Schedule 13G/A: William Scully Discloses Near-10% Stake in Prothena

Rhea-AI Filing Summary

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.

Positive

• Material stake disclosed: Aggregate beneficial ownership of 5,351,846 shares (~9.94%) is clearly reported.
• Clear breakdown of control: Filing specifies 768,000 shares with sole voting/dispositive power and 4,583,846 with shared power, improving transparency.

Negative

• None.

Insights

Financial Analyst

TL;DR: A near-10% stake is material; it signals a significant investor position without an asserted intent to change control.

The filing discloses an aggregate position of 5,351,846 shares (≈9.94%), split between sole and shared voting/dispositive powers. For investors, a holder approaching 10% can be important for shareholder dynamics, potential engagement, and voting outcomes. The certification that the position was not acquired to influence control implies passive or investment-oriented intent, but the size alone makes this an item of interest for governance and possible future disclosures.

Corporate Governance Expert

TL;DR: The combination of sole and shared control across trusts and funds creates governance complexity despite an asserted non-control intent.

The record shows 768,000 shares with sole power and 4,583,846 shares with shared power due to trusts, IRAs and managed accounts. Shared dispositive or voting power through trust features and substitution rights can complicate clear attribution of influence. Stake concentration near 10% warrants monitoring of any future amendments or coordinated actions that could change governance dynamics.

SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

SCHEDULE 13G

UNDER THE SECURITIES EXCHANGE ACT OF 1934

(Amendment No. 4)

PROTHENA CORP PUBLIC LTD CO

(Name of Issuer)

Ordinary Shares, $0.01 par value

(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

SCULLY WILLIAM P

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

FLORIDA

Number of Shares Beneficially Owned by Each Reporting Person With:

5	Sole Voting Power 768,000.00
6	Shared Voting Power 4,583,846.00
7	Sole Dispositive Power 768,000.00
8	Shared Dispositive Power 4,583,846.00

9

Aggregate Amount Beneficially Owned by Each Reporting Person

5,351,846.00

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)

9.9 %

12

Type of Reporting Person (See Instructions)

IN

Comment for Type of Reporting Person: See Item 4

SCHEDULE 13G

Item 1.
(a)	Name of issuer: PROTHENA CORP PUBLIC LTD CO
(b)	Address of issuer's principal executive offices: 77 SIR JOHN ROGERSON'S QUAY, BLOCK C, 77 SIR JOHN ROGERSON'S QUAY, BLOCK C, DUBLIN 2, IRELAND, D02 VK60.
Item 2.
(a)	Name of person filing: William P. Scully
(b)	Address or principal business office or, if none, residence: 771 Manatee Cove, Vero Beach, Florida 32963
(c)	Citizenship: Florida
(d)	Title of class of securities: Ordinary Shares, $0.01 par value
(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 Reporting Person may be deemed to be the beneficial owner of 5,351,846 Ordinary Shares. This amount consists of (i) 5,000 Ordinary Shares owned directly by the Reporting Person over which he has sole voting and dispositive power, (ii) 80,000 Ordinary Shares owned by Manatee Equity Fund LLC, of which the Reporting Person is the sole manager with sole voting and dispositive power, (iii) 683,000 Ordinary Shares owned by the Reporting Persons IRA, over which he has sole voting and dispositive power, (iv) 42,000 Ordinary Shares owned by the Reporting Persons spouses IRA, over which he may be deemed to have shared voting and dispositive power, (v) 10,000 Ordinary Shares owned by the Reporting Persons spouse, over which he may be deemed to have shared voting and dispositive power (vi) 23,000 Ordinary Shares owned by an IRA subject to an investment management agreement over which the Reporting Person may be deemed to have shared voting and dispositive power by reason of his right to terminate such agreement, (vii) 158,000 Ordinary Shares owned in the aggregate by various trusts, of which the Reporting Person may be deemed to have shared voting and dispositive power by virtue of being a co-trustee, (viii) 4,310,846 Ordinary Shares owned in the aggregate by various grantor retained annuity trusts, which have an independent trustee, but over which the Reporting Person may be deemed to have shared voting and dispositive power by reason of his retained right to substitute assets in such trusts, and (ix) 40,000 Ordinary Shares owned by another trust, which has an independent trustee, but over which the Reporting Person may be deemed to have shared voting and dispositive power by reason of his retained right to substitute assets in such trust.
(b)	Percent of class: According to the Issuers most recent Quarterly Report on Form 10-Q for the quarter ended June 30, 2025, the number of shares outstanding as of July 25, 2025 was 53,826,982. The Ordinary Shares which the Reporting Person may be deemed to beneficially own constitute approximately 9.94 percent of such total number of shares
(c)	Number of shares as to which the person has:
	(i) Sole power to vote or to direct the vote: 768,000
	(ii) Shared power to vote or to direct the vote: 4,583,846
	(iii) Sole power to dispose or to direct the disposition of: 768,000
	(iv) Shared power to dispose or to direct the disposition of: 4,583,846
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.
	Not Applicable
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 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.

SCULLY WILLIAM P

Signature:	/s/ Diana L. Hayes
Name/Title:	attorney-in-fact
Date:	08/13/2025

Comments accompanying signature: Pursuant to a limited power of attorney dated February 13, 2024, a copy of which is on file with the Commission

FAQ

How many Prothena (PRTA) shares does William P. Scully beneficially own?

The filing states Mr. Scully may be deemed the beneficial owner of 5,351,846 ordinary shares of Prothena.

What percentage of Prothena does Scully's stake represent?

The disclosed shares represent approximately 9.94% of the issuer's outstanding shares based on 53,826,982 shares outstanding.

How is Scully's voting and dispositive power divided?

He has sole voting/dispositive power over 768,000 shares and shared voting/dispositive power over 4,583,846 shares.

Through which vehicles are the shares held?

Holdings include direct ownership, Manatee Equity Fund LLC, multiple IRAs, various trusts, grantor retained annuity trusts, and another trust with substitution rights.

Does the filing state intent to influence control of Prothena?

The certifying statement declares the securities were not acquired and are not held for the purpose of changing or influencing control of the issuer.