Prothena (PRTA) Proxy Filing summary

Executive summary

• An Extraordinary General Meeting (EGM) is scheduled for November 19, 2025, in Dublin, Ireland, to consider a special resolution regarding the reduction of company capital to create distributable reserves.

• The reduction aims to provide the Board with flexibility for future distributions, including potential share redemptions or dividends, subject to Irish High Court approval.

• Shareholders of record as of September 24, 2025, are eligible to vote, with one vote per ordinary share.

• Proxy materials are primarily distributed via the internet, with options for mail or electronic delivery upon request.

Voting matters and shareholder proposals

• The main proposal is to approve a reduction of the share premium account to facilitate the creation of distributable reserves.

• Approval requires a special resolution with at least 75% of votes cast in favor at the EGM.

• Shareholders may also vote on any other business properly brought before the EGM.

• Shareholder proposals for the 2026 annual meeting must be submitted by November 28, 2025, and director nominations between October 29 and December 28, 2025.

Board of directors and corporate governance

• The Board unanimously recommends voting in favor of the capital reduction proposal.

• Shareholders may appoint proxies to vote on their behalf; proxies need not be shareholders themselves.