[SCHEDULE 13G] Prothena Corporation plc SEC Filing

Rhea-AI Filing Summary

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.

Positive

• Material stake disclosed: Reports beneficial ownership of 3,375,009 shares (6.3%), which is a significant, reportable position.
• Transparency among affiliates: Filing details allocation between ADAR1 Partners, LP (2,892,995 shares) and Spearhead Insurance Solutions IDF, LLC (482,014 shares) and includes a Joint Filing Agreement.
• Clear classification: Filed on Schedule 13G with a certification stating holdings are in the ordinary course of business and not intended to influence control.

Negative

• None.

Insights

Financial Analyst

TL;DR: ADAR1 group disclosed a passive 6.3% stake (3.375M shares) in PRTA, filed on Schedule 13G, indicating non-control intent.

The filing reports a combined beneficial ownership of 3,375,009 ordinary shares, representing 6.3% of Prothena's 53,826,982 shares outstanding. The cover page allocation shows 2,892,995 shares held by ADAR1 Partners, LP and 482,014 shares held by Spearhead Insurance Solutions IDF, LLC. ADAR1 Capital Management, LLC states shared voting and dispositive power; the Schedule 13G classification and the certification language indicate the position is held in the ordinary course of business and not for control. For investors, this disclosure provides clarity on a meaningful passive holder but contains no operational or financial projections.

Corporate Governance Expert

TL;DR: This is a standard Schedule 13G passive ownership disclosure showing shared control among affiliated entities and an individual.

The document identifies three reporting persons: ADAR1 Capital Management, LLC (investment adviser), ADAR1 Capital Management GP, LLC (general partner), and Daniel Schneeberger (manager/individual). The filing attributes shared voting and dispositive power over the reported shares to the adviser and related entities. The Schedule 13G classification and the signed certification assert the holdings were not acquired to influence control. The exhibit list includes a Joint Filing Agreement, consistent with coordinated reporting among affiliates.

SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

SCHEDULE 13G

UNDER THE SECURITIES EXCHANGE ACT OF 1934

Prothena Corporation Public Limited Company

(Name of Issuer)

Ordinary Shares, par value $0.01 per share

(Title of Class of Securities)

G72800108

(CUSIP Number)

06/30/2025

(Date of Event Which Requires Filing of this Statement)

Check the appropriate box to designate the rule pursuant to which this Schedule is filed:

Rule 13d-1(b)

Rule 13d-1(c)

Rule 13d-1(d)

SCHEDULE 13G

CUSIP No. G72800108

1

Names of Reporting Persons

ADAR1 Capital Management, LLC

2

Check the appropriate box if a member of a Group (see instructions)

(a)
(b)

3

Sec Use Only

4

Citizenship or Place of Organization

TEXAS

Number of Shares Beneficially Owned by Each Reporting Person With:

5	Sole Voting Power 0.00
6	Shared Voting Power 3,375,009.00
7	Sole Dispositive Power 0.00
8	Shared Dispositive Power 3,375,009.00

9

Aggregate Amount Beneficially Owned by Each Reporting Person

3,375,009.00

10

Check box if the aggregate amount in row (9) excludes certain shares (See Instructions)

11

Percent of class represented by amount in row (9)

6.3 %

12

Type of Reporting Person (See Instructions)

IA, OO

Comment for Type of Reporting Person: Includes (i) 2,892,995 ordinary shares, par value $0.01 per share ("Ordinary Shares") held by ADAR1 Partners, LP and (ii) 482,014 ordinary shares held by Spearhead Insurance Solutions IDF, LLC as of June 30, 2025. As the investment manager of ADAR1 Partners, LP and as the sub-advisor of Spearhead Insurance Solutions IDF, LLC, ADAR1 Capital Management, LLC may be deemed to indirectly beneficially own securities held by ADAR1 Partners, LP and Spearhead Insurance Solutions IDF, LLC. Based on 53,826,982 ordinary shares of Prothena Corporation Public Limited Company (the "Issuer") outstanding as of June 30, 2025 reported in the Issuer's 10-Q, filed with the SEC on August 4, 2025.

SCHEDULE 13G

CUSIP No. G72800108

1

Names of Reporting Persons

ADAR1 Capital Management GP, LLC

2

Check the appropriate box if a member of a Group (see instructions)

(a)
(b)

3

Sec Use Only

4

Citizenship or Place of Organization

TEXAS

Number of Shares Beneficially Owned by Each Reporting Person With:

5	Sole Voting Power 0.00
6	Shared Voting Power 2,892,995.00
7	Sole Dispositive Power 0.00
8	Shared Dispositive Power 2,892,995.00

9

Aggregate Amount Beneficially Owned by Each Reporting Person

2,892,995.00

10

Check box if the aggregate amount in row (9) excludes certain shares (See Instructions)

11

Percent of class represented by amount in row (9)

5.4 %

12

Type of Reporting Person (See Instructions)

OO

Comment for Type of Reporting Person: Includes 2,892,995 ordinary shares, $0.01 per share ("Ordinary Shares") held by ADAR1 Partners, LP as of June 30, 2025. As the general partner of ADAR1 Partners, LP, ADAR1 Capital Management GP, LLC may be deemed to indirectly beneficially own securities held by ADAR1 Partners, LP. Based on 53,826,982 ordinary shares of Prothena Corporation Public Limited Company (the "Issuer") outstanding as of June 30, 2025 reported in the Issuer's 10-Q, filed with the SEC on August 4, 2025.

SCHEDULE 13G

CUSIP No. G72800108

1

Names of Reporting Persons

Daniel Schneeberger

2

Check the appropriate box if a member of a Group (see instructions)

(a)
(b)

3

Sec Use Only

4

Citizenship or Place of Organization

SWITZERLAND

Number of Shares Beneficially Owned by Each Reporting Person With:

5	Sole Voting Power 0.00
6	Shared Voting Power 2,892,995.00
7	Sole Dispositive Power 0.00
8	Shared Dispositive Power 2,892,995.00

9

Aggregate Amount Beneficially Owned by Each Reporting Person

2,892,995.00

10

Check box if the aggregate amount in row (9) excludes certain shares (See Instructions)

11

Percent of class represented by amount in row (9)

5.4 %

12

Type of Reporting Person (See Instructions)

HC, IN

Comment for Type of Reporting Person: Includes (i) 2,892,995 ordinary shares, par value $0.01 per share ("Ordinary Shares") held by ADAR1 Partners, LP and (ii) 482,014 ordinary shares held by Spearhead Insurance Solutions IDF, LLC as of June 30, 2025. As the manager of ADAR1 Capital Management, LLC and ADAR1 Capital Management GP, LLC, Mr. Schneeberger may be deemed to indirectly beneficially own securities held by ADAR1 Partners, LP and Spearhead Insurance Solutions IDF, LLC. Based on 53,826,982 ordinary shares of Prothena Corporation Public Limited Company (the "Issuer") outstanding as of June 30, 2025 reported in the Issuer's 10-Q, filed with the SEC on August 4, 2025.

SCHEDULE 13G

Item 1.
(a)	Name of issuer: Prothena Corporation Public Limited Company
(b)	Address of issuer's principal executive offices: 77 Sir John Rogerson's Quay, Block C Grand Canal Docklands Dublin 2, L2, D02 VK60
Item 2.
(a)	Name of person filing: This Schedule is being filed on behalf of each of the following persons (each, a "Reporting Person" and collectively, the "Reporting Persons"): (i) ADAR1 Capital Management, LLC ("ADAR1 Capital Management"); (ii) ADAR1 Capital Management GP, LLC ("ADAR1 General Partner"); and (iii) Daniel Schneeberger ("Mr. Schneeberger").
(b)	Address or principal business office or, if none, residence: The address of the principal business office of each of the Reporting Persons is 3503 Wild Cherry Drive, Building 9, Austin, Texas 78738.
(c)	Citizenship: (i) ADAR1 Capital Management is a Texas limited liability company; (ii) ADAR1 General Partner is a Texas limited liability company; and (iii) Mr. Schneeberger is a citizen of Switzerland.
(d)	Title of class of securities: Ordinary Shares, par value $0.01 per share
(e)	CUSIP No.: G72800108
Item 3.	If this statement is filed pursuant to §§ 240.13d-1(b) or 240.13d-2(b) or (c), check whether the person filing is a:
(a)	Broker or dealer registered under section 15 of the Act (15 U.S.C. 78o);
(b)	Bank as defined in section 3(a)(6) of the Act (15 U.S.C. 78c);
(c)	Insurance company as defined in section 3(a)(19) of the Act (15 U.S.C. 78c);
(d)	Investment company registered under section 8 of the Investment Company Act of 1940 (15 U.S.C. 80a-8);
(e)	An investment adviser in accordance with § 240.13d-1(b)(1)(ii)(E);
(f)	An employee benefit plan or endowment fund in accordance with § 240.13d-1(b)(1)(ii)(F);
(g)	A parent holding company or control person in accordance with § 240.13d-1(b)(1)(ii)(G);
(h)	A savings associations as defined in Section 3(b) of the Federal Deposit Insurance Act (12 U.S.C. 1813);
(i)	A church plan that is excluded from the definition of an investment company under section 3(c)(14) of the Investment Company Act of 1940 (15 U.S.C. 80a-3);
(j)	A non-U.S. institution in accordance with § 240.13d-1(b)(1)(ii)(J). If filing as a non-U.S. institution in accordance with § 240.13d-1(b)(1)(ii)(J), please specify the type of institution:
(k)	Group, in accordance with Rule 240.13d-1(b)(1)(ii)(K).
Item 4.	Ownership
(a)	Amount beneficially owned: The information contained on the cover pages of this Schedule 13G is incorporated herein by reference.
(b)	Percent of class: The information contained on the cover pages of this Schedule 13G is incorporated herein by reference.
(c)	Number of shares as to which the person has:
	(i) Sole power to vote or to direct the vote: The information contained on the cover pages of this Schedule 13G is incorporated herein by reference.
	(ii) Shared power to vote or to direct the vote: The information contained on the cover pages of this Schedule 13G is incorporated herein by reference.
	(iii) Sole power to dispose or to direct the disposition of: The information contained on the cover pages of this Schedule 13G is incorporated herein by reference.
	(iv) Shared power to dispose or to direct the disposition of: The information contained on the cover pages of this Schedule 13G is incorporated herein by reference.
Item 5.	Ownership of 5 Percent or Less of a Class.
Item 6.	Ownership of more than 5 Percent on Behalf of Another Person.
	Not Applicable
Item 7.	Identification and Classification of the Subsidiary Which Acquired the Security Being Reported on by the Parent Holding Company or Control Person.
	If a parent holding company has filed this schedule, pursuant to Rule 13d-1(b)(ii)(G), so indicate under Item 3(g) and attach an exhibit stating the identity and the Item 3 classification of the relevant subsidiary. If a parent holding company has filed this schedule pursuant to Rule 13d-1(c) or Rule 13d-1(d), attach an exhibit stating the identification of the relevant subsidiary. Mr. Schneeberger is filing this Schedule 13G as a control person in respect of shares beneficially owned by ADAR1 Capital Management, an investment adviser as described in SS 240.13d-1(b)(1)(ii)(E).
Item 8.	Identification and Classification of Members of the Group.
	Not Applicable
Item 9.	Notice of Dissolution of Group.
	Not Applicable

Item 10.

Certifications:

By signing below I certify that, to the best of my knowledge and belief, the securities referred to above were acquired and are held in the ordinary course of business and were not acquired and are not held for the purpose of or with the effect of changing or influencing the control of the issuer of the securities and were not acquired and are not held in connection with or as a participant in any transaction having that purpose or effect, other than activities solely in connection with a nomination under ?? 240.14a-11.

SIGNATURE

After reasonable inquiry and to the best of my knowledge and belief, I certify that the information set forth in this statement is true, complete and correct.

ADAR1 Capital Management, LLC

Signature:	/s/ Daniel Schneeberger
Name/Title:	Daniel Schneeberger, Manager
Date:	08/14/2025

ADAR1 Capital Management GP, LLC

Signature:	/s/ Daniel Schneeberger
Name/Title:	Daniel Schneeberger, Manager
Date:	08/14/2025

Daniel Schneeberger

Signature:	/s/ Daniel Schneeberger
Name/Title:	Daniel Schneeberger, in his individual capacity
Date:	08/14/2025

Exhibit Information

Exhibit A: Joint Filing Agreement

FAQ

What stake in Prothena (PRTA) does ADAR1 report?

The reporting persons disclose beneficial ownership of 3,375,009 ordinary shares, equal to 6.3% of outstanding shares as of June 30, 2025.

How are the 3,375,009 shares allocated among ADAR1-related entities?

2,892,995 shares are held by ADAR1 Partners, LP and 482,014 shares are held by Spearhead Insurance Solutions IDF, LLC.

Does the filing indicate ADAR1 seeks control of Prothena?

No. The Schedule 13G certification states the securities were acquired and are held in the ordinary course of business and were not acquired to change or influence control.

What voting and dispositive power is reported?

ADAR1 Capital Management, LLC reports 0 sole voting/dispositive power and 3,375,009 shared voting and shared dispositive power over the shares.

What outstanding share count is the percent ownership based on?

The percent is calculated using 53,826,982 ordinary shares outstanding as reported in the Issuer's 10-Q filed August 4, 2025.