X0306 4 2021-10-20 0 0001559053 PROTHENA CORP PUBLIC LTD CO PRTA 0001559422 Walker Karin L C/O PROTHENA BIOSCIENCES INC 331 OYSTER POINT BOULEVARD SOUTH SAN FRANCISCO CA 94080 0 1 0 0 Chief Accounting Officer Ordinary Shares, par value $0.01 per share 2021-10-20 4 M 0 20000 15.04 A 20000 D Ordinary Shares, par value $0.01 per share 2021-10-20 4 M 0 3000 29.81 A 23000 D Ordinary Shares, par value $0.01 per share 2021-10-20 4 S 0 19115 60.002 D 3885 D Ordinary Shares, par value $0.01 per share 2021-10-20 4 S 0 1700 60.9082 D 2185 D Ordinary Shares, par value $0.01 per share 2021-10-20 4 S 0 2185 61.9407 D 0 D Stock Option (right to buy) 15.04 2021-10-20 4 M 0 20000 0.00 D 2028-06-21 Ordinary Shares 20000 90000 D Stock Option (right to buy) 29.81 2021-10-20 4 M 0 3000 0.00 D 2024-02-04 Ordinary Shares 3000 0 D The transactions reported in the Form 4 were effected pursuant to a Rule 10b5-1 trading plan adopted by the Reporting Person. The transaction was executed in multiple trades in prices ranging from $59.71 to $60.43, 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 this footnote. The transaction was executed in multiple trades in prices ranging from $60.75 to $61.71, 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 this footnote. The transaction was executed in multiple trades in prices ranging from $61.84 to $62.22, 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 this footnote. The shares subject to the option vested and became exercisable as to 25% of the total number of shares subject to the option on June 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. 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 4, 2015, 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 or service relationship with the Issuer on each such vesting date. /s/ Michael Malecek, as Attorney in Fact for Karin L. Walker 2021-10-22