Company: PRTA
Filing Date: 2025-10-07
Form Type: DEF 14A
Source: 0001140361-25-037500
Chunk: 5

Company: PROTHENA CORP PUBLIC LTD CO
Filing Date: 2025-10-07
Form: DEF 14A
Chunk 5
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 accompanying form of proxy card will vote on such matter in accordance with his or her discretion.

| 3. |     | How do I vote? |

You may vote by mail or follow any alternative voting procedure described on the proxy card or the Notice of Internet Availability of Proxy Materials. To use an alternative voting procedure, follow the instructions on each proxy card that you receive or on the Notice of Internet Availability of Proxy Materials. For Proposal No. 1, you may vote “FOR” or “AGAINST” or abstain from voting. The procedures for voting are as follows: Shareholder of Record: Shares Registered in Your Name If you are a shareholder of record, you may vote in person at the EGM. Alternatively, you may vote by proxy by mail, over the internet, or by telephone. Whether or not you plan to attend the EGM, we urge you to vote by proxy to

ensure your vote is counted. Even if you have submitted a proxy before the EGM, you may still attend the EGM and vote in person. In such case, your previously submitted proxy will be disregarded.

| • | To vote in person, come to the EGM and we will give you a ballot when you arrive. |

| • | To vote using the proxy card, simply complete, sign, and date the proxy card and return it promptly in the envelope provided. If you return your signed proxy card to us before the EGM, we will vote your shares as you direct. |

| • | To vote by proxy over the internet, follow the instructions provided on the proxy card or in the Notice of Internet Availability of Proxy Materials. |

| 2 |     | 2025 PROXY STATEMENT FOR EXTRAORDINARY GENERAL MEETING |

TABLE OF CONTENTS

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

| • | To vote by telephone if you request printed copies of the proxy materials by mail, you may vote by proxy by calling the toll-free number found on the proxy card. |

Beneficial Owner: Shares Registered in the Name of Broker, Bank, or Other Agent If you are a beneficial owner of shares registered in the name of your broker, bank, or other agent, who in turn hold through DTC, you should have received a voting instruction card and voting instructions with these proxy

materials from that organization rather than from us. Simply complete and mail the voting instruction card to ensure that your vote is counted