X0306 4 2019-02-27 0 0001559053 Prothena Corp plc PRTA 0001457013 Nguyen Tran C/O PROTHENA BIOSCIENCES INC 331 OYSTER POINT BOULEVARD SOUTH SAN FRANCISCO CA 94080 0 1 0 0 See Remarks Ordinary Shares, par value $0.01 per share 3200 D Stock Option (right to buy) 13.53 2019-02-27 4 A 0 95000 0.00 A 2029-02-27 Ordinary Shares 95000 95000 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 February 27, 2020 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. Chief Operating Officer and Chief Financial Officer /s/ A.W. Homan, as Attorney in Fact for Tran B. Nguyen 2019-03-01