Power of Attorney for William P. Scully

This filing is an exhibit (Exhibit 24) detailing a Power of Attorney granted by William P. Scully to Reid E. Buchanan, Diana L. Hayes, and Todd W. Fennell. The attorneys-in-fact are authorized to act on behalf of Mr. Scully in all matters related to his filings with the U.S. Securities and Exchange Commission (SEC). This includes preparing and executing necessary forms such as Forms 3, 4, and 5, as well as Schedules 13D and 13G, using the SEC's EDGAR system. They are also empowered to manage Mr. Scully's EDGAR account, obtain information about his transactions in Prothena Corp Public Ltd Co securities from third parties, and generally perform all actions necessary for compliance with Section 13 and 16 of the Securities Exchange Act of 1934 and Rule 144 of the Securities Act of 1933. The Power of Attorney explicitly states that it authorizes action at the discretion of the attorneys-in-fact and does not relieve Mr. Scully of his ultimate responsibility for compliance. The document is dated September 4, 2025, and revokes all previous powers of attorney related to this subject matter.