X0306 4 2018-06-21 0 0001559053 Prothena Corp plc PRTA 0001708681 Zago Wagner M. C/O PROTHENA BIOSCIENCES INC 331 OYSTER POINT BOULEVARD SOUTH SAN FRANCISCO CA 94080 0 1 0 0 Chief Scientific Officer Stock Option (right to buy) 15.04 2018-06-21 4 A 0 150000 0.00 A 2028-06-21 Ordinary Shares 150000 150000 D 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 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. /s/ A.W. Homan, as Attorney-in-Fact for Wagner M. Zago 2018-06-25