FORM 3 UNITED STATES SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

INITIAL STATEMENT OF BENEFICIAL OWNERSHIP OF SECURITIES

Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934
or Section 30(h) of the Investment Company Act of 1940
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1. Name and Address of Reporting Person *
Isaacs Michael John
(Last) (First) (Middle)
C/O PROTHENA BIOSCIENCES INC.
1800 SIERRA POINT PARKWAY
(Street)
BRISBANE CA 94005
(City) (State) (Zip)
2. Date of Event Requiring Statement (Month/Day/Year)
06/08/2026 		3. Issuer Name and Ticker or Trading Symbol
PROTHENA CORP PUBLIC LTD CO [ PRTA ]
4. Relationship of Reporting Person(s) to Issuer
(Check all applicable)
Director 10% Owner
X Officer (give title below) Other (specify below)
General Counsel & Company Sec.
 5. 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 Beneficially Owned
1. Title of Security (Instr. 4) 2. Amount of Securities Beneficially Owned (Instr. 4) 3. Ownership Form: Direct (D) or Indirect (I) (Instr. 5) 4. Nature of Indirect Beneficial Ownership (Instr. 5)
Ordinary Shares, par value $0.01 per share 48,825
D
 
Table II - Derivative Securities Beneficially Owned
(e.g., puts, calls, warrants, options, convertible securities)
1. Title of Derivative Security (Instr. 4) 2. Date Exercisable and Expiration Date (Month/Day/Year) 3. Title and Amount of Securities Underlying Derivative Security (Instr. 4) 4. Conversion or Exercise Price of Derivative Security 5. Ownership Form: Direct (D) or Indirect (I) (Instr. 5) 6. Nature of Indirect Beneficial Ownership (Instr. 5)
Date Exercisable Expiration Date Title Amount or Number of Shares
Stock Option (Right to Buy)   (1) 04/01/2030 Ordinary Shares 17,500 10.99 D  
Stock Option (Right to Buy)   (1) 02/25/2031 Ordinary Shares 10,000 22.6 D  
Stock Option (Right to Buy)   (1) 02/23/2032 Ordinary Shares 8,250 32.45 D  
Stock Option (Right to Buy)   (2) 03/02/2033 Ordinary Shares 8,800 52.97 D  
Stock Option (Right to Buy)   (3) 02/27/2034 Ordinary Shares 12,000 30.3 D  
Stock Option (Right to Buy)   (4) 03/05/2035 Ordinary Shares 8,612 14.95 D  
Stock Option (Right to Buy)   (5) 03/03/2036 Ordinary Shares 37,500 9.36 D  
Stock Option (Right to Buy)   (6) 04/10/2036 Ordinary Shares 50,000 10.5 D  
Explanation of Responses:
1. The option is fully vested.
2. The shares subject to the option vested and became exercisable as to 25% of the total number of shares subject to the option on March 2, 2024, and vest and become exercisable 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.
3. The shares subject to the option vested and became exercisable as to 25% of the total number of shares subject to the option on February 27, 2025, and vest and become exercisable 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.
4. The shares subject to the option vested and became exercisable as to 25% of the total number of shares subject to the option on March 5, 2026, and vest and become exercisable 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.
5. 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.
6. 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 April 10, 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.
Remarks:
Exhibit List: Exhibit 24 - Power of Attorney
/s/ Michael J. Isaacs 06/12/2026
** 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.
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POWER OF ATTORNEY