Company: PRTA
Filing Date: 2025-03-28
Form Type: DEFA14A
Source: 0001140361-25-011006
Chunk: 0

Company: PROTHENA CORP PUBLIC LTD CO
Filing Date: 2025-03-28
Form: DEFA14A
Chunk 0
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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

| Filed by the Registrant | ☒ |     | Filed by a Party other than the Registrant | ☐ |

Check the appropriate box:

| ☐ | Preliminary Proxy Statement |

| ☐ | Confidential, for Use of the Commission Only (as permitted by Rule 14a-6(e)(2)) |

| ☐ | Definitive Proxy Statement |

| ☒ | Definitive Additional Materials |

| ☐ | Soliciting Material Pursuant to § 240.14a-12 |

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):

| ☒ | No fee required.                                                                                    |
| ☐ | Fee paid previously with preliminary materials.                                                     |
| ☐ | Fee computed on table in exhibit required by Item 25(b) per Exchange Act Rules 14a-6(i)(1) and 0-11 |