Prothena fund buys 103,500 shares at $8.60 each

Prothena Corp Public Ltd Co (PRTA) ten-percent owner William P. Scully reported that Manatee Equity Fund LLC purchased 103,500 ordinary shares on September 28, 2026, at a weighted average of $8.5978 per share.

Rhea-AI Filing Summary

Prothena Corp Public Ltd Co (PRTA) ten-percent owner William P. Scully reported that Manatee Equity Fund LLC purchased 103,500 ordinary shares on September 28, 2026, at a weighted average of $8.5978 per share. The purchases occurred in multiple transactions at prices from $8.1582 to $8.8500, inclusive, and the fund held 187,000 shares afterward. Scully disclaimed beneficial ownership of the fund’s shares except to the extent of his pecuniary interest. Separately, the report lists 927,000 shares held directly and 52,000 held by his spouse.

Insider Trade Summary

Net Buyer: 103,500 shares

Net Buy 3 txns

Insider SCULLY WILLIAM P

Role 10% Owner

Bought 103,500 shs ($890K)

Type	Security	Shares	Price	Value
Purchase	Ordinary Shares, par value $0.01 per share F1, F2	103,500	$8.5978	$890K
holding	Ordinary Shares, par value $0.01 per share	--	--	--
holding	Ordinary Shares, par value $0.01 per share	--	--	--

Holdings After Transaction: Ordinary Shares, par value $0.01 per share — 187,000 shares (Indirect, By Manatee Equity Fund LLC); Ordinary Shares, par value $0.01 per share — 927,000 shares (Direct); Ordinary Shares, par value $0.01 per share — 52,000 shares (Indirect, By Spouse)

Footnotes (2)

1. F1. The price reported in Column 4 is a weighted average price. These shares were purchased in multiple transactions at prices ranging from $8.1582 to $8.8500, 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 footnote (1) to this Form 4.
2. F2. The reporting person disclaims beneficial ownership of these securities except to the extent of his pecuniary interest therein.

Key Figures

Shares purchased: 103,500 ordinary shares Weighted average purchase price: $8.5978 per share Purchase price range: $8.1582–$8.8500 per share +3 more

6 metrics

Shares purchased 103,500 ordinary shares Manatee Equity Fund LLC purchase on September 28, 2026

Weighted average purchase price $8.5978 per share Manatee Equity Fund LLC purchase on September 28, 2026

Purchase price range $8.1582–$8.8500 per share Multiple transactions; inclusive

Fund shares following purchase 187,000 ordinary shares Held by Manatee Equity Fund LLC after the September 28, 2026 purchase

Direct holdings 927,000 ordinary shares Direct holding reported on September 28, 2026

Spouse holdings 52,000 ordinary shares Held by spouse and reported on September 28, 2026

Key Terms

weighted average price, pecuniary interest, beneficial ownership

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.

pecuniary interest financial

"except to the extent of his pecuniary interest"

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.

FAQ

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

How many PRTA shares did Manatee Equity Fund LLC purchase, and at what price?

Manatee Equity Fund LLC purchased 103,500 PRTA ordinary shares on September 28, 2026, at a weighted average of $8.5978 per share. The purchases occurred in multiple transactions at prices from $8.1582 to $8.8500, inclusive; the fund held 187,000 shares afterward. No Rule 10b5-1 plan is reported.

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

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Available on EDGAR 09/29/2026 - 05:38 PM Accepted by SEC EDGAR 09/29/2026 - 05:37 PM 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)
09/28/2026

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	09/28/2026		P		103,500	A	$8.5978(1)	187,000	I	By Manatee Equity Fund LLC(2)
Ordinary Shares, par value $0.01 per share								927,000	D
Ordinary Shares, par value $0.01 per share								52,000	I	By Spouse

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 $8.1582 to $8.8500, 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 footnote (1) to this Form 4.

2. 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	09/29/2026
	** 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)