X0306 4 2023-01-18 0 0001559053 PROTHENA CORP PUBLIC LTD CO PRTA 0001457013 Nguyen Tran C/O PROTHENA BIOSCIENCES INC 331 OYSTER POINT BOULEVARD SOUTH SAN FRANCISCO CA 94080 0 1 0 0 Chief Strategy Officer and CFO Ordinary Shares, par value $0.01 per share 2023-01-18 4 M 0 10000 6.73 A 13200 D Ordinary Shares, par value $0.01 per share 2023-01-18 4 S 0 7277 55.177 D 5923 D Ordinary Shares, par value $0.01 per share 2023-01-18 4 S 0 2085 56.3242 D 3838 D Ordinary Shares, par value $0.01 per share 2023-01-18 4 S 0 638 56.9709 D 3200 D Stock Option (Right to Buy) 6.73 2023-01-18 4 M 0 10000 0 D 2023-03-31 Ordinary Shares 10000 20000 D The transactions reported in the Form 4 were effected pursuant to a Rule 10b5-1 trading plan adopted by the Reporting Person in connection with a court stipulation and proposed order regarding the separation of assets ("Court Order") in anticipation of a potential divorce settlement agreement. The transaction was executed in multiple trades in prices ranging from $54.77 to $55.755, inclusive. The price reported in Column 4 above reflects the weighted average sale price. The reporting person hereby undertakes to provide to the Securities and Exchange Commission staff, the Issuer, or a security holder of the Issuer, upon request, full information regarding the number of shares sold at each respective price within the range set forth in footnotes 2 through 4 of this Form 4. The transaction was executed in multiple trades in prices ranging from $55.78 to $56.755, inclusive. The transaction was executed in multiple trades in prices ranging from $56.815 to $57.355, inclusive. The option was granted on April 1, 2013 and all shares subject to the option were fully vested and exercisable. The option will expire in approximately two months and be forfeited to the extent it is not exercised on or prior to March 31, 2023. The Reporting Person holds options that give him the right to acquire an aggregate of 873,837 shares at exercise prices ranging from $6.73 to $32.45, of which 708,753 are currently exercisable, and 165,084 are currently unexercisable but vest over time, subject to the Reporting Person's continued employment with the Issuer on each applicable vesting date of each option award. Certain of these options are subject to the Court Order. /s/ Michael Malecek, as Attorney in Fact for Tran B. Nguyen 2023-01-20