXY PROCESS AND SHAREHOLDER VOTING                     |
| QUESTIONS AND ANSWERS ABOUT THESE PROXY MATERIALS AND VOTING |

nominees other than the Company’s nominees must provide notice that sets forth the information required

by Rule 14a-19 under the Exchange Act no later than March 14, 2026.

| 14. |     | What is the quorum requirement? |

A quorum of shareholders is necessary to hold a valid meeting. A quorum will be present if the holders of not less than one-half of the ordinary shares issued and outstanding and entitled to vote are present in person or represented by proxy at the Annual Meeting. On the Record Date, there were 53,826,982 ordinary shares issued and outstanding and entitled to vote. Accordingly, 26,913,491 ordinary shares must be represented in person or by proxy at the Annual Meeting to have a quorum.

Your shares will be counted towards the quorum if you submit a valid proxy vote or