First through Sixth Amendments to the Prothena Corporation plc 2020 Employment Inducement Incentive Plan

This First Amendment (this “First Amendment”) to the Prothena Corporation plc 2020 Employment Inducement Incentive Plan (“2020 EIIP”), was made and adopted by the Board of Directors (“Board”) of Prothena Corporation plc, a public limited company organized under the laws of Ireland (the “Company”), on April 1, 2020 (the “Amendment Date”).

WHEREAS, the Board believes it is in the best interests of the Company and its shareholders to amend the 2020 EIIP to increase the number of ordinary shares authorized for issuance under the 2020 EIIP.

NOW, THEREFORE, BE IT RESOLVED, that the 2020 EIIP is hereby amended as follows, effective as of the Amendment Date:

1.Section 2.28 of the 2020 EIIP is hereby amended and restated in its entirety as follows:

“2.28 “Overall Share Limit” means 360,000 Shares.”

2.This First Amendment shall be and hereby is incorporated into and forms a part of the 2020 EIIP, and except as expressly provided herein, all terms and conditions of the 2020 EIIP shall remain in full force and effect.

This Second Amendment (this “Second Amendment”) to the Prothena Corporation plc 2020 Employment Inducement Incentive Plan (“2020 EIIP”), was made and adopted by the Board of Directors (“Board”) of Prothena Corporation plc, a public limited company organized under the laws of Ireland (the “Company”), on July 15, 2020 (the “Amendment Date”).

WHEREAS, the Board believes it is in the best interests of the Company and its shareholders to amend the 2020 EIIP to increase the number of ordinary shares authorized for issuance under the 2020 EIIP.

NOW, THEREFORE, BE IT RESOLVED, that the 2020 EIIP is hereby amended as follows, effective as of the Amendment Date:

1.Section 2.28 of the 2020 EIIP is hereby amended and restated in its entirety as follows:

“2.28 “Overall Share Limit” means 420,000 Shares.”

2.This Second Amendment shall be and hereby is incorporated into and forms a part of the 2020 EIIP, and except as expressly provided herein, all terms and conditions of the 2020 EIIP shall remain in full force and effect.

This Third Amendment (this “Third Amendment”) to the Prothena Corporation plc 2020 Employment Inducement Incentive Plan (“2020 EIIP”), was made and adopted by the Board of Directors (“Board”) of Prothena Corporation plc, a public limited company organized under the laws of Ireland (the “Company”), on September 1, 2020 (the “Amendment Date”).

WHEREAS, the Board believes it is in the best interests of the Company and its shareholders to amend the 2020 EIIP to increase the number of ordinary shares authorized for issuance under the 2020 EIIP.

NOW, THEREFORE, BE IT RESOLVED, that the 2020 EIIP is hereby amended as follows, effective as of the Amendment Date:

1.Section 2.28 of the 2020 EIIP is hereby amended and restated in its entirety as follows:

“2.28 “Overall Share Limit” means 480,000 Shares.”

2.This Third Amendment shall be and hereby is incorporated into and forms a part of the 2020 EIIP, and except as expressly provided herein, all terms and conditions of the 2020 EIIP shall remain in full force and effect.

This Fourth Amendment (this “Fourth Amendment”) to the Prothena Corporation plc 2020 Employment Inducement Incentive Plan (“2020 EIIP”), was made and adopted by the Board of Directors (“Board”) of Prothena Corporation plc, a public limited company organized under the laws of Ireland (the “Company”), on October 1, 2020 (the “Amendment Date”).

WHEREAS, the Board believes it is in the best interests of the Company and its shareholders to amend the 2020 EIIP to increase the number of ordinary shares authorized for issuance under the 2020 EIIP.

NOW, THEREFORE, BE IT RESOLVED, that the 2020 EIIP is hereby amended as follows, effective as of the Amendment Date:

1.Section 2.28 of the 2020 EIIP is hereby amended and restated in its entirety as follows:

“2.28 “Overall Share Limit” means 530,000 Shares.”

2.This Fourth Amendment shall be and hereby is incorporated into and forms a part of the 2020 EIIP, and except as expressly provided herein, all terms and conditions of the 2020 EIIP shall remain in full force and effect.

This Fifth Amendment (this “Fifth Amendment”) to the Prothena Corporation plc 2020 Employment Inducement Incentive Plan (“2020 EIIP”), was made and adopted by the Board of Directors (“Board”) of Prothena Corporation plc, a public limited company organized under the laws of Ireland (the “Company”), on November 2, 2020 (the “Amendment Date”).

WHEREAS, the Board believes it is in the best interests of the Company and its shareholders to amend the 2020 EIIP to increase the number of ordinary shares authorized for issuance under the 2020 EIIP.

NOW, THEREFORE, BE IT RESOLVED, that the 2020 EIIP is hereby amended as follows, effective as of the Amendment Date:

1.Section 2.28 of the 2020 EIIP is hereby amended and restated in its entirety as follows:

“2.28 “Overall Share Limit” means 620,000 Shares.”

2.This Fifth Amendment shall be and hereby is incorporated into and forms a part of the 2020 EIIP, and except as expressly provided herein, all terms and conditions of the 2020 EIIP shall remain in full force and effect.

This Sixth Amendment (this “Sixth Amendment”) to the Prothena Corporation plc 2020 Employment Inducement Incentive Plan (“2020 EIIP”), was made and adopted by the Board of Directors (“Board”) of Prothena Corporation plc, a public limited company organized under the laws of Ireland (the “Company”), on December 1, 2020 (the “Amendment Date”).

WHEREAS, the Board believes it is in the best interests of the Company and its shareholders to amend the 2020 EIIP to increase the number of ordinary shares authorized for issuance under the 2020 EIIP.

NOW, THEREFORE, BE IT RESOLVED, that the 2020 EIIP is hereby amended as follows, effective as of the Amendment Date:

1.Section 2.28 of the 2020 EIIP is hereby amended and restated in its entirety as follows:

“2.28 “Overall Share Limit” means 710,000 Shares.”

2.This Sixth Amendment shall be and hereby is incorporated into and forms a part of the 2020 EIIP, and except as expressly provided herein, all terms and conditions of the 2020 EIIP shall remain in full force and effect.