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Rubric Capital Management LP and David Rosen disclosed beneficial ownership of Prothena Corporation plc’s ordinary shares. They report holding 3,677,331 ordinary shares, representing 6.83% of the outstanding class.
The percentage is calculated based on 53,829,982 ordinary shares outstanding as of October 31, 2025, as reported by Prothena. Rubric Capital Master Fund LP has the right to receive dividends or sale proceeds on more than 5% of the shares. The investors state that the shares are held in the ordinary course of business and not for the purpose of changing or influencing control of Prothena.
Prothena Corporation plc disclosed that director Paula Cobb has decided to resign from its Board of Directors, effective December 31, 2025. Until that date, she will continue serving on the Board as well as on the Compensation Committee and the Audit Committee.
The company stated that Ms. Cobb’s decision to step down was not because of any disagreement with Prothena on matters related to its operations, policies, or practices, suggesting this is a routine governance change rather than a dispute-driven departure.
Prothena Corporation plc reported the results of an extraordinary general meeting of shareholders held on November 19, 2025. Shareholders considered a single proposal to approve a reduction of the Company’s capital to create distributable reserves.
The proposal was approved with 37,779,052 votes in favor, 46,738 against, and 45,906 abstentions. Creating distributable reserves is an Irish corporate law mechanism that can give a company more flexibility to make future distributions, such as dividends or other returns of value, if its board later chooses to do so and other legal requirements are met. This update reflects a change in Prothena’s capital structure authorization rather than an immediate financial transaction.
Prothena (PRTA) reported Q3 2025 results showing modest collaboration revenue and lower operating spend amid an ongoing restructuring. Total revenue was $2.4 million for the quarter and $9.7 million year-to-date. Research and development expense declined to $28.9 million in Q3, with program spend led by PRX012 ($14.7 million), followed by birtamimab ($7.1 million) and PRX019 ($2.2 million). General and administrative expense was $13.2 million in Q3; restructuring costs totaled $33.1 million year-to-date.
The company recorded a Q3 net loss of $36.5 million and a year-to-date net loss of $222.5 million. Cash and cash equivalents were $330.8 million as of September 30, 2025, compared with $471.4 million at year-end 2024, reflecting $140.3 million used in operating activities year-to-date. Shareholders’ equity was $295.0 million, with total assets of $352.6 million.
Prothena’s collaboration with BMS continues to contribute deferred revenue tied to the PRX019 Phase 1 clinical trial obligation, with $2.4 million recognized in Q3 and $2.7 million remaining as of quarter end. Ordinary shares outstanding were 53,829,982 as of October 31, 2025.
Prothena Corporation plc furnished a press release announcing its financial results for the third quarter ended September 30, 2025. The press release is attached as Exhibit 99.1 to a current report on Form 8-K dated November 6, 2025. The company states that the information provided under Item 2.02 and Exhibit 99.1 is furnished and not deemed “filed” under Section 18 of the Exchange Act.
Prothena Corporation plc is asking shareholders to approve a reduction of capital to create distributable reserves at an Extraordinary General Meeting to be held on November 19, 2025 at 4:00 p.m. local time in Dublin. The Board unanimously recommends a FOR vote on Proposal No. 1, which would permit the company to convert a portion of its capital into distributable reserves that can be used for dividends, share repurchases or other corporate purposes consistent with Irish law.
The Proxy Statement will be made available primarily via the internet on or about October 7, 2025 to shareholders of record as of the September 24, 2025 Record Date. There were 53,829,928 ordinary shares outstanding as of the Record Date. Voting may be done in person, by signed proxy card, by internet, or by telephone (if printed materials are requested). Advance director nomination windows are set for October 29, 2025 through December 28, 2025, and universal proxy notices must comply by March 14, 2026. Voting results will be filed within four business days after the meeting.
Prothena Corporation plc is soliciting proxies for an Extraordinary General Meeting on November 19, 2025 in Dublin to approve a proposed reduction of capital to create distributable reserves. The Board unanimously recommends a FOR vote on Proposal No. 1. Shareholders of record as of September 24, 2025 may vote; there were 53,829,928 ordinary shares outstanding on the Record Date. The company is primarily delivering proxy materials via the internet and will mail a Notice of Internet Availability; paper copies can be requested. Voting options include in-person, mail, internet, and telephone with revocation permitted until 11:59 p.m. ET on November 18, 2025. Procedures for director nominations for 2026 are specified with notice windows and universal proxy compliance dates.
Prothena Corporation plc filed a report stating that it issued a press release on August 27, 2025. The release provides an update on its PRX012 investigational drug and shares results from the Phase 1 ASCENT clinical program. The press release is included as Exhibit 99.1 and is incorporated by reference, meaning the detailed clinical information is contained in that exhibit rather than in this summary document.
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.