Prothena owner William P. Scully buys 100,000 shares

The reported prices are weighted averages across multiple purchases, with each transaction's stated per-share range.

Rhea-AI Filing Summary

Prothena Corp Public Ltd Co (PRTA) ten-percent owner William P. Scully directly purchased 100,000 ordinary shares on October 13, 2026, at a weighted average of $8.3548 per share, across prices from $8.2547 to $8.4616. He directly purchased 10,000 shares on October 14, 2026, at a weighted average of $8.4569 per share, across prices from $8.4000 to $8.5600. No Rule 10b5-1 plan is reported. As of October 13, 2026, indirect holdings included 529,000 shares held by his spouse and 187,000 shares held by Manatee Equity Fund LLC; Scully disclaimed beneficial ownership of the LLC shares except to the extent of his pecuniary interest.

Insider Trade Summary

Net Buyer: 110,000 shares

Net Buy 4 txns

Insider SCULLY WILLIAM P

Role 10% Owner

Bought 110,000 shs ($920K)

Type	Security	Shares	Price	Value
Purchase	Ordinary Shares, par value $0.01 per share F2	10,000	$8.4569	$85K
Purchase	Ordinary Shares, par value $0.01 per share F1	100,000	$8.3548	$835K
holding	Ordinary Shares, par value $0.01 per share	--	--	--
holding	Ordinary Shares, par value $0.01 per share F3	--	--	--

Holdings After Transaction: Ordinary Shares, par value $0.01 per share — 1,037,000 shares (Direct); Ordinary Shares, par value $0.01 per share — 529,000 shares (Indirect, By Spouse); Ordinary Shares, par value $0.01 per share — 187,000 shares (Indirect, By Manatee Equity Fund LLC)

Footnotes (3)

1. F1. The price reported in Column 4 is a weighted average price. These shares were purchased in multiple transactions at prices ranging from $8.2547 to $8.4616, inclusive. The reporting person undertakes to provide to Prothena Corp Public Ltd Co, any security holder of Prothena Corp Public Ltd Co, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the ranges set forth in footnotes (1) and (2) to this Form 4.
2. F2. The price reported in Column 4 is a weighted average price. These shares were purchased in multiple transactions at prices ranging from $8.4000 to $8.5600, inclusive.
3. F3. The reporting person disclaims beneficial ownership of these securities except to the extent of his pecuniary interest therein.

Key Figures

Shares purchased: 100,000 shares Weighted average purchase price: $8.3548 per share Shares purchased: 10,000 shares +3 more

6 metrics

Shares purchased 100,000 shares Direct purchase on October 13, 2026

Weighted average purchase price $8.3548 per share October 13, 2026; multiple transactions ranged from $8.2547 to $8.4616 per share

Shares purchased 10,000 shares Direct purchase on October 14, 2026

Weighted average purchase price $8.4569 per share October 14, 2026; multiple transactions ranged from $8.4000 to $8.5600 per share

Shares held by spouse 529,000 shares Indirect holding reported as of October 13, 2026

Shares held by Manatee Equity Fund LLC 187,000 shares Indirect holding reported as of October 13, 2026; Scully disclaimed beneficial ownership except to the extent of his pecuniary interest

Key Terms

weighted average price, beneficial ownership, pecuniary interest

3 terms

weighted average price financial

"The price reported in Column 4 is a weighted average price."

Weighted average price is the average price of a security where each trade or component is counted according to its size, so bigger trades pull the average more than smaller ones. Think of it like calculating the average cost of a grocery haul where items you bought more of have greater influence on the final per-item cost. Investors use it to understand the true average price paid or received, judge execution quality, and compare trading performance against market movement.

beneficial ownership regulatory

"disclaims beneficial ownership of these securities"

Beneficial ownership means the person or entity that actually enjoys the benefits of owning shares or other assets — such as receiving dividends, voting rights, or price gains — even if the legal title is held in another name. For investors it matters because knowing who truly controls and profits from a company reveals who can influence decisions, exposes potential conflicts of interest or hidden concentration of power, and affects transparency and risk in the stock.

pecuniary interest financial

"except to the extent of his pecuniary interest therein."

FAQ

AI-generated questions and answers. How Rhea-AI works. Not financial advice.

How many PRTA shares did William P. Scully buy, and at what prices?

William P. Scully directly purchased 100,000 shares on October 13, 2026, at a weighted average $8.3548 per share, and 10,000 shares on October 14, 2026, at a weighted average $8.4569 per share. The reported prices were weighted averages across multiple transactions within the stated price ranges.

AI-generated analysis. How Rhea-AI works. Not financial advice.

Form 4 Insider Transactions: What Each Field Means →

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Available on EDGAR 10/15/2026 - 04:22 PM EDT Accepted by SEC EDGAR 10/15/2026 - 04:21 PM EDT Learn about SEC filing dates

SEC Form 4

FORM 4

UNITED STATES SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP

Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934
or Section 30(h) of the Investment Company Act of 1940

OMB APPROVAL

OMB Number:			3235-0287
Estimated average burden
hours per response:			0.5

Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).

Check this box to indicate that a transaction was made pursuant to a contract, instruction or written plan for the purchase or sale of equity securities of the issuer that is intended to satisfy the affirmative defense conditions of Rule 10b5-1(c). See Instruction 10.

1. Name and Address of Reporting Person^*

SCULLY WILLIAM P

(Last) (First) (Middle)

771 MANATEE COVE

(Street)

VERO BEACH FLORIDA 32963

(City) (State) (Zip)

UNITED STATES

(Country)

2. Issuer Name and Ticker or Trading Symbol
PROTHENA CORP PUBLIC LTD CO [ PRTA ]

5. Relationship of Reporting Person(s) to Issuer
(Check all applicable)

	Director	X	10% Owner
	Officer (give title below)		Other (specify below)

2a. Foreign Trading Symbol

3. Date of Earliest Transaction (Month/Day/Year)
10/13/2026

6. Individual or Joint/Group Filing (Check Applicable Line)

X	Form filed by One Reporting Person
	Form filed by More than One Reporting Person

4. If Amendment, Date of Original Filed (Month/Day/Year)

Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned
1. Title of Security (Instr. 3)	2. Transaction Date (Month/Day/Year)	2A. Deemed Execution Date, if any (Month/Day/Year)	3. Transaction Code (Instr. 8)		4. Securities Acquired (A) or Disposed Of (D) (Instr. 3, 4 and 5)			5. Amount of Securities Beneficially Owned Following Reported Transaction(s) (Instr. 3 and 4)	6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4)	7. Nature of Indirect Beneficial Ownership (Instr. 4)
			Code	V	Amount	(A) or (D)	Price
Ordinary Shares, par value $0.01 per share	10/13/2026		P		100,000	A	$8.3548(1)	1,027,000	D
Ordinary Shares, par value $0.01 per share	10/14/2026		P		10,000	A	$8.4569(2)	1,037,000	D
Ordinary Shares, par value $0.01 per share								529,000	I	By Spouse
Ordinary Shares, par value $0.01 per share								187,000	I	By Manatee Equity Fund LLC(3)

Table II - Derivative Securities Acquired, Disposed of, or Beneficially Owned (e.g., puts, calls, warrants, options, convertible securities)
1. Title of Derivative Security (Instr. 3)	2. Conversion or Exercise Price of Derivative Security	3. Transaction Date (Month/Day/Year)	3A. Deemed Execution Date, if any (Month/Day/Year)	4. Transaction Code (Instr. 8)		5. Number of Derivative Securities Acquired (A) or Disposed of (D) (Instr. 3, 4 and 5)		6. Date Exercisable and Expiration Date (Month/Day/Year)		7. Title and Amount of Securities Underlying Derivative Security (Instr. 3 and 4)		8. Price of Derivative Security (Instr. 5)	9. Number of derivative Securities Beneficially Owned Following Reported Transaction(s) (Instr. 4)	10. Ownership Form: Direct (D) or Indirect (I) (Instr. 4)	11. Nature of Indirect Beneficial Ownership (Instr. 4)
				Code	V	(A)	(D)	Date Exercisable	Expiration Date	Title	Amount or Number of Shares

Explanation of Responses:

1. The price reported in Column 4 is a weighted average price. These shares were purchased in multiple transactions at prices ranging from $8.2547 to $8.4616, inclusive. The reporting person undertakes to provide to Prothena Corp Public Ltd Co, any security holder of Prothena Corp Public Ltd Co, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the ranges set forth in footnotes (1) and (2) to this Form 4.

2. The price reported in Column 4 is a weighted average price. These shares were purchased in multiple transactions at prices ranging from $8.4000 to $8.5600, inclusive.

3. The reporting person disclaims beneficial ownership of these securities except to the extent of his pecuniary interest therein.

	Reid E. Buchanan by POA from William P. Scully	10/15/2026
	** Signature of Reporting Person	Date
Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.
* If the form is filed by more than one reporting person, see Instruction 4 (b)(v).
** Intentional misstatements or omissions of facts constitute Federal Criminal Violations See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).
Note: File three copies of this Form, one of which must be manually signed. If space is insufficient, see Instruction 6 for procedure.
Persons who respond to the collection of information contained in this form are not required to respond unless the form displays a currently valid OMB Number.
* Form 4: SEC 1474 (03-26)