Prothena SEC Filings

ADAR1 Capital Management and related parties reported beneficial ownership of 3,375,009 ordinary shares of Prothena Corporation plc, representing 6.3% of the outstanding common stock as of June 30, 2025. The filing breaks the position into 2,892,995 shares held by ADAR1 Partners, LP and 482,014 shares held by Spearhead Insurance Solutions IDF, LLC. ADAR1 Capital Management, LLC reports shared voting and dispositive power over the full 3,375,009-share position. The filing cites 53,826,982 ordinary shares outstanding based on the Issuer's 10-Q filed August 4, 2025. The Schedule 13G is signed by Daniel Schneeberger on behalf of the reporting entities on August 14, 2025.

Prothena Corporation plc: Multiple related entities led by Logos Global and Dr. William Arsani jointly filed a Schedule 13G/A reporting zero beneficial ownership of the issuer's Ordinary Shares, representing 0% of the class. The filing states Logos Global acts as an investment adviser to funds (including a master fund) and identifies the general partner relationships among the reporting entities. The filers say they submitted the statement jointly but expressly disclaim membership in a group and disclaim beneficial ownership except to the extent of any pecuniary interest.

T. Rowe Price Associates, Inc. reports beneficial ownership of 71,047 shares of Prothena Corporation plc common stock, equal to about 0.1% of the outstanding class. The Schedule 13G filing shows T. Rowe Price has sole voting power and sole dispositive power over the shares and identifies the filer as an investment adviser. The filing states the position is held in the ordinary course of business and not for the purpose of changing or influencing control. Items addressing group membership, ownership on behalf of others, and related classifications are marked Not Applicable.

William P. Scully reports beneficial ownership of 5,351,846 ordinary shares of Prothena Corporation plc, representing approximately 9.94% of the issuer's outstanding shares based on the issuer's reported figure of 53,826,982 shares. The holdings combine direct ownership and interests across investment vehicles, including a direct stake, an LLC, multiple IRAs, trusts and grantor retained annuity trusts.

The filing breaks ownership into 768,000 shares over which Mr. Scully has sole voting and dispositive power and 4,583,846 shares over which he has shared voting and dispositive power, reflecting a mix of individually held shares and positions held through managed or trust arrangements.

Todd W. Fennell filed an amendment to a Schedule 13G disclosing beneficial ownership of 4,350,846 ordinary shares of Prothena Corporation plc, representing approximately 8.08% of the 53,826,982 shares outstanding. The reported holdings consist of 40,000 shares held by an irrevocable gift trust and 4,310,846 shares held by multiple grantor retained annuity trusts, for which Mr. Fennell serves as independent trustee.

The filing shows shared voting and shared dispositive power over all reported shares and includes a certification that the securities are not held to change or influence control of the issuer. This disclosure provides investors a clear view of a materially significant, statedly passive stake in PRTA and identifies the legal vehicles through which the interest is held.

Prothena Corporation plc has filed a registration statement to register ordinary shares issuable under its Prothena Corporation plc 2018 Long Term Incentive Plan, as amended. The filing incorporates by reference the companys existing public reports, including the Annual Report for the year ended December 31, 2024 and recent quarterly reports, to supply the required disclosure. The companys Constitution, as publicly filed, provides for indemnification of directors and certain executives to the extent permitted by Irish law, and the company maintains insurance and indemnification agreements for officers and directors. The exhibit list documents the Plan and multiple amendments (First through Sixth) and includes legal and auditor consents.