Prothena (PRTA) COO Brandon Smith awarded stock option on 190,000 shares

Rhea-AI Filing Summary

PROTHENA CORP PUBLIC LTD CO granted Chief Operating Officer Brandon S. Smith a stock option covering 190,000 shares on March 3, 2026. This option was reported as a direct, derivative security and classified as a grant or award acquisition.

According to the vesting terms, 25% of the shares underlying the option will vest and become exercisable on March 3, 2027. The remaining shares will vest in 1/48th monthly installments on each monthly anniversary thereafter, conditioned on Smith’s continued employment with the company on each vesting date.

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

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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^*

Smith Brandon S.

(Last) (First) (Middle)

C/O PROTHENA BIOSCIENCES INC

1800 SIERRA POINT PARKWAY

(Street)

BRISBANE CA 94005

(City) (State) (Zip)

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

3. Date of Earliest Transaction (Month/Day/Year)
03/03/2026

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

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

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

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

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
Stock Option (Right to Buy)	$9.36	03/03/2026		A		190,000		(1)	03/03/2036	Ordinary Shares	190,000	$0	190,000	D

Explanation of Responses:

1. The shares subject to the option will vest and become exercisable as to 25% of the total number of shares subject to the option on March 3, 2027, and with respect to 1/48th of the total number of shares subject to the option in successive, equal monthly installments on each monthly anniversary thereafter, subject to the Reporting Person's continued employment with the Issuer on each such vesting date.

	/s/ Michael Malecek, as Attorney in Fact for Brandon S. Smith	03/05/2026
	** 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.

FAQ

What did Prothena (PRTA) report in Brandon S. Smith’s latest Form 4?

Prothena reported that Chief Operating Officer Brandon S. Smith received a stock option grant for 190,000 shares on March 3, 2026. The filing classifies this as a grant, award, or other acquisition of a derivative security held directly.

How many shares are covered by Brandon S. Smith’s new stock option at Prothena (PRTA)?

The new stock option granted to Brandon S. Smith covers 190,000 shares of Prothena common stock. After this grant, the Form 4 shows 190,000 derivative shares held following the transaction, all reported as directly owned by the executive.

When does Brandon S. Smith’s Prothena (PRTA) stock option start vesting?

The option begins vesting on March 3, 2027, when 25% of the total 190,000 shares become exercisable. The remaining portion then vests in 1/48th monthly installments on each monthly anniversary, contingent on continued employment with Prothena.

What are the ongoing vesting terms for Brandon S. Smith’s Prothena (PRTA) option grant?

After the initial 25% vests on March 3, 2027, the balance vests in 1/48th equal monthly installments. Each monthly vesting is subject to Brandon S. Smith’s continued employment with Prothena on the applicable vesting date, according to the Form 4 footnote.

Is Brandon S. Smith’s Prothena (PRTA) option grant reported as direct or indirect ownership?

The Form 4 reports the 190,000-share stock option as direct ownership. The ownership code is shown as “D,” and there is no footnote indicating that the option is held through a separate entity, trust, or other indirect structure.

What type of transaction code is used for Brandon S. Smith’s Prothena (PRTA) option grant?

The transaction uses code “A”, described as a grant, award, or other acquisition. It is classified as a derivative security transaction and marked with transaction direction “acquire,” reflecting the award of a new stock option position rather than an open-market trade.