[8-K] Prothena Corporation plc Reports Material Event

Rhea-AI Filing Summary

Davidson Kempner affiliates disclose a near-maximum 9.9% passive stake in Biora Therapeutics (BIOR). On 30 Jun 2025 the hedge-fund complex — M.H. Davidson & Co., Davidson Kempner Arbitrage, Equities & Relative Value LP, Davidson Kempner Capital Management LP and Managing Member Anthony A. Yoseloff — filed Amendment No. 1 to Schedule 13G.

• Total beneficial ownership: up to 906,227 common shares (including 851,177 issuable on note conversion), representing 9.90 % of BIOR’s 4,552,702 outstanding shares.
• Structure: All voting and dispositive power is shared; none of the entities have sole power.
• Convertible notes: 91 % of the reported position is in notes convertible into equity, but conversions are capped by a 9.90 % blocker, limiting immediate dilution.
• M.H. Davidson & Co. separately lists 25,624 shares (0.56 %) including 24,033 from notes.
• The group certifies the position is passive (Rule 13d-1(c)) and not intended to influence control.

The disclosure signals a sizable institutional bet on BIOR while highlighting potential dilution from convertible securities, though the blocker tempers near-term ownership expansion.

Positive

• Institutional validation: A well-known hedge fund complex committing up to 9.9 % of BIOR may boost market confidence and liquidity.

Negative

• Potential dilution: 851,177 shares are issuable from convertible notes, creating an overhang once the 9.9 % blocker constraint eases.

Insights

Equity Analyst

TL;DR – Hedge fund holds 9.9 % via notes, signalling confidence but creating convertible overhang.

Davidson Kempner’s 906 k-share exposure (almost entirely via convertibles) equals the legal ownership ceiling. For a micro-cap with <5 m shares outstanding, this stake is material, adding a sophisticated investor whose interests align with share appreciation. However, the heavy use of notes foreshadows dilution once the blocker lapses or if the base increases. Investors should track any future 13D moves that could indicate an activist tilt.

Corporate Governance Specialist

TL;DR – Passive filing limits immediate governance impact; monitor for 13D shift.

The Schedule 13G confirms Davidson Kempner is currently passive, mitigating control-change risk. Shared voting rights across entities concentrate influence in Yoseloff, but the 9.9 % cap prevents majority leverage. Should the fund re-file on Schedule 13D, governance dynamics could change rapidly, especially in light of convertible note triggers.

0001559053FALSE00015590532025-08-042025-08-04

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

WASHINGTON, D.C. 20549

_______________________________________________________

FORM 8-K 

_______________________________________________________

CURRENT REPORT

Pursuant to Section 13 or 15(d) of the

Securities Exchange Act of 1934

Date of Report (Date of earliest event reported): August 4, 2025

_______________________________________________________

PROTHENA CORPORATION PUBLIC LIMITED COMPANY

(Exact name of registrant as specified in its charter)

_______________________________________________________

Ireland

001-35676

98-1111119

(State or Other Jurisdiction of Incorporation)

(Commission File Number)

(IRS Employer Identification No.)

77 Sir John Rogerson's Quay, Block C

Grand Canal Docklands

Dublin 2,

D02 VK60,

Ireland

(Address of principal executive offices, including Zip Code)

Registrant’s telephone number, including area code: 011-353-1-236-2500

___________________________________________________

(Former Name or Former Address, if Changed Since Last Report.) 

___________________________________________________

Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions (see General Instruction A.2. below):

☐ Written communications pursuant to Rule 425 under the Securities Act (17 CFR 230.425)

☐ Soliciting material pursuant to Rule 14a-12 under the Exchange Act (17 CFR 240.14a-12)

☐ Pre-commencement communications pursuant to Rule 14d-2(b) under the Exchange Act (17 CFR 240.14d-2(b))

☐ Pre-commencement communications pursuant to Rule 13e-4(c) under the Exchange Act (17 CFR 240.13e-4(c))

Securities registered pursuant to Section 12(b) of the Act:

Title of Each Class			Trading Symbol			Name of Each Exchange on Which Registered
Ordinary Shares, par value $0.01 per share			PRTA			The Nasdaq Global Select Market

Indicate by check mark whether the registrant is an emerging growth company as defined in as defined in Rule 405 of the Securities Act of 1933 (§230.405 of this chapter) or Rule 12b-2 of the Securities Exchange Act of 1934 (§240.12b-2 of this chapter).

                                        Emerging growth company ☐

If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act. ☐

Item 2.02. Results of Operations and Financial Condition.

    The information in Item 2.02 of this Current Report on Form 8-K and Exhibit 99.1 attached hereto shall not be deemed “filed” for purposes of Section 18 of the Securities Exchange Act of 1934, as amended (the “Exchange Act”), or otherwise subject to the liabilities of that section. It may only be incorporated by reference in another filing under the Exchange Act or the Securities Act of 1933, as amended, if such subsequent filing specifically incorporate by reference the information furnished pursuant to Item 2.02 (including Exhibit 99.1) of this Current Report.

    On August 4, 2025, Prothena Corporation plc issued a press release announcing its financial results for the second quarter ended June 30, 2025. A copy of that press release is furnished as Exhibit 99.1 to this Current Report on Form 8-K and is incorporated herein by reference.

Item 9.01. Financial Statements and Exhibits

(d) Exhibits.

Exhibit No.						Description
99.1						Press Release dated August 4, 2025
104						Cover Page Interactive Data File (embedded within the Inline XBRL document)

SIGNATURES

    Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized.

Date:

August 4, 2025

PROTHENA CORPORATION PLC

By:

/s/ Tran B. Nguyen

Name:

Tran B. Nguyen

Title:

Chief Financial Officer and Chief Strategy Officer

FAQ

How much of Biora Therapeutics (BIOR) does Davidson Kempner own?

The group reports beneficial ownership of up to 906,227 shares, or 9.90 % of outstanding common stock.

What is the composition of the reported BIOR stake?

Approximately 91 % of the position comes from notes convertible into common shares; the remainder is currently outstanding stock.

Does the filing indicate activist intent toward BIOR?

No. The Schedule 13G filing and certification state the securities are held for passive investment purposes.

What is the 9.90 % blocker mentioned in the filing?

The notes prohibit conversion that would push the group’s ownership above 9.90 %, limiting immediate voting power and dilution.

Could the convertible notes dilute existing BIOR shareholders?

Yes. If and when the blocker is lifted or the share count rises, 851,177 additional shares could enter the market.