Sec Form 4 Filing - Karp Carol D. @ PROTHENA CORP PUBLIC LTD CO - 2021-02-12

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

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, Section 17(a) of the Public Utility Holding Company Act of 1935 or Section 30(h) of the Investment Company Act of 1940

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1. Name and Address of Reporting Person Karp Carol D. 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 Regulatory Officer (Last) (First) (Middle) C/O PROTHENA BIOSCIENCES INC, 331 OYSTER POINT BOULEVARD 3. Date of Earliest Transaction (MM/DD/YY) 02/12/2021 (Street) SOUTH SAN FRANCISCO, CA94080 4. If Amendment, Date Original Filed (MM/DD/YY) 6. Individual or Joint/Group Filing (Check Applicable Line) __ X __ Form filed by One Reporting Person _____ Form filed by More than One Reporting Person (City) (State) (Zip)

Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned 1.Title of Security (Instr. 3) 2. Transaction Date (MM/DD/YY) 2A. Deemed Execution Date, if any (MM/DD/YY) 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 (MM/DD/YY) 3A. Deemed Execution Date, if any (MM/DD/YY) 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 (MM/DD/YY) 7. Title and Amount of Underlying Securities (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 of Derivative Security: 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 Employee Stock Option (Right to Buy) $ 52.78 02/12/2021 D 100,000 12/14/2020 12/14/2026 Ordinary Shares 100,000 ( 1 ) 0 D Employee Stock Option (Right to Buy) $ 22.85 02/12/2021 A 51,282 ( 2 ) 12/14/2026 Ordinary Shares 51,282 ( 1 ) 51,282 D Employee Stock Option (Right to Buy) $ 33.1 02/12/2021 D 60,000 ( 3 ) 02/21/2028 Ordinary Shares 60,000 ( 4 ) 0 D Employee Stock Option (Right to Buy) $ 22.85 02/12/2021 A 45,112 ( 5 ) 02/21/2028 Ordinary Shares 45,112 ( 4 ) 45,112 D

Reporting Owners Reporting Owner Name / Address Relationships Director 10% Owner Officer Other Karp Carol D. C/O PROTHENA BIOSCIENCES INC 331 OYSTER POINT BOULEVARD SOUTH SAN FRANCISCO, CA94080 Chief Regulatory Officer Signatures /s/ Michael Malecek, as Attorney in Fact for Carol D. Karp 02/17/2021 Signature of Reporting Person Date

Explanation of Responses:

( 1 )On February 12, 2021, the issuer canceled, pursuant to the issuer's option exchange program, an option for 100,000 of the issuer's ordinary shares granted to the reporting person on December 14, 2016. In exchange, the reporting person received a replacement option, for 51,282 ordinary shares, having an exercise price of $22.85 per ordinary share. ( 2 )The shares subject to the option will vest and become exercisable on the one year anniversary of the date of grant, subject to the reporting person's continued service with the issuer through such one year anniversary. ( 3 )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 February 21, 2019 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. ( 4 )On February 12, 2021, the issuer canceled, pursuant to the issuer's option exchange program, an option for 60,000 of the issuer's ordinary shares granted to the reporting person on February 21, 2018. In exchange, the reporting person received a replacement option, for 45,112 ordinary shares, having an exercise price of $22.85 per ordinary share. ( 5 )The shares subject to the option will vest and become exercisable as to 47/48 of the total number of shares subject to the option on the one year anniversary of the date of grant and with respect to 1/48 of the total number of shares subject to the option on February 21, 2022, subject to the reporting person's continued service with the issuer on each such vesting 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).

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