PROTHENA CORP PUBLIC LTD CO

DEF 14A 1 ny20053507x2_def14a.htm DEF 14A

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

SCHEDULE 14A

Proxy Statement Pursuant to Section 14(a) of the

Securities Exchange Act of 1934

Check the appropriate box:

PROTHENA CORPORATION PUBLIC LIMITED COMPANY

(Name of registrant as specified in its charter)

(Name of Person(s) Filing Proxy Statement, if other than the Registrant)

Payment of Filing Fee (Check all boxes that apply):

October 7, 2025

Dear Shareholder:

You are cordially invited to attend the Extraordinary General Meeting of Shareholders (the “EGM”) of Prothena Corporation plc (the “Company”) to be held on Wednesday, November 19, 2025, at 4:00 p.m. local time, at the offices of A&L Goodbody LLP, 25 North Wall Quay, Dublin 1, D01 H104, Ireland.

Details of the business to be presented at the EGM may be found in the Notice of Extraordinary General Meeting of Shareholders and the Proxy Statement accompanying this letter. At the EGM, we are asking shareholders to approve a reduction of our Company capital to facilitate the creation of distributable reserves. The reduction of capital will give our Board of Directors greater flexibility with respect to its ability to make future distributions to shareholders, including by way of a potential share redemption program as referenced in our press release dated August 4, 2025.

We hope that you will participate in the meeting by voting through acceptable means as described in this Proxy Statement as promptly as possible. Your vote is important – so please exercise your right.

Sincerely,

This Proxy Statement and the enclosed proxy card are being made available to shareholders on or about October 7, 2025.

PROTHENA CORPORATION PLC

Registered in Ireland - No. 518146

77 Sir John Rogerson’s Quay, Block C, Grand Canal

Docklands, Dublin 2, D02 VK60, Ireland

NOTICE OF EXTRAORDINARY GENERAL MEETING OF SHAREHOLDERS TO BE HELD ON NOVEMBER 19, 2025

To the Shareholders of Prothena Corporation plc:

NOTICE IS HEREBY GIVEN that an Extraordinary General Meeting of Shareholders (the “EGM”) of Prothena Corporation plc, an Irish public limited company (the “Company”), will be held on Wednesday, November 19, 2025, at 4:00 p.m. local time, at the offices of the Company’s legal counsel, A&L Goodbody LLP, 25 North Wall Quay, Dublin 1, D01 H104, Ireland, for the following purposes:

The text of Proposal No.1 is set out in the Proxy Statement accompanying this Notice. Pursuant to our Constitution and Irish law, Proposal No. 1 is being proposes as a special resolution requiring the approval of at least 75% of the votes cast at the EGM.

Only shareholders who owned our ordinary shares at the close of business on September 24, 2025, may vote at the EGM. Each shareholder of record will be entitled to one vote per ordinary share on each matter submitted to a vote of the shareholders, as long as those shares are represented at the EGM, either in person or by proxy. Shareholders who are entitled to attend and vote at the EGM are entitled to appoint a proxy or proxies to attend and vote on their behalf at the EGM; such proxy is not required to be a shareholder of the Company.

Our Board of Directors unanimously recommends that you vote FOR the approval of the reduction of the Company’s capital to facilitate the creation of distributable reserves, as described in Proposal No. 1.

For the EGM, we have elected to use the internet as the primary means of providing our proxy materials to shareholders. Consequently, some shareholders may not receive paper copies of our proxy materials. We intend to send shareholders a Notice of Internet Availability of Proxy Materials with instructions for accessing the proxy materials and for voting via the internet. The Notice of Internet Availability of Proxy Materials will also provide the date, time, and location of the EGM; the matters to be acted upon at the meeting and the Board of Directors’ recommendation with regard to each matter; a toll-free number, an e-mail address, and a website where shareholders can request a paper or e-mail copy of our Proxy Statement and form of proxy card; information on how to access their proxy card; and information on how to attend the meeting and vote in person.

You are cordially invited to attend the EGM, but whether or not you expect to attend in person, you are urged to complete, sign, and date your proxy card and return it by mail or follow the alternative voting procedures described in the Notice of Internet Availability of Proxy Materials or the proxy card.

By Order of the Board of Directors