PRTA / Prothena Corporation plc - Pengajuan SECLaporan Tahunan, Pernyataan Proksi

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): August 27, 2025 PROTHENA CORPORAT

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): August 27, 2025 PROTHENA CORPORATION PUBLIC LIMITED COMPANY (Exact name of registrant as specified in its charter) Ireland 001-35676 98-1111119 (State or other jurisdiction of incorpo

Prothena Provides Update on PRX012 and Announces Results from the Phase 1 ASCENT Clinical Program

EX-99.1 Exhibit 99.1 PRESS RELEASE Prothena Provides Update on PRX012 and Announces Results from the Phase 1 ASCENT Clinical Program • As previously communicated, Prothena plans to explore potential partnership interest to advance PRX012 and its preclinical PRX012-TfR (transferrin receptor) antibody • Phase 1 ASCENT clinical program established proof-of-mechanism for PRX012 as a once-monthly, subc

Calculation of Filing Fee Tables Form S-8 (Form Type) Prothena Corporation Public Limited Company (Exact Name of Registrant as Specified in its Charter) Table 1: Newly Registered Securities

Exhibit 107 Calculation of Filing Fee Tables Form S-8 (Form Type) Prothena Corporation Public Limited Company (Exact Name of Registrant as Specified in its Charter) Table 1: Newly Registered Securities Security Type Security Class Title Fee Calculation Rule Amount Registered Proposed Maximum Offering Price Per Unit Maximum Aggregate Offering Price Fee Rate Amount of Registration Fee 1 Equity Ordinary Shares, par value $0.

As filed with the Securities and Exchange Commission on August 8, 2025

As filed with the Securities and Exchange Commission on August 8, 2025 Registration No.

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): August 6, 2025 PROTHENA CORPORATI

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): August 6, 2025 PROTHENA CORPORATION PUBLIC LIMITED COMPANY (Exact name of registrant as specified in its charter) Ireland 001-35676 98-1111119 (State or other jurisdiction of incorpor

Prothena Announces that Novo Nordisk Will Advance Coramitug (formerly PRX004) into Phase 3 Development for ATTR Amyloidosis with Cardiomyopathy

EX-99.1 Exhibit 99.1 PRESS RELEASE Prothena Announces that Novo Nordisk Will Advance Coramitug (formerly PRX004) into Phase 3 Development for ATTR Amyloidosis with Cardiomyopathy • Coramitug is a potential first-in-class amyloid depleter antibody for the treatment of ATTR amyloidosis with cardiomyopathy1-3 • Novo Nordisk successfully completed a Phase 2 trial with coramitug and is expected to init

June 30, December 31, 2025 2024 Assets Cash and cash equivalents $ 371,435 $ 471,388 Prepaid expenses and other current assets 14,040 14,024 Total current assets 385,475 485,412 Property and equipment, net 2,690 3,081 Operating lease right-of-use ass

Exhibit 99.1 PRESS RELEASE Prothena Reports Second Quarter 2025 Financial Results and Business Highlights •Net cash used in operating and investing activities was $46.4 million in the second quarter and net cash used in operating and investing activities was $99.8 million for the first six months of 2025; quarter-end cash and restricted cash position was $372.3 million •Prothena expects to convene

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-Q

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-Q (Mark One) ☒ QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the quarterly period ended June 30, 2025 Or ☐ TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 Commission file number: 001-35676 PROTHENA CORPORATION PUBLIC LIMITED COMPANY

Award Agreement between Prothena Corporation plc and its Named Executive Officers under the Prothena Corporation plc 2018 Long Term Incentive Plan

Form of Restricted Share Unit Award Agreement between Prothena Corporation plc and Registrant’s Named Executive Officers PROTHENA CORPORATION PLC 2018 LONG TERM INCENTIVE PLAN Restricted Share Unit Award Agreement – Cover Sheet Prothena Corporation plc, an Irish public limited company (the “Company”), hereby grants a Restricted Share Unit Award with respect to Shares to the individual named below.

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): August 4, 2025 PROTHENA CORPORATI

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): August 4, 2025 PROTHENA CORPORATION PUBLIC LIMITED COMPANY (Exact name of registrant as specified in its charter) Ireland 001-35676 98-1111119 (State or Other Jurisdiction of Incorpor

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): July 30, 2025 PROTHENA CORPORATIO

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): July 30, 2025 PROTHENA CORPORATION PUBLIC LIMITED COMPANY (Exact name of registrant as specified in its charter) Ireland 001-35676 98-1111119 (State or other jurisdiction of incorpora

Form of Employment Agreement

EX-10.1 Exhibit 10.1 Form of Employment Agreement This Employment Agreement (the “Agreement”), dated as of [•], is made by and between Prothena Biosciences Inc, a Delaware corporation (the “Company”), and [•] (“Executive” and, together with the Company, the “Parties”) effective as of [•] (the “Effective Date”). RECITALS WHEREAS, the Company desires to assure itself of the continued services of Exe

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): June 13, 2025 PROTHENA CORPORATIO

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): June 13, 2025 PROTHENA CORPORATION PUBLIC LIMITED COMPANY (Exact name of registrant as specified in its charter) Ireland 001-35676 98-1111119 (State or other jurisdiction of incorpora

Current Report

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): June 15, 2025 PROTHENA CORPORATION PUBLIC LIMITED COMPANY (Exact name of registrant as specified in its charter) Ireland 001-35676 98-1111119 (State or other jurisdiction of incorpora

Prothena’s Partner Roche to Advance Prasinezumab into Phase III Development for Early-Stage Parkinson’s Disease

Exhibit 99.1 PRESS RELEASE Prothena’s Partner Roche to Advance Prasinezumab into Phase III Development for Early-Stage Parkinson’s Disease • Data from Phase IIb PADOVA study and longer term follow-up data suggest clinical benefit on top of symptomatic treatment in early-stage Parkinson’s disease • Prasinezumab is a potential first-in-class anti-alpha-synuclein antibody, targeting a known biologica

Prothena Announces Phase 3

Exhibit 99.1 PRESS RELEASE Prothena Announces Phase 3 AFFIRM-AL Clinical Trial for Birtamimab in Patients with AL Amyloidosis Did Not Meet Primary Endpoint • Birtamimab did not meet the primary endpoint of time to all-cause mortality or the secondary endpoints • Birtamimab development will be discontinued, including stopping the open label extension of the AFFIRM-AL clinical trial • Company will d

Current Report

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): May 23, 2025 PROTHENA CORPORATION PUBLIC LIMITED COMPANY (Exact name of registrant as specified in its charter) Ireland 001-35676 98-1111119 (State or other jurisdiction of incorporat

Amendment to the Prothena Corporation plc 2018 Long Term Incentive Plan

Exhibit 10.1 SIXTH AMENDMENT TO THE PROTHENA CORPORATION PLC 2018 LONG TERM INCENTIVE PLAN This Sixth Amendment (this “Sixth Amendment”) to the Prothena Corporation plc 2018 Long Term Incentive Plan, as amended (“2018 LTIP”), 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 Februar

Departure of Directors or Certain Officers; Election of Directors; Appointment of Certain Officers; Compensatory Arrangements of Certain Officers, Financial Statements and Exhibits, Submission of Matters to a Vote of Security Holders

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): May 13, 2025 PROTHENA CORPORATION PUBLIC LIMITED COMPANY (Exact name of registrant as specified in its charter) Ireland 001-35676 98-1111119 (State or Other Jurisdiction of Incorporat

March 31, December 31, 2025 2024 Assets Cash and cash equivalents $ 417,935 $ 471,388 Prepaid expenses and other current assets 18,238 14,024 Total current assets 436,173 485,412 Property and equipment, net 2,871 3,081 Operating lease right-of-use as

Exhibit 99.1 PRESS RELEASE Prothena Reports First Quarter 2025 Financial Results and Business Highlights •Net cash used in operating and investing activities was $53.4 million in the first quarter of 2025; quarter-end cash and restricted cash position was $418.8 million •Topline results expected in 2Q 2025 from the confirmatory Phase 3 AFFIRM-AL clinical trial of birtamimab in patients with Mayo S

Financial Statements and Exhibits, Results of Operations and Financial Condition

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): May 8, 2025 PROTHENA CORPORATION PUBLIC LIMITED COMPANY (Exact name of registrant as specified in its charter) Ireland 001-35676 98-1111119 (State or Other Jurisdiction of Incorporati

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-Q

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-Q (Mark One) ☒ QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the quarterly period ended March 31, 2025 Or ☐ TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 Commission file number: 001-35676 PROTHENA CORPORATION PUBLIC LIMITED COMPANY

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 14A Proxy Statement Pursuant to Section 14(a) of the Securities Exchange Act of 1934

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 14A Proxy Statement Pursuant to Section 14(a) of the Securities Exchange Act of 1934 Filed by the Registrant ☒ Filed by a Party other than the Registrant ☐ Check the appropriate box: ☐ Preliminary Proxy Statement ☐ Confidential, for Use of the Commission Only (as permitted by Rule 14a-6(e)(2)) ☐ Definitive Proxy State

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 14A Proxy Statement Pursuant to Section 14(a) of the Securities Exchange Act of 1934

TABLE OF CONTENTS UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 14A Proxy Statement Pursuant to Section 14(a) of the Securities Exchange Act of 1934 Filed by the Registrant ☒ Filed by a Party other than the Registrant ☐ Check the appropriate box: ☐ Preliminary Proxy Statement ☐ Confidential, for Use of the Commission Only (as permitted by Rule 14a-6(e)(2)) ☒ Defi

List of Subsidiaries

Exhibit 21.1 List of Subsidiaries Subsidiary Name Jurisdiction of Incorporation or Organization Prothena Biosciences Limited Ireland Prothena Biosciences Inc Delaware Prothena Finance Inc Delaware Othair Prothena Limited Ireland Prothena Pharma Limited Ireland Prothena Platform Technologies Limited Ireland

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-K

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-K (Mark One) ☒ ANNUAL REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the year ended December 31, 2024 ☐ TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the transition period from to Commission file number: 001-35676 PROTHENA CORPORATION PUB

Description of Registrant’s Securities

EXHIBIT 4.2 DESCRIPTION OF REGISTRANT’S SECURITIES This description is summarized from, and qualified in its entirety by reference to, our Amended and Restated Memorandum and Articles of Association (our “Constitution”), each of which are incorporated by reference as exhibits to the Annual Report on Form 10-K of which this exhibit is a part. In this exhibit, unless the context otherwise requires,

First through Fifth Amendments to the Prothena Corporation plc 2018 Long Term Incentive Plan

Exhibit 10.11(b) FIRST AMENDMENT TO THE PROTHENA CORPORATION PLC 2018 LONG TERM INCENTIVE PLAN This First Amendment (this “First Amendment”) to the Prothena Corporation plc 2018 Long Term Incentive Plan (“2018 LTIP”), 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 February 25, 20

Corporation plc Insider Trading Compliance Policy

Exhibit 19.1 PROTHENA CORPORATION PLC INSIDER TRADING COMPLIANCE POLICY I. PURPOSE It is illegal for any employee, officer or director of Prothena Corporation plc or any of its subsidiaries (the “Company”) to trade in the securities of Prothena Corporation plc while in the possession of material non-public information about the Company. A “trade” as referenced in this Insider Trading Compliance Po

December 31, 2024 2023 Assets Cash and cash equivalents $ 471,388 $ 618,830 Restricted cash, current — 1,352 Prepaid expenses and other current assets 14,024 19,100 Total current assets 485,412 639,282 Property and equipment, net 3,081 3,836 Operatin

Exhibit 99.1 PRESS RELEASE Prothena Reports Fourth Quarter and Full Year 2024 Financial Results, and Provides Financial Guidance and Business Highlights •Net cash used in operating and investing activities was $47.8 million in the fourth quarter and $150.3 million for the full year of 2024; quarter-end cash and restricted cash position was $472.2 million •The company expects cash guidance for the

Financial Statements and Exhibits, Results of Operations and Financial Condition

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): February 20, 2025 PROTHENA CORPORATION PUBLIC LIMITED COMPANY (Exact name of registrant as specified in its charter) Ireland 001-35676 98-1111119 (State or Other Jurisdiction of Incor

JOINT FILING AGREEMENT

JOINT FILING AGREEMENT The undersigned hereby agree that this Schedule 13G (the “Schedule 13G”) with respect to the common stock of Prothena Corporation Public Limited Company is, and any additional amendment thereto signed by each of the undersigned shall be, filed on behalf of each undersigned pursuant to and in accordance with the provisions of 13d-1(k) under the Securities Exchange Act of 1934, as amended, and that all subsequent amendments to the Schedule 13G shall be filed on behalf of each of the undersigned without the necessity of filing additional joint filing agreements.

AGREEMENT REGARDING JOINT FILING OF STATEMENT ON SCHEDULE 13D OR 13G

EXHIBIT 99.1 AGREEMENT REGARDING JOINT FILING OF STATEMENT ON SCHEDULE 13D OR 13G The undersigned agree to file jointly with the Securities and Exchange Commission (the “SEC”) any and all statements on Schedule 13D or Schedule 13G or Forms 3, 4 or 5(and any amendments or supplements thereto) required under section 13(d) and 16(a) of the Securities Exchange Act of 1934, as amended, in connection wi

Current Report

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): December 29, 2024 PROTHENA CORPORATION PUBLIC LIMITED COMPANY (Exact name of registrant as specified in its charter) Ireland 001-35676 98-1111119 (State or Other Jurisdiction of Incor

PRTA / Prothena Corporation plc / Fennell Todd W. - SC 13G/A Passive Investment

SC 13G/A 1 d853303dsc13ga.htm SC 13G/A UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 13G/A Under the Securities Exchange Act of 1934 (Amendment No. 1) * Prothena Corporation PLC (Name of Issuer) Ordinary Shares, $0.01 par value (Title of Class of Securities) G72800108 (CUSIP Number) Diana L. Hayes, Esq. Trenam Law 2700 Bank of America Plaza Tampa, Florida 33602 8

PRTA / Prothena Corporation plc / SCULLY WILLIAM P - SC 13G/A Passive Investment

SC 13G/A 1 d853309dsc13ga.htm SC 13G/A UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 13G/A Under the Securities Exchange Act of 1934 (Amendment No. 1) * Prothena Corporation PLC (Name of Issuer) Ordinary Shares, $0.01 par value (Title of Class of Securities) G72800108 (CUSIP Number) Diana L. Hayes, Esq. Trenam Law 2700 Bank of America Plaza Tampa, Florida 33602 8

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-Q

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-Q (Mark One) ☒ QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the quarterly period ended September 30, 2024 Or ☐ TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 Commission file number: 001-35676 PROTHENA CORPORATION PUBLIC LIMITED COM

, between Prothena Biosciences Inc and

Chad J. Swanson, Ph.D. September 27, 2024 Dear Chad: I am pleased to confirm your promotion and appointment as Chief Development Officer by the Board of Directors of Prothena Corporation plc (“Prothena” or the “Company”). In this position, you will report to Gene Kinney (President and CEO), although your duties, title and reporting relationship may change, based on the Company’s needs and prioriti

, between Prothena Biosciences Inc and Dennis J. Selkoe

Exhibit 10.1 CONSULTING AGREEMENT This Consulting Agreement (this “Agreement”) is effective as of October 1, 2024 (the “Effective Date”) and is made by and between Dennis J. Selkoe, M.D., an individual (“Consultant”), and Prothena Biosciences Inc, a Delaware corporation with offices at 1800 Sierra Point Parkway, Brisbane, CA 94005, U.S.A. (“Prothena”). Consultant and Prothena may each be referred

Three Months Ended September 30,

Exhibit 99.1 PRESS RELEASE Prothena Reports Third Quarter 2024 Financial Results and Business Highlights •Net cash used in operating and investing activities was $102.5 million and $102.5 million for the third quarter and first nine months of 2024, respectively; quarter-end cash and restricted cash position was $520.1 million •PRX012, a potential single-injection once-monthly subcutaneous treatmen

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): November 12, 2024 PROTHENA CORPOR

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): November 12, 2024 PROTHENA CORPORATION PUBLIC LIMITED COMPANY (Exact name of registrant as specified in its charter) Ireland 001-35676 98-1111119 (State or Other Jurisdiction of Incor

JOINT FILING AGREEMENT

JOINT FILING AGREEMENT The undersigned hereby agree that this Schedule 13G (the “Schedule 13G”) with respect to the common stock of Prothena Corporation Public Limited Company is, and any additional amendment thereto signed by each of the undersigned shall be, filed on behalf of each undersigned pursuant to and in accordance with the provisions of 13d-1(k) under the Securities Exchange Act of 1934, as amended, and that all subsequent amendments to the Schedule 13G shall be filed on behalf of each of the undersigned without the necessity of filing additional joint filing agreements.

PRTA / Prothena Corporation plc / WELLINGTON MANAGEMENT GROUP LLP - SEC SCHEDULE 13G Passive Investment

SC 13G 1 SEC13GFiling.htm SEC SCHEDULE 13G UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 13G Under the Securities Exchange Act of 1934 (Amendment No. )* Prothena Corporation Public Limited Company (Name of Issuer) Ordinary Shares (Title of Class of Securities) G72800108 (CUSIP Number) September 30, 2024 (Date of Event Which Requires Filing of this Statement) Chec

JOINT FILING AGREEMENT

JOINT FILING AGREEMENT The undersigned hereby agree that this Schedule 13G (the “Schedule 13G”) with respect to the common stock of Prothena Corporation Public Limited Company is, and any additional amendment thereto signed by each of the undersigned shall be, filed on behalf of each undersigned pursuant to and in accordance with the provisions of 13d-1(k) under the Securities Exchange Act of 1934, as amended, and that all subsequent amendments to the Schedule 13G shall be filed on behalf of each of the undersigned without the necessity of filing additional joint filing agreements.

PRTA / Prothena Corporation plc / WELLINGTON MANAGEMENT GROUP LLP - SEC SCHEDULE 13G Passive Investment

SC 13G/A 1 SEC13GFiling.htm SEC SCHEDULE 13G UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 13G Under the Securities Exchange Act of 1934 (Amendment No. 1 )* Prothena Corporation Public Limited Company (Name of Issuer) Ordinary Shares (Title of Class of Securities) G72800108 (CUSIP Number) October 31, 2024 (Date of Event Which Requires Filing of this Statement) Ch

PRTA / Prothena Corporation plc / STATE STREET CORP Passive Investment

SC 13G/A 1 ProthenaCorpPLC.htm SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 13G Under the Securities Exchange Act of 1934 (Amendment No. )* PROTHENA CORP PLC (Name of Issuer) COMMON STOCK (Title of Class of Securities) G72800108 (CUSIP Number) September 30, 2024 (Date of Event Which Requires Filing of This Statement) Check the appropriate box to designate the rule pursuant to

Prothena Announces Leadership Team Updates

Exhibit 99.1 PRESS RELEASE Prothena Announces Leadership Team Updates •Chad J. Swanson, Ph.D., appointed Chief Development Officer and will lead clinical development and medical functions •Hideki Garren, MD, Ph.D., Chief Medical Officer, will pursue an opportunity at a large pharmaceutical company to lead a global product development division DUBLIN, Ireland, September 27, 2024 - Prothena Corporat

Regulation FD Disclosure, Departure of Directors or Certain Officers; Election of Directors; Appointment of Certain Officers; Compensatory Arrangements of Certain Officers, Financial Statements and Exhibits

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): September 23, 2024 PROTHENA CORPORATION PUBLIC LIMITED COMPANY (Exact name of registrant as specified in its charter) Ireland 001-35676 98-1111119 (State or Other Jurisdiction of Inco

June 30, December 31, 2024 2023 Assets Cash and cash equivalents $ 564,124 $ 618,830 Restricted cash, current — 1,352 Prepaid expenses and other current assets 21,854 19,100 Total current assets 585,978 639,282 Property and equipment, net 3,486 3,836

Exhibit 99.1 PRESS RELEASE Prothena Reports Second Quarter 2024 Financial Results and Business Highlights •Net cash provided by operating and investing activities was $15.8 million in the second quarter and net cash used by operating and investing activities was $57.3 million for the first six months of 2024; quarter-end cash and restricted cash position was $565.0 million •Revised year-end cash g

As filed with the Securities and Exchange Commission on August 8, 2024

As filed with the Securities and Exchange Commission on August 8, 2024 Registration No.

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-Q

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-Q (Mark One) ☒ QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the quarterly period ended June 30, 2024 Or ☐ TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 Commission file number: 001-35676 PROTHENA CORPORATION PUBLIC LIMITED COMPANY

Financial Statements and Exhibits, Results of Operations and Financial Condition

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): August 8, 2024 PROTHENA CORPORATION PUBLIC LIMITED COMPANY (Exact name of registrant as specified in its charter) Ireland 001-35676 98-1111119 (State or Other Jurisdiction of Incorpor

Calculation of Filing Fee Table.

Exhibit 107 Calculation of Filing Fee Tables Form S-8 (Form Type) Prothena Corporation Public Limited Company (Exact Name of Registrant as Specified in its Charter) Table 1: Newly Registered Securities Security Type Security Class Title Fee Calculation Rule Amount Registered(1) Proposed Maximum Offering Price Per Unit Maximum Aggregate Offering Price Fee Rate Amount of Registration Fee Equity(2) Ordinary Shares, par value $0.

, by and between Prothena Biosciences Limited and Celgene Switzerland LLC

Exhibit 10.3 CERTAIN CONFIDENTIAL INFORMATION CONTAINED IN THIS DOCUMENT, MARKED BY [***], HAS BEEN OMITTED BECAUSE IT IS BOTH (I) NOT MATERIAL AND (II) IS THE TYPE THAT THE REGISTRANT TREATS AS PRIVATE OR CONFIDENTIAL. GLOBAL LICENSE AGREEMENT by and among PROTHENA BIOSCIENCES LIMITED and CELGENE SWITZERLAND LLC Dated as of May 24, 2024 DB1/ 145706242.22 LIST OF SCHEDULES SCHEDULE 1.32 ENABLED AN

Entry into a Material Definitive Agreement, Other Events

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): May 24, 2024 PROTHENA CORPORATION PUBLIC LIMITED COMPANY (Exact name of registrant as specified in its charter) Ireland 001-35676 98-1111119 (State or Other Jurisdiction of Incorporat

Fifth Amendment to the Prothena Corporation plc 2018 Long Term Incentive Plan

Exhibit 10.1 FIFTH AMENDMENT TO THE PROTHENA CORPORATION PLC 2018 LONG TERM INCENTIVE PLAN This Fifth Amendment (this “Fifth Amendment”) to the Prothena Corporation plc 2018 Long Term Incentive Plan, as amended (“2018 LTIP”), 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 Februar

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): May 14, 2024 PROTHENA CORPORATION

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): May 14, 2024 PROTHENA CORPORATION PUBLIC LIMITED COMPANY (Exact name of registrant as specified in its charter) Ireland 001-35676 98-1111119 (State or Other Jurisdiction of Incorporat

March 31, December 31, 2024 2023 Assets Cash and cash equivalents $ 546,512 $ 618,830 Restricted cash, current 1,352 1,352 Prepaid expenses and other current assets 18,004 19,100 Total current assets 565,868 639,282 Property and equipment, net 3,672

Exhibit 99.1 PRESS RELEASE Prothena Reports First Quarter 2024 Financial Results and Business Highlights •Net cash used in operating and investing activities was $73.2 million in the first quarter of 2024; quarter-end cash and restricted cash position was $548.7 million •Advanced potential best-in-class Alzheimer’s disease portfolio: initial data supportive of ongoing Phase 1 clinical trial for PR

Financial Statements and Exhibits, Results of Operations and Financial Condition

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): May 8, 2024 PROTHENA CORPORATION PUBLIC LIMITED COMPANY (Exact name of registrant as specified in its charter) Ireland 001-35676 98-1111119 (State or Other Jurisdiction of Incorporati

Offer letter, dated February 12, 2024, between Prothena Biosciences Inc and David A. Ford

Exhibit 10.1 David Ford February 12, 2024 Dear David: I am pleased to confirm this offer for you to join Prothena Biosciences Inc (“Prothena” or the “Company”). We are confident in your knowledge, expertise and judgment, and believe your performance will meet our team’s high-quality objectives and standards. Your start date will be March 1, 2024, and, subject to the discretion of the Prothena Corp

Side Letters to Master Collaboration Agreement, dated as of March 20, 2018, between Prothena Biosciences Limited and Celgene Switzerland LLC

Exhibit 10.1 CERTAIN CONFIDENTIAL INFORMATION CONTAINED IN THIS DOCUMENT, MARKED BY [***], HAS BEEN OMITTED BECAUSE IT IS BOTH (I) NOT MATERIAL AND (II) IS THE TYPE THAT THE REGISTRANT TREATS AS PRIVATE OR CONFIDENTIAL. Bristol Myers Squibb PO. Box 4000, Route 206 & Province Line Road, Princeton, NJ 08543-4000 SENT BY EMAIL AS PDF January 16, 2024 Prothena Biosciences Limited 77 Sir John Rogerson’

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-Q

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-Q (Mark One) ☒ QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the quarterly period ended March 31, 2024 Or ☐ TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 Commission file number: 001-35676 PROTHENA CORPORATION PUBLIC LIMITED COMPANY

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 14A Proxy Statement Pursuant to Section 14(a) of the Securities Exchange Act of 1934

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 14A Proxy Statement Pursuant to Section 14(a) of the Securities Exchange Act of 1934 Filed by the Registrant ☒ Filed by a Party other than the Registrant ☐ Check the appropriate box: ☐ Preliminary Proxy Statement ☐ Confidential, for Use of the Commission Only (as permitted by Rule 14a-6(e)(2)) ☐ Definitive Proxy State

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 14A Proxy Statement Pursuant to Section 14(a) of the Securities Exchange Act of 1934

TABLE OF CONTENTS UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 14A Proxy Statement Pursuant to Section 14(a) of the Securities Exchange Act of 1934 Filed by the Registrant ☒ Filed by a Party other than the Registrant ☐ Check the appropriate box: ☐ Preliminary Proxy Statement ☐ Confidential, for Use of the Commission Only (as permitted by Rule 14a-6(e)(2)) ☒ Defi

n Recoupment of Incentive Compensation

Exhibit 97 PROTHENA CORPORATION PLC POLICY ON RECOUPMENT OF INCENTIVE COMPENSATION Introduction The Board of Directors (the “Board”) of Prothena Corporation plc (the “Company”) has adopted this Policy on Recoupment of Incentive Compensation (this “Policy”), which provides for the recoupment of compensation in certain circumstances in the event of a restatement of financial results by the Company.

Amendment, dated February 22, 2024, to Equity Distribution Agreement.

Exhibit 1.3 PROTHENA CORPORATION PLC AMENDMENT LETTER TO EQUITY DISTRIBUTION AGREEMENT February 22, 2024 PIPER SANDLER & CO. U.S. Bancorp Center 800 Nicollet Mall Minneapolis, Minnesota 55402 STIFEL, NICOLAUS & COMPANY, INCORPORATED One South Street, 15th Floor Baltimore, Maryland 21202 CANTOR FITZGERALD & CO. 110 East 59th Street, 6th Floor New York, New York 10022 RBC CAPITAL MARKETS, LLC 200 Ve

As filed with the Securities and Exchange Commission on February 22, 2024

Table of Contents As filed with the Securities and Exchange Commission on February 22, 2024 Registration No.

Amendments to the Prothena Corporation plc 2020 Employment Inducement Incentive Plan

Exhibit 10.23 FIRST AMENDMENT 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”

List of Subsidiaries

Exhibit 21.1 List of Subsidiaries Subsidiary Name Jurisdiction of Incorporation or Organization Prothena Biosciences Limited Ireland Prothena Biosciences Inc Delaware Prothena Finance Inc Delaware Othair Prothena Limited Ireland Prothena Pharma Limited Ireland Prothena Platform Technologies Limited Ireland

Calculation of Filing Fee Table.

Exhibit 107 Calculation of Filing Fee Tables Form S-3ASR (Form Type) Prothena Corporation Public Limited Company (Exact Name of Registrant as Specified in its Charter) Table 1: Newly Registered and Carry Forward Securities Security Type Security Class Title Fee Calculation or Carry Forward Rule Amount Registered Proposed Maximum Offering Price Per Unit Maximum Aggregate Offering Price Fee Rate Amount of Registration Fee Carry Forward Form Type Carry Forward File Number Carry Forward Initial effective date Filing Fee Previously Paid In Connection with Unsold Securities to be Carried Forward Newly Registered Securities Fees to Be Paid Equity  Ordinary Shares,  par value $0.

Exhibit 4.2

EXHIBIT 4.2 DESCRIPTION OF REGISTRANT’S SECURITIES This description is summarized from, and qualified in its entirety by reference to, our Amended and Restated Memorandum and Articles of Association (our “Constitution”), each of which are incorporated by reference as exhibits to the Annual Report on Form 10-K of which this exhibit is a part. In this exhibit, unless the context otherwise requires,

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-K

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-K (Mark One) ☒ ANNUAL REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the year ended December 31, 2023 ☐ TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the transition period from to Commission file number: 001-35676 PROTHENA CORPORATION PUB

Departure of Directors or Certain Officers; Election of Directors; Appointment of Certain Officers; Compensatory Arrangements of Certain Officers

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): February 21, 2024 PROTHENA CORPORATION PUBLIC LIMITED COMPANY (Exact name of registrant as specified in its charter) Ireland 001-35676 98-1111119 (State or Other Jurisdiction of Incor

Financial Statements and Exhibits, Results of Operations and Financial Condition

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): February 15, 2024 PROTHENA CORPORATION PUBLIC LIMITED COMPANY (Exact name of registrant as specified in its charter) Ireland 001-35676 98-1111119 (State or Other Jurisdiction of Incor

December 31, 2023 2022 Assets Cash and cash equivalents $ 618,830 $ 710,406 Restricted cash, current 1,352 — Prepaid expenses and other current assets 19,100 8,692 Total current assets 639,282 719,098 Property and equipment, net 3,836 1,731 Operating

Exhibit 99.1 PRESS RELEASE Prothena Reports Fourth Quarter and Full Year 2023 Financial Results, and Provides Financial Guidance and Business Highlights •Net cash used in operating and investing activities was $52.6 million in the fourth quarter and $136.7 million for the full year of 2023; quarter-end cash and restricted cash position was $621.0 million •The company expects cash guidance for the

LIMITED POWER OF ATTORNEY

EX-99.A CUSIP No. G72800108 Schedule 13G Page 7 of 7 Pages EXHIBIT A LIMITED POWER OF ATTORNEY This Limited Power of Attorney (the “Power of Attorney”) is made and effective February 13, 2024, by and between Diana L. Hayes (the “Attorney”), an attorney and member in good standing of the Florida Bar of the State of Florida, whose principal office is located at 101 East Kennedy Boulevard, Suite 2700

PRTA / Prothena Corporation plc / SCULLY WILLIAM P - SC 13G Passive Investment

SC 13G UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 13G Under the Securities Exchange Act of 1934 (Amendment No. ) * Prothena Corporation PLC (Name of Issuer) Ordinary Shares, $0.01 par value (Title of Class of Securities) G72800108 (CUSIP Number) Diana L. Hayes, Esq. Trenam Law 2700 Bank of America Plaza Tampa, Florida 33602 813-227-7433 (Name, Address and Tele

PRTA / Prothena Corporation plc / Fennell Todd W. - SC 13G Passive Investment

SC 13G UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 13G Under the Securities Exchange Act of 1934 (Amendment No. ) * Prothena Corporation PLC (Name of Issuer) Ordinary Shares, $0.01 par value (Title of Class of Securities) G72800108 (CUSIP Number) Diana L. Hayes, Esq. Trenam Law 2700 Bank of America Plaza Tampa, Florida 33602 813-227-7433 (Name, Address and Tele

PRTA / Prothena Corporation plc / Avidity Partners Management LP Passive Investment

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, DC 20549 SCHEDULE 13G Under the Securities Exchange Act of 1934 (Amendment No.

Prothena Provides Updates on PRX012, PRX123, Birtamimab and Portfolio Programs

EX-99.1 Exhibit 99.1 PRESS RELEASE Prothena Provides Updates on PRX012, PRX123, Birtamimab and Portfolio Programs • Updates on PRX012 and PRX123 for treatment of Alzheimer’s disease, and on birtamimab for treatment of AL amyloidosis • Remain on track with partnered programs: Bristol Myers Squibb (BMS-986446 for the treatment of Alzheimer’s disease), Roche (Prasinezumab for the treatment of Parkins

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): January 8, 2024 PROTHENA CORPORAT

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): January 8, 2024 PROTHENA CORPORATION PUBLIC LIMITED COMPANY (Exact name of registrant as specified in its charter) Ireland 001-35676 98-1111119 (State or Other Jurisdiction of Incorpo

September 30, December 31, 2023 2022 Assets Cash and cash equivalents $ 670,897 $ 710,406 Restricted cash, current 1,352 — Prepaid expenses and other current assets 18,355 8,692 Total current assets 690,604 719,098 Property and equipment, net 2,433 1

Exhibit 99.1 PRESS RELEASE Prothena Reports Third Quarter 2023 Financial Results and Business Highlights •Net cash provided by operating and investing activities was $9.1 million in the third quarter and net cash used in operating and investing activities was $84.1 million for the first nine months of 2023; quarter-end cash and restricted cash position was $673.1 million •Received $55 million paym

Global License Agreement, dated as of July 5, 2023, by and between Prothena Biosciences Limited and Celgene Switzerland LLC

Exhibit 10.2 CERTAIN CONFIDENTIAL INFORMATION CONTAINED IN THIS DOCUMENT, MARKED BY [***], HAS BEEN OMITTED BECAUSE IT IS BOTH (I) NOT MATERIAL AND (II) IS THE TYPE THAT THE REGISTRANT TREATS AS PRIVATE OR CONFIDENTIAL. GLOBAL LICENSE AGREEMENT by and among PROTHENA BIOSCIENCES LIMITED and CELGENE SWITZERLAND LLC Dated as of July 5, 2023 TABLE OF CONTENTS LIST OF SCHEDULES SCHEDULE 1.27 EXISTING I

Financial Statements and Exhibits, Results of Operations and Financial Condition

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): November 2, 2023 PROTHENA CORPORATION PUBLIC LIMITED COMPANY (Exact name of registrant as specified in its charter) Ireland 001-35676 98-1111119 (State or Other Jurisdiction of Incorp

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-Q

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-Q (Mark One) ☒ QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the quarterly period ended September 30, 2023 Or ☐ TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 Commission file number: 001-35676 PROTHENA CORPORATION PUBLIC LIMITED COM

, between Prothena Biosciences Inc and Dennis J. Selkoe

Exhibit 10.1 CONSULTING AGREEMENT This Consulting Agreement (this “Agreement”) is effective as of October 1, 2023 (the “Effective Date”) and is made by and between Dennis J. Selkoe, M.D., an individual (“Consultant”), and Prothena Biosciences Inc, a Delaware corporation with offices at 331 Oyster Point Boulevard, South San Francisco, CA 94080, U.S.A. (“Prothena”). Consultant and Prothena may each

Prothena Corporation plc 77 Sir John Rogerson’s Quay, Block C Grand Canal Docklands Dublin 2, D02 VK60, Ireland

Prothena Corporation plc 77 Sir John Rogerson’s Quay, Block C Grand Canal Docklands Dublin 2, D02 VK60, Ireland August 4, 2023 United States Securities and Exchange Commission Division of Corporation Finance Office of Life Sciences 100 F Street, N.

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): August 3, 2023 PROTHENA CORPORATI

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): August 3, 2023 PROTHENA CORPORATION PUBLIC LIMITED COMPANY (Exact name of registrant as specified in its charter) Ireland 001-35676 98-1111119 (State or Other Jurisdiction of Incorpor

June 30, December 31, 2023 2022 Assets Cash and cash equivalents $ 659,111 $ 710,406 Restricted cash, current 1,352 — Prepaid expenses and other current assets 16,640 8,692 Total current assets 677,103 719,098 Property and equipment, net 2,170 1,731

Exhibit 99.1 PRESS RELEASE Prothena Reports Second Quarter 2023 Financial Results and Business Highlights •Net cash used in operating and investing activities was $45.7 million in the second quarter and $93.2 million for the first six months of 2023; quarter-end cash and restricted cash position was $661.3 million •Revised year-end cash guidance to be approximately $600 million in cash, cash equiv

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-Q

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-Q (Mark One) ☒ QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the quarterly period ended June 30, 2023 Or ☐ TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 Commission file number: 001-35676 PROTHENA CORPORATION PUBLIC LIMITED COMPANY

Calculation of Filing Fee Table.

Exhibit 107 Calculation of Filing Fee Tables Form S-8 (Form Type) Prothena Corporation Public Limited Company (Exact Name of Registrant as Specified in its Charter) Table 1: Newly Registered Securities Security Type Security Class Title Fee Calculation Rule Amount Registered(1) Proposed Maximum Offering Price Per Unit Maximum Aggregate Offering Price Fee Rate Amount of Registration Fee Equity(2) Ordinary Shares, par value $0.

As filed with the Securities and Exchange Commission on August 3, 2023

S-8 As filed with the Securities and Exchange Commission on August 3, 2023 Registration No.

Entry into a Material Definitive Agreement, Financial Statements and Exhibits

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): July 5, 2023 PROTHENA CORPORATION PUBLIC LIMITED COMPANY (Exact name of registrant as specified in its charter) Ireland 001-35676 98-1111119 (State or Other Jurisdiction of Incorporat

Fourth Amendment to the Prothena Corporation plc 2018 Long Term Incentive Plan. (6)

EX-10.1 Exhibit 10.1 FOURTH AMENDMENT TO THE PROTHENA CORPORATION PLC 2018 LONG TERM INCENTIVE PLAN This Fourth Amendment (this “Third Amendment”) to the Prothena Corporation plc 2018 Long Term Incentive Plan, as amended (“2018 LTIP”), 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”),

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): May 16, 2023 PROTHENA CORPORATION

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): May 16, 2023 PROTHENA CORPORATION PUBLIC LIMITED COMPANY (Exact name of registrant as specified in its charter) Ireland 001-35676 98-1111119 (State or Other Jurisdiction of Incorporat

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): May 16, 2023 PROTHENA CORPORATION

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): May 16, 2023 PROTHENA CORPORATION PUBLIC LIMITED COMPANY (Exact name of registrant as specified in its charter) Ireland 001-35676 98-1111119 (State or Other Jurisdiction of Incorporat

Fourteenth Amendment to the Prothena Corporation plc 2020 Employment Inducement Incentive Plan

Exhibit 10.1 FOURTEENTH AMENDMENT TO THE PROTHENA CORPORATION PLC 2020 EMPLOYMENT INDUCEMENT INCENTIVE PLAN This Fourteenth Amendment (this “Fourteenth 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

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-Q

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-Q (Mark One) ☒ QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the quarterly period ended March 31, 2023 Or ☐ TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 Commission file number: 001-35676 PROTHENA CORPORATION PUBLIC LIMITED COMPANY

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): May 4, 2023 PROTHENA CORPORATION

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): May 4, 2023 PROTHENA CORPORATION PUBLIC LIMITED COMPANY (Exact name of registrant as specified in its charter) Ireland 001-35676 98-1111119 (State or Other Jurisdiction of Incorporati

March 31, December 31, 2022 2023 2022 Assets Cash and cash equivalents $ 686,184 $ 710,406 Prepaid expenses and other current assets 14,159 8,692 Total current assets 700,343 719,098 Property and equipment, net 1,924 1,731 Operating lease right-of-us

Exhibit 99.1 PRESS RELEASE Prothena Reports First Quarter 2023 Financial Results and Business Highlights •Net cash used in operating and investing activities was $47.5 million in the first quarter of 2023; quarter-end cash and restricted cash position was $688.4 million •Data reported in an oral presentation at AD/PD 2023 that PRX012, a potential best-in-class anti-amyloid beta antibody, demonstra

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): April 25, 2023 PROTHENA CORPORATI

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): April 25, 2023 PROTHENA CORPORATION PUBLIC LIMITED COMPANY (Exact name of registrant as specified in its charter) Ireland 001-35676 98-1111119 (State or Other Jurisdiction of Incorpor

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 14A Proxy Statement Pursuant to Section 14(a) of the Securities Exchange Act of 1934

TABLE OF CONTENTS UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 14A Proxy Statement Pursuant to Section 14(a) of the Securities Exchange Act of 1934 Filed by the Registrant ☒ Filed by a Party other than the Registrant ☐ Check the appropriate box: ☐ Preliminary Proxy Statement ☐ Confidential, for Use of the Commission Only (as permitted by Rule 14a-6(e)(2)) ☒ Defi

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 14A Proxy Statement Pursuant to Section 14(a) of the Securities Exchange Act of 1934

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 14A Proxy Statement Pursuant to Section 14(a) of the Securities Exchange Act of 1934 Filed by the Registrant ☒ Filed by a Party other than the Registrant ☐ Check the appropriate box: ☐ Preliminary Proxy Statement ☐ Confidential, for Use of the Commission Only (as permitted by Rule 14a-6(e)(2)) ☐ Definitive Proxy State

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): March 10, 2023 PROTHENA CORPORATI

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): March 10, 2023 PROTHENA CORPORATION PUBLIC LIMITED COMPANY (Exact name of registrant as specified in its charter) Ireland 001-35676 98-1111119 (State or Other Jurisdiction of Incorpor

Consent to Sublease Agreement, dated as of October 28, 2022, by and among HCP LS Brisbane, LLC, Arcus Biosciences, Inc., and Prothena Biosciences Inc.

Exhibit 10.15(b) CONSENT TO SUBLEASE AGREEMENT THIS CONSENT TO SUBLEASE AGREEMENT (this "Agreement") is made as of October 28, 2022, by and among HCP LS BRISBANE, LLC, a Delaware limited liability company ("Landlord"), ARCUS BIOSCIENCES, INC., a Delaware corporation ("Tenant"), and PROTHENA BIOSCIENCES INC, a Delaware corporation ("Subtenant"). R E C I T A L S A.Reference is hereby made to that ce

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

Exhibit 10.22 FIRST AMENDMENT 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”

List of Subsidiaries

Exhibit 21.1 List of Subsidiaries Subsidiary Name Jurisdiction of Incorporation or Organization Prothena Biosciences Limited Ireland Prothena Biosciences Inc Delaware Prothena Finance Inc Delaware Othair Prothena Limited Ireland Prothena Pharma Limited Ireland Prothena Platform Technologies Limited Ireland

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-K

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-K (Mark One) ☒ ANNUAL REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the year ended December 31, 2022 ☐ TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the transition period from to Commission file number: 001-35676 PROTHENA CORPORATION PUB

Sublease, dated as of October 28, 2022, by and between Arcus Biosciences, Inc. and Prothena Biosciences Inc.

Exhibit 10.15(a) SUBLEASE THIS SUBLEASE (this “Sublease”) is dated for reference purposes as of October 28, 2022 (the “Effective Date”), and is made by and between Arcus Biosciences, Inc., a Delaware corporation (“Sublessor”), and Prothena Biosciences Inc, a Delaware corporation (“Sublessee”). Sublessor and Sublessee hereby agree as follows: 1.Recitals: This Sublease is made with reference to the

Description of Registrant’s Securities

EXHIBIT 4.2 DESCRIPTION OF REGISTRANT’S SECURITIES This description is summarized from, and qualified in its entirety by reference to, our Amended and Restated Memorandum and Articles of Association (our “Constitution”), each of which are incorporated by reference as exhibits to the Annual Report on Form 10-K of which this exhibit is a part. In this exhibit, unless the context otherwise requires,

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): February 23, 2023 PROTHENA CORPOR

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): February 23, 2023 PROTHENA CORPORATION PUBLIC LIMITED COMPANY (Exact name of registrant as specified in its charter) Ireland 001-35676 98-1111119 (State or Other Jurisdiction of Incor

December 31, December 31, 2021 2022 2021 Assets Cash and cash equivalents $ 710,406 $ 579,094 Prepaid expenses and other current assets 8,692 5,715 Total current assets 719,098 584,809 Property and equipment, net 1,731 2,012 Operating lease right-of-

Exhibit 99.1 PRESS RELEASE Prothena Reports Fourth Quarter and Full Year 2022 Financial Results, and Provides Financial Guidance and Business Highlights •Net cash used in operating and investing activities was $5.1 million in the fourth quarter and $109.3 million for the full year of 2022; quarter-end cash and restricted cash position was $712.6 million •Advanced potential best-in-class Alzheimer’

PRTA / Prothena Corp plc / SCULLY WILLIAM P - SC 13G/A Passive Investment

SC 13G/A 1 d423670dsc13ga.htm SC 13G/A UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 13G/A Under the Securities Exchange Act of 1934 (Amendment No. 1) * Prothena Corporation PLC (Name of Issuer) Ordinary Shares, $0.01 par value (Title of Class of Securities) G72800108 (CUSIP Number) Diana L. Hayes, Esq. Trenam Law 2700 Bank of America Plaza Tampa, Florida 33602 8

PRTA / Prothena Corp plc / Avidity Partners Management LP Passive Investment

SC 13G/A 1 d990838113g-a.htm UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, DC 20549 SCHEDULE 13G Under the Securities Exchange Act of 1934 (Amendment No.)* Prothena Corporation Public Limited Company (Name of Issuer) Ordinary Shares, par value $0.01 per share (Title of Class of Securities) G72800108 (CUSIP Number) December 31, 2022 (Date of Event Which Requires Filing of this Statem

Calculation of Filing Fee Tables (Form Type) Prothena Corporation plc (Exact Name of Registrant as Specified in its Charter) Table 1: Newly Registered and Carry Forward Securities Security Type Security Class Title Fee Calculation or Carry Forward Ru

Exhibit 107 Calculation of Filing Fee Tables 424(b)(5) (Form Type) Prothena Corporation plc (Exact Name of Registrant as Specified in its Charter) Table 1: Newly Registered and Carry Forward Securities Security Type Security Class Title Fee Calculation or Carry Forward Rule Amount Registered Proposed Maximum Offering Price Per Share Maximum Aggregate Offering Price Fee Rate Amount of Registration Fee(1) Carry Forward Form Type Carry Forward File Number Carry Forward Initial effective date Filing Fee Previously Paid In Connection with Unsold Securities to be Carried Forward Fees to Be Paid Equity Ordinary Shares, $0.

Underwriting Agreement dated December 14, 2022 by and among Prothena Corporation plc and the Representatives

EX-1.1 2 d378186dex11.htm EX-1.1 Exhibit 1.1 PROTHENA CORPORATION PLC (an Irish public limited company) 3,250,000 Ordinary Shares UNDERWRITING AGREEMENT Dated: December 14, 2022 PROTHENA CORPORATION PLC (an Irish public limited company) 3,250,000 Ordinary Shares ($0.01 nominal value per share) UNDERWRITING AGREEMENT December 14, 2022 Jefferies LLC Evercore Group L.L.C. Cantor Fitzgerald & Co. as R

3,250,000 Shares Ordinary Shares

Table of Contents Filed Pursuant to Rule 424(b)(5) Registration No. 333-254622 3,250,000 Shares Ordinary Shares Prothena Corporation plc is offering 3,250,000 of its ordinary shares. Our ordinary shares are listed on the Nasdaq Global Select Market under the symbol ?PRTA.? The closing price of our ordinary shares on the Nasdaq Global Select Market on December 14, 2022 was $57.97 per ordinary share

Financial Statements and Exhibits, Other Events

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): December 14, 2022 PROTHENA CORPORATION PUBLIC LIMITED COMPANY (Exact name of registrant as specified in its charter) Ireland 001-35676 98-1111119 (State or other jurisdiction of incor

SUBJECT TO COMPLETION, DATED DECEMBER 13, 2022 PRELIMINARY PROSPECTUS SUPPLEMENT TO PROSPECTUS DATED MARCH 23, 2021 3,000,000 Shares Ordinary Shares

424B5 Table of Contents Filed Pursuant to Rule 424(b)(5) Registration No. 333-254622 The information in this preliminary prospectus supplement and the accompanying prospectus is not complete and may be changed. This preliminary prospectus supplement and the accompanying prospectus are not an offer to sell nor do they seek an offer to buy these securities in any jurisdiction where the offer or sale

Financial Statements and Exhibits, Other Events

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): November 21, 2022 PROTHENA CORPORATION PUBLIC LIMITED COMPANY (Exact name of registrant as specified in its charter) Ireland 001-35676 98-1111119 (State or Other Jurisdiction of Incor

Prothena Announces Achievement of $40 Million Clinical Milestone Payment from Novo Nordisk for PRX004/NNC6019 Under Investigation for the Treatment of ATTR Cardiomyopathy

EXHIBIT 99.1 PRESS RELEASE Prothena Announces Achievement of $40 Million Clinical Milestone Payment from Novo Nordisk for PRX004/NNC6019 Under Investigation for the Treatment of ATTR Cardiomyopathy ?Prothena is eligible to receive development and sales milestone payments from Novo Nordisk totaling up to $1.2 billion, including $100 million announced to date ?PRX004/NNC6019 continues to advance in

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-Q

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-Q (Mark One) ? QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the quarterly period ended September 30, 2022 Or ? TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 Commission file number: 001-35676 PROTHENA CORPORATION PUBLIC LIMITED COM

, between Prothena Biosciences Inc and Dennis J. Selkoe

Exhibit 10.4 CONSULTING AGREEMENT This Consulting Agreement (this ?Agreement?) is effective as of October 1, 2022 (the ?Effective Date?) and is made by and between Dennis J. Selkoe, M.D., an individual (?Consultant?), and Prothena Biosciences Inc, a Delaware corporation with offices at 331 Oyster Point Boulevard, South San Francisco, CA 94080, U.S.A. (?Prothena?). Consultant and Prothena may each

September 30, December 31, 2021 2022 2021 Assets Cash and cash equivalents $ 495,628 $ 579,094 Prepaid expenses and other current assets 28,934 5,715 Total current assets 524,562 584,809 Property and equipment, net 1,997 2,012 Operating lease right-o

Exhibit 99.1 Prothena Reports Third Quarter 2022 Financial Results and Business Highlights ?Net cash used in operating and investing activities was $31.3 million in the third quarter and $104.2 million for the first nine months of 2022; quarter-end cash and restricted cash position was $497.0 million ?Phase 3 VITAL study data on observed survival benefit in Mayo Stage IV AL amyloidosis patients tr

Financial Statements and Exhibits, Results of Operations and Financial Condition

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): November 3, 2022 PROTHENA CORPORATION PUBLIC LIMITED COMPANY (Exact name of registrant as specified in its charter) Ireland 001-35676 98-1111119 (State or Other Jurisdiction of Incorp

Entry into a Material Definitive Agreement, Financial Statements and Exhibits

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): October 28, 2022 PROTHENA CORPORATION PUBLIC LIMITED COMPANY (Exact name of registrant as specified in its charter) Ireland 001-35676 98-1111119 (State or Other Jurisdiction of Incorp

Departure of Directors or Certain Officers; Election of Directors; Appointment of Certain Officers; Compensatory Arrangements of Certain Officers

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): August 30, 2022 PROTHENA CORPORATION PUBLIC LIMITED COMPANY (Exact name of registrant as specified in its charter) Ireland 001-35676 98-1111119 (State or Other Jurisdiction of Incorpo

Twelfth Amendment to the Prothena Corporation plc 2020 Employment Inducement Incentive Plan

Exhibit 4.9 TWELFTH AMENDMENT TO THE PROTHENA CORPORATION PLC 2020 EMPLOYMENT INDUCEMENT INCENTIVE PLAN This Twelfth Amendment (this ?Twelfth 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 ?Comp

As filed with the Securities and Exchange Commission on August 10, 2022

As filed with the Securities and Exchange Commission on August 10, 2022 Registration No.

Eleventh Amendment to the Prothena Corporation plc 2020 Employment Inducement Incentive Plan

Exhibit 4.8 ELEVENTH AMENDMENT TO THE PROTHENA CORPORATION PLC 2020 EMPLOYMENT INDUCEMENT INCENTIVE PLAN This Eleventh Amendment (this ?Eleventh 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 ?C

Thirteenth Amendment to the Prothena Corporation plc 2020 Employment Inducement Incentive Plan

Exhibit 4.10 THIRTEENTH AMENDMENT TO THE PROTHENA CORPORATION PLC 2020 EMPLOYMENT INDUCEMENT INCENTIVE PLAN This Thirteenth Amendment (this ?Thirteenth 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

Calculation of Filing Fee Table

Exhibit 107 Calculation of Filing Fee Table Form S-8 (Form Type) Prothena Corporation Public Limited Company (Exact Name of Registrant as Specified in its Charter) Table 1: Newly Registered Securities Security type Security Class Title Fee Calculation Rule Amount Registered (1) Proposed Maximum Offering Price Per Unit Maximum Aggregate Offering Price Fee Rate Amount of Registration Fee Equity (2) Ordinary Shares, par value $0.

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-Q

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-Q (Mark One) ? QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the quarterly period ended June 30, 2022 Or ? TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 Commission file number: 001-35676 PROTHENA CORPORATION PUBLIC LIMITED COMPANY

Financial Statements and Exhibits, Results of Operations and Financial Condition

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): August 8, 2022 PROTHENA CORPORATION PUBLIC LIMITED COMPANY (Exact name of registrant as specified in its charter) Ireland 001-35676 98-1111119 (State or Other Jurisdiction of Incorpor

June 30, December 31, 2021 2022 2021 Assets Cash and cash equivalents $ 508,795 $ 579,094 Prepaid expenses and other current assets 12,499 5,715 Total current assets 521,294 584,809 Property and equipment, net 1,861 2,012 Operating lease right-of-use

Exhibit 99.1 Prothena Reports Second Quarter 2022 Financial Results and Business Highlights ?Net cash used in operating and investing activities was $35.5 million in the second quarter and $72.9 million for the first six months of 2022; quarter-end cash and restricted cash position was $510.1 million ?Broad Alzheimer?s disease portfolio continues to advance: FDA Fast Track designation granted in A

PRTA / Prothena Corp plc / SCULLY WILLIAM P - SC 13G Passive Investment

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 13G Under the Securities Exchange Act of 1934 (Amendment No. ) * Prothena Corporation PLC (Name of Issuer) Ordinary Shares, $0.01 par value (Title of Class of Securities) G72800108 (CUSIP Number) Diana L. Hayes, Esq. Trenam Law 2700 Bank of America Plaza Tampa, Florida 33602 813-227-7433 (Name, Address and Telephone N

Departure of Directors or Certain Officers; Election of Directors; Appointment of Certain Officers; Compensatory Arrangements of Certain Officers, Financial Statements and Exhibits, Submission of Matters to a Vote of Security Holders

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): May 17, 2022 PROTHENA CORPORATION PUBLIC LIMITED COMPANY (Exact name of registrant as specified in its charter) Ireland 001-35676 98-1111119 (State or Other Jurisdiction of Incorporat

Third Amendment to the Prothena Corporation plc 2018 Long Term Incentive Plan

Exhibit 10.1 THIRD AMENDMENT TO THE PROTHENA CORPORATION PLC 2018 LONG TERM INCENTIVE PLAN This Third Amendment (this ?Third Amendment?) to the Prothena Corporation plc 2018 Long Term Incentive Plan, as amended (?2018 LTIP?), 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 Februar

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 14A Proxy Statement Pursuant to Section 14(a) of the Securities Exchange Act of 1934 Filed by the Registrant ☒ Filed by a Party other than the Registrant ☐

DEFA14A 1 d338243ddefa14a.htm DEFA14A UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 14A Proxy Statement Pursuant to Section 14(a) of the Securities Exchange Act of 1934 Filed by the Registrant ☒ Filed by a Party other than the Registrant ☐ Check the appropriate box: ☐ Preliminary Proxy Statement ☐ Confidential, for Use of the Commission Only (as permitted by Rule

Financial Statements and Exhibits, Results of Operations and Financial Condition

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): May 5, 2022 PROTHENA CORPORATION PUBLIC LIMITED COMPANY (Exact name of registrant as specified in its charter) Ireland 001-35676 98-1111119 (State or Other Jurisdiction of Incorporati

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-Q

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-Q (Mark One) ☒ QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the quarterly period ended March 31, 2022 Or ☐ TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 Commission file number: 001-35676 PROTHENA CORPORATION PUBLIC LIMITED COMPANY

March 31, December 31, 2021 2022 2021 Assets Cash and cash equivalents $ 542,994 $ 579,094 Prepaid expenses and other current assets 12,626 5,715 Total current assets 555,620 584,809 Property and equipment, net 1,865 2,012 Operating lease right-of-us

Exhibit 99.1 Prothena Reports First Quarter 2022 Financial Results and Business Highlights •Net cash used in operating and investing activities was $37.4 million in the first quarter; quarter-end cash and restricted cash position was $544.3 million •Advanced PRX012, a potential best-in-class, subcutaneous treatment for Alzheimer’s disease, into a Phase 1 clinical study and received FDA Fast Track

Financial Statements and Exhibits, Other Events

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): April 26, 2022 PROTHENA CORPORATION PUBLIC LIMITED COMPANY (Exact name of registrant as specified in its charter) Ireland 001-35676 98-1111119 (State or Other Jurisdiction of Incorpor

Prothena Receives FDA Fast Track Designation for PRX012, a Next-Generation Anti-Amyloid Beta Antibody Under Investigation for the Treatment of Alzheimer’s Disease

EX-99.1 2 exhibit991prx012fasttrackp.htm EX-99.1 EXHIBIT 99.1 Prothena Receives FDA Fast Track Designation for PRX012, a Next-Generation Anti-Amyloid Beta Antibody Under Investigation for the Treatment of Alzheimer’s Disease •PRX012 is a potential best-in-class, subcutaneous anti-amyloid beta antibody therapy currently in a Phase 1 clinical study for the treatment of Alzheimer’s disease DUBLIN, Ir

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 14A Proxy Statement Pursuant to Section 14(a) of the Securities Exchange Act of 1934 Filed by the Registrant ☒ Filed by a Party other than the Registrant ☐

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 14A Proxy Statement Pursuant to Section 14(a) of the Securities Exchange Act of 1934 Filed by the Registrant ? Filed by a Party other than the Registrant ? Check the appropriate box: ? Preliminary Proxy Statement ? Confidential, for Use of the Commission Only (as permitted by Rule 14a-6(e)(2)) ? Definitive Proxy State

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 14A (Rule 14a-101) INFORMATION REQUIRED IN PROXY STATEMENT SCHEDULE 14A INFORMATION Proxy Statement Pursuant to Section 14(a) of the Securities Exchange Act of 1934 (Ame

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 14A (Rule 14a-101) INFORMATION REQUIRED IN PROXY STATEMENT SCHEDULE 14A INFORMATION Proxy Statement Pursuant to Section 14(a) of the Securities Exchange Act of 1934 (Amendment No. ) Filed by the Registrant ? Filed by a Party other than the Registrant ? Check the appropriate box: ? Preliminary Proxy Statement ? Confide

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 14A Proxy Statement Pursuant to Section 14(a) of the Securities Exchange Act of 1934

DEF 14A 1 ny20001664x2def14a.htm DEF 14A TABLE OF CONTENTS UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 14A Proxy Statement Pursuant to Section 14(a) of the Securities Exchange Act of 1934 Filed by the Registrant ☒ Filed by a Party other than the Registrant ☐ Check the appropriate box: ☐ Preliminary Proxy Statement ☐ Confidential, for Use of the Commission Only

Prothena Announces FDA Clearance of IND for PRX012, a Subcutaneous Anti-Amyloid Beta Antibody Under Investigation for the Treatment of Alzheimer’s Disease

EXHIBIT 99.1 Prothena Announces FDA Clearance of IND for PRX012, a Subcutaneous Anti-Amyloid Beta Antibody Under Investigation for the Treatment of Alzheimer?s Disease ?Prothena has initiated Phase 1 SAD study of PRX012, under investigation for the treatment of Alzheimer?s disease DUBLIN, Ireland, March 28, 2022 - Prothena Corporation plc (NASDAQ:PRTA), a late-stage clinical company with a robust

Financial Statements and Exhibits, Other Events

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): March 28, 2022 PROTHENA CORPORATION PUBLIC LIMITED COMPANY (Exact name of registrant as specified in its charter) Ireland 001-35676 98-1111119 (State or Other Jurisdiction of Incorpor

Regulation FD Disclosure

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): March 25, 2022 PROTHENA CORPORATION PUBLIC LIMITED COMPANY (Exact name of registrant as specified in its charter) Ireland 001-35676 98-1111119 (State or Other Jurisdiction of Incorpor

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 14A Proxy Statement Pursuant to Section 14(a) of the Securities Exchange Act of 1934

TABLE OF CONTENTS UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 14A Proxy Statement Pursuant to Section 14(a) of the Securities Exchange Act of 1934 Filed by the Registrant ? ? ? ? ? Filed by a Party other than the Registrant ? ? ?? Check the appropriate box: ? Preliminary Proxy Statement ?? Confidential, for Use of the Commission Only (as permitted by Rule 14a-6

PRTA / Prothena Corp plc / First Light Asset Management, LLC - SCHEDULE FILED TO REPORT ACQUISITION OF BENEFICIAL OWNERSHIP Passive Investment

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 13G Under the Securities Exchange Act of 1934* Prothena Corporation, PLC (Name of Issuer) Common Stock, $0.01 par value (Title of Class of Securities) G72800108 (CUSIP Number) February 28, 2022 (Date of Event Which Requires Filing of this Statement) Check the appropriate box to designate the rule pursuant to which thi

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

Exhibit 10.20 FIRST AMENDMENT 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?

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-K

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-K (Mark One) ? ANNUAL REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the year ended December 31, 2021 ? TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the transition period from to Commission file number: 001-35676 PROTHENA CORPORATION PUB

Description of Registrant’s Securities

EXHIBIT 4.2 DESCRIPTION OF REGISTRANT?S SECURITIES This description is summarized from, and qualified in its entirety by reference to, our Amended and Restated Memorandum and Articles of Association (our ?Constitution?), each of which are incorporated by reference as exhibits to the Annual Report on Form 10-K of which this exhibit is a part. In this exhibit, unless the context otherwise requires,

List of Subsidiaries

Exhibit 21.1 List of Subsidiaries Subsidiary Name Jurisdiction of Incorporation or Organization Prothena Biosciences Limited Ireland Prothena Biosciences Inc Delaware Prothena Finance Inc Delaware Othair Prothena Limited Ireland Prothena Pharma Limited Ireland

December 31, 2021 2020 Assets Cash and cash equivalents $ 579,094 $ 295,380 Accounts receivable — 15 Prepaid expenses and other current assets 5,715 2,537 Restricted cash, current — 1,352 Total current assets 584,809 299,284 Property and equipment, n

Exhibit 99.1 Prothena Reports Fourth Quarter and Full Year 2021 Financial Results, and Provides Financial Guidance and Business Highlights ?Net cash used in operating and investing activities was $22.8 million in the fourth quarter and net cash provided by operating and investing activities was $92.0 million for the full year 2021; quarter-end cash and restricted cash position was $580.4 million ?

Financial Statements and Exhibits, Results of Operations and Financial Condition

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): February 17, 2022 PROTHENA CORPORATION PUBLIC LIMITED COMPANY (Exact name of registrant as specified in its charter) Ireland 001-35676 98-1111119 (State or Other Jurisdiction of Incor

PRTA / Prothena Corp plc / EcoR1 Capital, LLC Activist Investment

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 13D Under the Securities Exchange Act of 1934 (Amendment No. 3) Prothena Corporation Public Limited Company (Name of Issuer) Ordinary Shares, par value $0.01 per share (Title of Class of Securities) G72800108 (CUSIP Number) James J. Frolik, Esq. Anthony J. Caldwell, Esq. Shartsis Friese LLP One Maritime Plaza, 18th Fl

CALCULATION OF REGISTRATION FEE Title of Securities Being Registered Proposed Maximum Aggregate Offering Price(1) Amount of Registration Fee(2) Ordinary Shares, par value $0.01 per share $250,000,000 $23,175

Table of Contents Filed Pursuant to Rule 424(b)(5) Registration No. 333-254622 CALCULATION OF REGISTRATION FEE Title of Securities Being Registered Proposed Maximum Aggregate Offering Price(1) Amount of Registration Fee(2) Ordinary Shares, par value $0.01 per share $250,000,000 $23,175 (1) The proposed maximum aggregate offering price is being used to calculate the registration fee pursuant to Rul

Distribution Agreement, dated December 23 2021, by and among the Company, Piper Sandler & Co., Stifel, Nicolaus & Company, Incorporated, Cantor Fitzgerald & Co., RBC Capital Markets, LLC, and JMP Securities LLC.

Exhibit 1.1 PROTHENA CORPORATION PLC EQUITY DISTRIBUTION AGREEMENT December 23, 2021 PIPER SANDLER & CO. U.S. Bancorp Center 800 Nicollet Mall Minneapolis, Minnesota 55402 STIFEL, NICOLAUS & COMPANY, INCORPORATED One South Street, 15th Floor Baltimore, Maryland 21202 CANTOR FITZGERALD & CO. 499 Park Avenue, 6th Floor New York, New York 10022 RBC CAPITAL MARKETS, LLC 200 Vesey Street New York, New

Financial Statements and Exhibits, Other Events

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): December 23, 2021 PROTHENA CORPORATION PUBLIC LIMITED COMPANY (Exact name of registrant as specified in its charter) Ireland 001-35676 98-1111119 (State or Other Jurisdiction of Incor

U.S. License Agreement, dated as of July 30, 2021, as amended on August 12, 2021 and September 8, 2021, by and between Prothena Biosciences Limited and Celgene Switzerland LLC

[***] Certain information in this document has been excluded pursuant to Regulation S-K, Item 601(b)(10).

Amendment No. 2 to License, Development, and Commercialization Agreement, entered into on August 26, 2021, among Prothena Biosciences Limited, Prothena Biosciences Inc, F. Hoffman-La Roche Ltd and Hoffman-La Roche Inc.

Exhibit 10.3 [***] Certain information in this document has been excluded pursuant to Regulation S-K, Item 601(b)(10). Such excluded information is both not material and the type of information that the registrant customarily and actually treats as private and confidential. AMENDMENT NO. 2 TO LICENSE, DEVELOPMENT, AND COMMERCIALIZATION AGREEMENT This AMENDMENT NO. 2 (this ?Amendment No. 2?) is mad

Tenth Amendment to the Prothena Corporation plc 2020 Employment Inducement Incentive Plan

Exhibit 10.1 TENTH AMENDMENT TO THE PROTHENA CORPORATION PLC 2020 EMPLOYMENT INDUCEMENT INCENTIVE PLAN This Tenth Amendment (this ?Tenth 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?)

Amended and Restated Consulting Agreement, dated July 15, 2020, between Prothena Biosciences Inc and Dennis J. Selkoe

Exhibit 10.2 AMENDED AND RESTATED CONSULTING AGREEMENT This Amended and Restated Consulting Agreement (this ?Agreement?) is effective as of July 15, 2020 (the ?Effective Date?) and is made by and between Dennis J. Selkoe, M.D., an individual (?Consultant?), and Prothena Biosciences Inc, a Delaware corporation with offices at 331 Oyster Point Boulevard, South San Francisco, CA 94080, U.S.A. (?Proth

Financial Statements and Exhibits, Results of Operations and Financial Condition

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): November 4, 2021 PROTHENA CORPORATION PUBLIC LIMITED COMPANY (Exact name of registrant as specified in its charter) Ireland 001-35676 98-1111119 (State or Other Jurisdiction of Incorp

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-Q

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-Q (Mark One) ? QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the quarterly period ended September 30,2021 Or ? TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 Commission file number: 001-35676 PROTHENA CORPORATION PUBLIC LIMITED COMP

Share Purchase Agreement, dated as of July 8, 2021, by and among Novo Nordisk A/S, Novo Nordisk Region Europe A/S, Prothena Corporation plc, and Prothena Biosciences Limited

Exhibit 10.4 [***] Certain information in this document has been excluded pursuant to Regulation S-K, Item 601(b)(10). Such excluded information is both not material and the type of information that the registrant customarily and actually treats as private and confidential. SHARE PURCHASE AGREEMENT by and between NOVO NORDISK A/S; NOVO NORDISK REGION EUROPE A/S; PROTHENA CORPORATION PLC; and PROTH

September 30, December 31, 2021 2020 Assets Cash and cash equivalents $ 600,098 $ 295,380 Accounts receivable 79 15 Prepaid expenses and other current assets 7,353 2,537 Restricted cash, current — 1,352 Total current assets 607,530 299,284 Property a

Exhibit 99.1 Prothena Reports Third Quarter 2021 Financial Results and Business Highlights ?Net cash provided by operating and investing activities was $111.9 million in the third quarter and $114.8 million for the first nine months of 2021; Quarter-end cash and restricted cash position was $601.5 million ?Received $140 million from partner payments in third quarter from Novo Nordisk and Bristol M

Departure of Directors or Certain Officers; Election of Directors; Appointment of Certain Officers; Compensatory Arrangements of Certain Officers, Financial Statements and Exhibits

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): September 29, 2021 PROTHENA CORPORATION PUBLIC LIMITED COMPANY (Exact name of registrant as specified in its charter) Ireland 001-35676 98-1111119 (State or Other Jurisdiction of Inco

As filed with the Securities and Exchange Commission on August 6, 2021

As filed with the Securities and Exchange Commission on August 6, 2021 Registration No.

Financial Statements and Exhibits, Results of Operations and Financial Condition

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): August 5, 2021 PROTHENA CORPORATION PUBLIC LIMITED COMPANY (Exact name of registrant as specified in its charter) Ireland 001-35676 98-1111119 (State or Other Jurisdiction of Incorpor

Eighth Amendment to the Prothena Corporation plc 2020 Employment Inducement Incentive Plan

Exhibit 10.2 EIGHTH AMENDMENT TO THE PROTHENA CORPORATION PLC 2020 EMPLOYMENT INDUCEMENT INCENTIVE PLAN This Eighth Amendment (this ?Eighth 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 ?Compan

June 30, December 31, 2021 2020 Assets Cash and cash equivalents $ 399,831 $ 295,380 Accounts receivable 3 15 Prepaid expenses and other current assets 8,282 2,537 Restricted cash, current 1,352 1,352 Total current assets 409,468 299,284 Property and

Exhibit 99.1 Prothena Reports Second Quarter 2021 Financial Results and Business Highlights ?Net cash provided by operating and investing activities was $36.6 million in the second quarter and $2.9 million for the first six months of 2021; quarter-end cash and restricted cash position of $402.5 million (includes $60 million payment from Roche) provides additional funding to continue advancing R&D

Ninth Amendment to the Prothena Corporation plc 2020 Employment Inducement Incentive Plan

Exhibit 10.3 NINTH AMENDMENT TO THE PROTHENA CORPORATION PLC 2020 EMPLOYMENT INDUCEMENT INCENTIVE PLAN This Ninth Amendment (this ?Ninth 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?)

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-Q

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-Q (Mark One) ? QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the quarterly period ended June 30, 2021 Or ? TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 Commission file number: 001-35676 PROTHENA CORPORATION PUBLIC LIMITED COMPANY

Entry into a Material Definitive Agreement, Financial Statements and Exhibits

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): July 30, 2021 PROTHENA CORPORATION PUBLIC LIMITED COMPANY (Exact name of registrant as specified in its charter) Ireland 001-35676 98-1111119 (State or Other Jurisdiction of Incorpora

Prothena and Novo Nordisk Announce Acquisition Agreement for Prothena’s ATTR Amyloidosis Programme

EXHIBIT 99.1 Prothena and Novo Nordisk Announce Acquisition Agreement for Prothena?s ATTR Amyloidosis Programme ?Prothena is eligible to receive development and sales milestone payments totalling up to 1.2 billion US dollars, including 100 million dollars in upfront and near-term clinical milestone payments ?Novo Nordisk will develop the phase 2-ready antibody PRX004 for the rare heart disease ATT

Regulation FD Disclosure, Entry into a Material Definitive Agreement, Financial Statements and Exhibits

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): July 8, 2021 PROTHENA CORPORATION PUBLIC LIMITED COMPANY (Exact name of registrant as specified in its charter) Ireland 001-35676 98-1111119 (State or Other Jurisdiction of Incorporat

Financial Statements and Exhibits, Other Events

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): June 24, 2021 PROTHENA CORPORATION PUBLIC LIMITED COMPANY (Exact name of registrant as specified in its charter) Ireland 001-35676 98-1111119 (State or Other Jurisdiction of Incorpora

Prothena Announces Bristol Myers Squibb Opt-in of Anti-Tau PRX005 as the First Program from Global Neuroscience Research and Development Collaboration

EXHIBIT 99.1 Prothena Announces Bristol Myers Squibb Opt-in of Anti-Tau PRX005 as the First Program from Global Neuroscience Research and Development Collaboration ?Prothena to receive $80 million from Bristol Myers Squibb for exclusive US license to PRX005; Next option for worldwide rights following completion Phase 1 ?PRX005 is an investigational best-in-class anti-tau antibody targeting the mic

Financial Statements and Exhibits, Other Events

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): May 28, 2021 PROTHENA CORPORATION PUBLIC LIMITED COMPANY (Exact name of registrant as specified in its charter) Ireland 001-35676 98-1111119 (State or Other Jurisdiction of Incorporat

CALCULATION OF REGISTRATION FEE Title of Securities Being Registered Proposed Maximum Aggregate Offering Price(1) Amount of Registration Fee(2) Ordinary Shares, par value $0.01 per share $100,000,000 $10,910.00

Table of Contents Filed Pursuant to Rule 424(b)(5) Registration No. 333-254622 CALCULATION OF REGISTRATION FEE Title of Securities Being Registered Proposed Maximum Aggregate Offering Price(1) Amount of Registration Fee(2) Ordinary Shares, par value $0.01 per share $100,000,000 $10,910.00 (1) The proposed maximum aggregate offering price is being used to calculate the registration fee pursuant to

Distribution Agreement, dated May 28, 2021, by and among the Company, Piper Sandler & Co., Stifel, Nicolaus & Company, Incorporated, Cantor Fitzgerald & Co., RBC Capital Markets, LLC, and Raymond James & Associates, Inc.

Exhibit 1.1 PROTHENA CORPORATION PLC EQUITY DISTRIBUTION AGREEMENT May 28, 2021 PIPER SANDLER & CO. U.S. Bancorp Center 800 Nicollet Mall Minneapolis, Minnesota 55402 STIFEL, NICOLAUS & COMPANY, INCORPORATED One South Street, 15th Floor Baltimore, Maryland 21202 CANTOR FITZGERALD & CO. 499 Park Avenue, 6th Floor New York, New York 10022 RBC CAPITAL MARKETS, LLC 200 Vesey Street New York, New York

Other Events

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): May 28, 2021 PROTHENA CORPORATION PUBLIC LIMITED COMPANY (Exact name of registrant as specified in its charter) Ireland 001-35676 98-1111119 (State or Other Jurisdiction of Incorporat

Second Amendment to the Prothena Corporation plc 2018 Long Term Incentive Plan

Exhibit 10.1 SECOND AMENDMENT TO THE PROTHENA CORPORATION PLC 2018 LONG TERM INCENTIVE PLAN This Second Amendment (this ?Second Amendment?) to the Prothena Corporation plc 2018 Long Term Incentive Plan, as amended (?2018 LTIP?), 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 Febr

Departure of Directors or Certain Officers; Election of Directors; Appointment of Certain Officers; Compensatory Arrangements of Certain Officers, Financial Statements and Exhibits, Submission of Matters to a Vote of Security Holders

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): May 18, 2021 PROTHENA CORPORATION PUBLIC LIMITED COMPANY (Exact name of registrant as specified in its charter) Ireland 001-35676 98-1111119 (State or Other Jurisdiction of Incorporat

Departure of Directors or Certain Officers; Election of Directors; Appointment of Certain Officers; Compensatory Arrangements of Certain Officers

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): May 18, 2021 PROTHENA CORPORATION PUBLIC LIMITED COMPANY (Exact name of registrant as specified in its charter) Ireland 001-35676 98-1111119 (State or Other Jurisdiction of Incorporat

Offer Letter, dated March 18, 2021, between Prothena Biosciences Inc and Hideki Garren

Exhibit 10.1 Hideki Garren [Address Redacted] REVISED ? March 18, 2021 Dear Hideki: I am pleased to confirm this offer for you to join Prothena Biosciences Inc (?Prothena? or the ?Company?). We are confident in your knowledge, expertise and judgment, and believe your performance will meet our team?s high-quality objectives and standards. Your start date will be April 5, 2021, and the Prothena Corp

Financial Statements and Exhibits, Results of Operations and Financial Condition

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): May 11, 2021 PROTHENA CORPORATION PUBLIC LIMITED COMPANY (Exact name of registrant as specified in its charter) Ireland 001-35676 98-1111119 (State or Other Jurisdiction of Incorporat

March 31, December 31, 2021 2020 Assets Cash and cash equivalents $ 342,993 $ 295,380 Accounts receivable 1 15 Prepaid expenses and other current assets 7,955 2,537 Restricted cash, current 1,352 1,352 Total current assets 352,301 299,284 Property an

Exhibit 99.1 Prothena Reports First Quarter 2021 Financial Results, and Provides Updated Financial Guidance and R&D Update ?Net cash used in operating and investing activities was $33.7 million in the first quarter; quarter-end cash and restricted cash position of $345.7 million provides funding to advance the R&D pipeline ?Announced confirmatory Phase 3 AFFIRM-AL study of birtamimab in Mayo Stage

Quarterly Report - 10-Q

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-Q (Mark One) ? QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the quarterly period ended March 31, 2021 Or ? TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 Commission file number: 001-35676 PROTHENA CORPORATION PUBLIC LIMITED COMPANY

Seventh Amendment to the Prothena Corporation plc 2020 Employment Inducement Incentive Plan

Exhibit 10.2 SEVENTH AMENDMENT TO THE PROTHENA CORPORATION PLC 2020 EMPLOYMENT INDUCEMENT INCENTIVE PLAN This Seventh Amendment (this ?Seventh 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 ?Com

- DEFA14A

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 14A (Rule 14a-101) INFORMATION REQUIRED IN PROXY STATEMENT SCHEDULE 14A INFORMATION Proxy Statement Pursuant to Section 14(a) of the Securities Exchange Act of 1934 (Amendment No. ) Filed by the Registrant ? Filed by a Party other than the Registrant ? Check the appropriate box: ? Preliminary Proxy Statement ? Confide

Definitive Proxy Statement

TABLE OF CONTENTS UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 14A (Rule 14a-101) INFORMATION REQUIRED IN PROXY STATEMENT SCHEDULE 14A INFORMATION Proxy Statement Pursuant to Section 14(a) of the Securities Exchange Act of 1934 (Amendment No. ??) Filed by the Registrant ? ? ? ? ? Filed by a Party other than the Registrant ? ? ? Check the appropriate box: ? Preli

Financial Statements and Exhibits, Other Events

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): March 23, 2021 PROTHENA CORPORATION PUBLIC LIMITED COMPANY (Exact name of registrant as specified in its charter) Ireland 001-35676 98-1111119 (State or Other Jurisdiction of Incorpor

Underwriting Agreement, dated March 23, 2021, by and among Prothena Corporation plc and Citigroup Global Markets Inc., Jefferies LLC, and Cantor Fitzgerald & Co.

Exhibit 1.1 PROTHENA CORPORATION PLC (an Irish public limited company) 3,500,000 Ordinary Shares UNDERWRITING AGREEMENT Dated: March 23, 2021 PROTHENA CORPORATION PLC (an Irish public limited company) 3,500,000 Ordinary Shares ($0.01 nominal value per share) UNDERWRITING AGREEMENT March 23, 2021 Citigroup Global Markets Inc. Jefferies LLC Cantor Fitzgerald & Co. as Representatives of the several U

Title of Securities Being Registered

Table of Contents Filed Pursuant to Rule 424(b)(5) Registration No. 333-254622 Title of Securities Being Registered Amount to be Registered Proposed Maximum Offering Price Per Share Proposed Maximum Aggregate Offering Price Amount of Registration Fee(1) Ordinary Shares, par value $0.01 per share 4,025,000 shares(2) $20.75 $83,518,750 $9,111.90 (1) Calculated in accordance with Rule 457(r) under th

- S-3ASR

Table of Contents As filed with the Securities and Exchange Commission on March 23, 2021 Registration No.

SUBJECT TO COMPLETION, DATED MARCH 23, 2021 PRELIMINARY PROSPECTUS SUPPLEMENT TO PROSPECTUS DATED MARCH 23, 2021 Ordinary Shares

Table of Contents Filed Pursuant to Rule 424(b)(5) Registration No. 333-254622 The information in this preliminary prospectus supplement and the accompanying prospectus is not complete and may be changed. This preliminary prospectus supplement and the accompanying prospectus are not an offer to sell nor do they seek an offer to buy these securities in any jurisdiction where the offer or sale is no

- PRE 14A

TABLE OF CONTENTS UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 14A (Rule 14a-101) INFORMATION REQUIRED IN PROXY STATEMENT SCHEDULE 14A INFORMATION Proxy Statement Pursuant to Section 14(a) of the Securities Exchange Act of 1934 (Amendment No. ??) Filed by the Registrant ? ? ? ? ? Filed by a Party other than the Registrant ? ? ?? Check the appropriate box: ? Prel

List of Subsidiaries

Exhibit 21.1 List of Subsidiaries Subsidiary Name Jurisdiction of Incorporation or Organization Prothena Biosciences Limited Ireland Prothena Biosciences Inc Delaware Prothena Finance Inc Delaware Neotope Neuroscience Limited Ireland Othair Prothena Limited Ireland

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

EXHIBIT 10.17 FIRST AMENDMENT 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?

Annual Report - 10-K

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-K (Mark One) ? ANNUAL REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the year ended December 31, 2020 ? TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the transition period from to Commission file number: 001-35676 PROTHENA CORPORATION PUB

Description of Registrant’s Securities

EXHIBIT 4.2 DESCRIPTION OF REGISTRANT?S SECURITIES This description is summarized from, and qualified in its entirety by reference to, our Amended and Restated Memorandum and Articles of Association (our ?Constitution?), each of which are incorporated by reference as exhibits to the Annual Report on Form 10-K of which this exhibit is a part. In this exhibit, unless the context otherwise requires,

Consulting Agreement, dated July 15, 2020, between Prothena Biosciences Inc and Dennis J. Selkoe

EXHIBIT 10.35 CONSULTING AGREEMENT This Consulting Agreement (this ?Agreement?) is effective as of July 15, 2020 (the ?Effective Date?) and is made by and between Dennis J. Selkoe, M.D., an individual (?Consultant?), and Prothena Biosciences Inc, a Delaware corporation with offices at 331 Oyster Point Boulevard, South San Francisco, CA 94080, U.S.A. (?Prothena?). Consultant and Prothena may each b

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 13D Under the Securities Exchange Act of 1934 (Amendment No. 2) Prothena Corporation Public Limited Company (Name of Issuer) Ordinary Shares, par value $0.01 per share (

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 13D Under the Securities Exchange Act of 1934 (Amendment No. 2) Prothena Corporation Public Limited Company (Name of Issuer) Ordinary Shares, par value $0.01 per share (Title of Class of Securities) G72800108 (CUSIP Number) James J. Frolik, Esq. Anthony J. Caldwell, Esq. Shartsis Friese LLP One Maritime Plaza, 18th Fl

- AMENDMENT NO. 5 TO SC TO-I

SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 SCHEDULE TO/A (Amendment No. 5) Tender Offer Statement Under Section 14(d)(1) or 13(e)(1) of the Securities Exchange Act of 1934 PROTHENA CORPORATION PUBLIC LIMITED COMPANY (Name of Subject Company (Issuer)) PROTHENA CORPORATION PUBLIC LIMITED COMPANY (Name of Filing Person (Offeror)) Options To Purchase Ordinary Shares, Par Value $0.01 Per

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 13G Under the Securities Exchange Act of 1934*

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 13G Under the Securities Exchange Act of 1934* Prothena Corporation, PLC (Name of Issuer) Common Stock, $0.01 par value (Title of Class of Securities) G72800108 (CUSIP Number) December 31, 2020 (Date of Event Which Requires Filing of this Statement) Check the appropriate box to designate the rule pursuant to which thi

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, DC 20549 SCHEDULE 13G/A Under the Securities Exchange Act of 1934 (Amendment No. 2)* Prothena Corporation Public Limited Company

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, DC 20549 SCHEDULE 13G/A Under the Securities Exchange Act of 1934 (Amendment No.

JOINT FILING AGREEMENT

CUSIP No. G72800108 SCHEDULE 13G Page 8 of 8 Pages EXHIBIT A JOINT FILING AGREEMENT The undersigned hereby agree that the Statement on this Schedule 13G dated February 12, 2021 (the “Schedule 13G”), with respect to the Ordinary Shares, par value of $0.01 per share, of Prothena Corporation Public Limited Company is filed on behalf of each of us pursuant to and in accordance with the provisions of R

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, DC 20549 SCHEDULE 13G Under the Securities Exchange Act of 1934 (Amendment No. 1)*

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, DC 20549 SCHEDULE 13G Under the Securities Exchange Act of 1934 (Amendment No.

December 31, 2020 2019 Assets Cash and cash equivalents $ 295,380 $ 375,723 Accounts receivable 15 68 Prepaid expenses and other current assets 2,537 2,584 Restricted cash, current 1,352 — Total current assets 299,284 378,375 Property and equipment,

Exhibit 99.1 Prothena Reports Fourth Quarter and Full Year 2020 Financial Results, and Provides Financial Guidance and R&D Update •Net cash used in operating and investing activities was $19.1 million in the fourth quarter and $80.6 million for the full year 2020; quarter-end cash and restricted cash position of $298.1 million provides funding to advance the R&D pipeline •Announced confirmatory Ph

Financial Statements and Exhibits, Results of Operations and Financial Condition

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): February 11, 2021 PROTHENA CORPORATION PUBLIC LIMITED COMPANY (Exact name of registrant as specified in its charter) Ireland 001-35676 98-1111119 (State or Other Jurisdiction of Incor

Offer to Exchange Certain Outstanding Options to Purchase Ordinary Shares, dated November 9, 2020

EX-(a)(1)(i) Exhibit (a)(1)(i) PROTHENA CORPORATION PLC OFFER TO EXCHANGE CERTAIN OUTSTANDING OPTIONS TO PURCHASE ORDINARY SHARES FOR A NUMBER OF REPLACEMENT OPTIONS THIS OFFER AND WITHDRAWAL RIGHTS EXPIRE AT 9:00 P.

- AMENDMENT NO. 4 TO SC TO-I

Amendment No. 4 to SC TO-I SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 SCHEDULE TO/A (Amendment No. 4) Tender Offer Statement Under Section 14(d)(1) or 13(e)(1) of the Securities Exchange Act of 1934 PROTHENA CORPORATION PUBLIC LIMITED COMPANY (Name of Subject Company (Issuer)) PROTHENA CORPORATION PUBLIC LIMITED COMPANY (Name of Filing Person (Offeror)) Options To Purchase Ordinary

Prothena Announces Confirmatory Phase 3 AFFIRM-AL Study of Birtamimab in Mayo Stage IV Patients with AL Amyloidosis under SPA Agreement with FDA

Prothena Announces Confirmatory Phase 3 AFFIRM-AL Study of Birtamimab in Mayo Stage IV Patients with AL Amyloidosis under SPA Agreement with FDA •Significant survival benefit observed in VITAL study for birtamimab-treated patients with AL amyloidosis at high risk for early mortality (Mayo Stage IV, HR=0.

Financial Statements and Exhibits, Other Events - 8-K

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): February 1, 2021 PROTHENA CORPORATION PUBLIC LIMITED COMPANY (Exact name of registrant as specified in its charter) Ireland 001-35676 98-1111119 (State or Other Jurisdiction of Incorp

Form of Reminder Email Communication

EX-99.(a)(1)(v) Exhibit (a)(1)(v) FORM OF REMINDER EMAIL COMMUNICATION TO: [ ] FROM: [email protected] DATE: [ ] Our records show you have not made an election to participate in the Option Exchange Program. This email is to remind you that February 12, 2021, at 9 P.M. Pacific Time is the final deadline to participate in the Option Exchange Program. If you wish to surrender your eligible

Option Exchange Frequently Asked Questions

EX-99.(a)(1)(ix) Exhibit (a)(1)(ix) OPTION EXCHANGE FREQUENTLY ASKED QUESTIONS The following are answers to some of the questions that you may have about the option exchange. We urge you to read carefully the following questions and answers, as well as the remainder of the Offer to Exchange, which is also available on the option exchange website. We suggest that you consult with your personal fina

Offer to Exchange Certain Outstanding Options to Purchase Ordinary Shares, dated November 9, 2020

EX-99.(a)(1)(i) Exhibit (a)(1)(i) PROTHENA CORPORATION PLC OFFER TO EXCHANGE CERTAIN OUTSTANDING OPTIONS TO PURCHASE ORDINARY SHARES FOR A NUMBER OF REPLACEMENT OPTIONS THIS OFFER AND WITHDRAWAL RIGHTS EXPIRE AT 9:00 P.M. PACIFIC TIME ON FEBRUARY 12, 2021 UNLESS THIS OFFER IS EXTENDED Prothena Corporation plc which is sometimes referred to herein as the “Company,” “Prothena,” “our,” “us,” or “we,”

Second Email to All Eligible Participants Regarding Updated Termination Date

EX-99.(a)(1)(xii) Exhibit (a)(1)(xii) EMAIL TO ALL ELIGIBLE PARTICIPANTS REGARDING UPDATED TERMINATION DATE To: Eligible Prothena Participants From: [email protected] Date: January 28, 2021 Re: Extension of Deadline to Participate in Prothena’s Option Exchange Program We are contacting you today to notify you that the deadline for participation in Prothena’s option exchange program has b

Form of Announcement Email

EX-99.(a)(1)(iv) Exhibit (a)(1)(iv) FORM OF ANNOUNCEMENT EMAIL TO ELIGIBLE PARTICIPANTS TO: [Participant] FROM: [email protected] SUBJECT: IMPORTANT NEWS: Launch of Option Exchange Program DATE: November 9, 2020 IMPORTANT NEWS - PLEASE READ IMMEDIATELY. SHOULD YOU CHOOSE TO PARTICIPATE IN THIS PROGRAM, YOU MUST TAKE ACTION BY 9:00 P.M., PACIFIC TIME, ON DECEMBER 8, 2020. We are pleased

Form of Terms of Election

EX-99.(a)(1)(iii) Exhibit (a)(1)(iii) PROTHENA CORPORATION PLC TERMS OF ELECTION BY PARTICIPATING, YOU AGREE TO ALL TERMS OF THE OFFER AS SET FORTH IN THE OFFER TO EXCHANGE CERTAIN OUTSTANDING OPTIONS TO PURCHASE ORDINARY SHARES FOR A NUMBER OF REPLACEMENT OPTIONS, DATED NOVEMBER 9, 2020 (AS IT MAY BE AMENDED FROM TIME TO TIME, THE “OFFER TO EXCHANGE”). If you would like to participate in this Off

Form of Email Confirming Receipt of Election

EX-99.(a)(1)(vi) Exhibit (a)(1)(vi) FORM OF EMAIL CONFIRMING RECEIPT OF ELECTION TO: [ ] FROM: [email protected] SUBJECT: Option Exchange Election Confirmation DATE: [ ] OPTION EXCHANGE PROGRAM [Name], Your Option Exchange election has been recorded as follows: Grant Date Eligible Options Per Share Exercise Price Election Exchange Ratio Replacement Options We strongly encourage you to p

- AMENDMENT NO. 3 TO SC TO-I

AMENDMENT NO. 3 TO SC TO-I SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 SCHEDULE TO/A (Amendment No. 3) Tender Offer Statement Under Section 14(d)(1) or 13(e)(1) of the Securities Exchange Act of 1934 PROTHENA CORPORATION PUBLIC LIMITED COMPANY (Name of Subject Company (Issuer)) PROTHENA CORPORATION PUBLIC LIMITED COMPANY (Name of Filing Person (Offeror)) Options To Purchase Ordinary

Form of Final Reminder Email

EX-99.(a)(1)(vii) Exhibit (a)(1)(vii) FORM OF FINAL REMINDER EMAIL COMMUNICATION TO: [ ] FROM: [email protected] DATE: February 11, 2021 This email is to remind you that tomorrow, February 12, 2021, at 9 P.M. Pacific Time is the final deadline to participate in the Option Exchange Program. If you wish to surrender your eligible options in exchange for new replacement options, as describ

Offer to Exchange Certain Outstanding Options to Purchase Ordinary Shares, dated November 9, 2020

EX-99.(a)(1)(i) Exhibit (a)(1)(i) PROTHENA CORPORATION PLC OFFER TO EXCHANGE CERTAIN OUTSTANDING OPTIONS TO PURCHASE ORDINARY SHARES FOR A NUMBER OF REPLACEMENT OPTIONS THIS OFFER AND WITHDRAWAL RIGHTS EXPIRE AT 9:00 P.M. PACIFIC TIME ON JANUARY 29, 2021 UNLESS THIS OFFER IS EXTENDED Prothena Corporation plc which is sometimes referred to herein as the “Company,” “Prothena,” “our,” “us,” or “we,”

- AMENDMENT NO. 2 TO SC TO-I

Amendment No. 2 to SC TO-I SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 SCHEDULE TO/A (Amendment No. 2) Tender Offer Statement Under Section 14(d)(1) or 13(e)(1) of the Securities Exchange Act of 1934 PROTHENA CORPORATION PUBLIC LIMITED COMPANY (Name of Subject Company (Issuer)) PROTHENA CORPORATION PUBLIC LIMITED COMPANY (Name of Filing Person (Offeror)) Options To Purchase Ordinary

Financial Statements and Exhibits, Other Events - 8-K

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): December 9, 2020 PROTHENA CORPORATION PUBLIC LIMITED COMPANY (Exact name of registrant as specified in its charter) Ireland 001-35676 98-1111119 (State or Other Jurisdiction of Incorp

Prothena Reports Positive 9 Month Results from Phase 1 Long-term Extension Study of PRX004, the First Investigational Anti-Amyloid Immunotherapy for the Treatment of ATTR Amyloidosis

Exhibit 99.1 Prothena Reports Positive 9 Month Results from Phase 1 Long-term Extension Study of PRX004, the First Investigational Anti-Amyloid Immunotherapy for the Treatment of ATTR Amyloidosis •Slowing of neuropathy progression for all 7 evaluable patients, evidenced by a +1.29 point mean change in NIS, was more favorable than expected progression of +9.2 points •Improvement in neuropathy for 3

Option Exchange Frequently Asked Questions

EX-(a)(1)(ix) Exhibit (a)(1)(ix) OPTION EXCHANGE FREQUENTLY ASKED QUESTIONS The following are answers to some of the questions that you may have about the option exchange.

Form of Final Reminder Email

EX-99.(A)(1)(VII) 6 d201720dex99a1vii.htm EX-(A)(1)(VII) Exhibit (a)(1)(vii) FORM OF FINAL REMINDER EMAIL COMMUNICATION TO: [ ] FROM: [email protected] DATE: January 28, 2021 Our records show you have not made an election to participate in the Option Exchange Program. This email is to remind you that tomorrow, January 29, 2021, at 9 P.M. Pacific Time is the final deadline to participate

- AMENDMENT NO. 1 TO SC TO-I

Amendment No. 1 to SC TO-I SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 SCHEDULE TO/A (Amendment No. 1) Tender Offer Statement Under Section 14(d)(1) or 13(e)(1) of the Securities Exchange Act of 1934 PROTHENA CORPORATION PUBLIC LIMITED COMPANY (Name of Subject Company (Issuer)) PROTHENA CORPORATION PUBLIC LIMITED COMPANY (Name of Filing Person (Offeror)) Options To Purchase Ordinary

Form of Reminder Email Communication

EX-(a)(1)(v) Exhibit (a)(1)(v) FORM OF REMINDER EMAIL COMMUNICATION TO: [ ] FROM: info@mail.

Email to All Eligible Participants Regarding Updated Termination Date

EX-(a)(1)(xi) Exhibit (a)(1)(xi) EMAIL TO ALL ELIGIBLE PARTICIPANTS REGARDING UPDATED TERMINATION DATE To: Eligible Prothena Participants From: OptionExchange@prothena.

Form of Email Confirming Receipt of Election

EX-(a)(1)(vi) Exhibit (a)(1)(vi) FORM OF EMAIL CONFIRMING RECEIPT OF ELECTION TO: [ ] FROM: info@mail.

Form of Terms of Election

EX-(a)(1)(iii) Exhibit (a)(1)(iii) PROTHENA CORPORATION PLC TERMS OF ELECTION BY PARTICIPATING, YOU AGREE TO ALL TERMS OF THE OFFER AS SET FORTH IN THE OFFER TO EXCHANGE CERTAIN OUTSTANDING OPTIONS TO PURCHASE ORDINARY SHARES FOR A NUMBER OF REPLACEMENT OPTIONS, DATED NOVEMBER 9, 2020 (AS IT MAY BE AMENDED FROM TIME TO TIME, THE “OFFER TO EXCHANGE”).

Offer to Exchange Certain Outstanding Options to Purchase Ordinary Shares, dated November 9, 2020

EX-(a)(1)(i) Exhibit (a)(1)(i) PROTHENA CORPORATION PLC OFFER TO EXCHANGE CERTAIN OUTSTANDING OPTIONS TO PURCHASE ORDINARY SHARES FOR A NUMBER OF REPLACEMENT OPTIONS THIS OFFER AND WITHDRAWAL RIGHTS EXPIRE AT 9:00 P.

Email to all eligible participants from Gene Kinney, Ph.D.

EX-99.(a)(1)(ii) Exhibit (a)(1)(ii) EMAIL TO ALL ELIGIBLE PARTICIPANTS FROM GENE KINNEY, PH.D., PROTHENA’S CHIEF EXECUTIVE OFFICER, DATED NOVEMBER 9, 2020 To: Eligible Prothena Participants From: [email protected], on behalf of Gene Kinney, Ph.D., President and Chief Executive Officer Date: November 9, 2020 Re: Prothena’s Option Exchange Program We are pleased to announce that Prothena i

Form of Reminder Email Communication

EX-99.(a)(1)(v) Exhibit (a)(1)(v) FORM OF REMINDER EMAIL COMMUNICATION TO: [ ] FROM: [email protected] DATE: [ ], 2020 Our records show you have not made an election to participate in the Option Exchange Program. This email is to remind you that December 8, 2020, at 9 P.M. Pacific Time is the final deadline to participate in the Option Exchange Program. If you wish to surrender your eli

Option Exchange Frequently Asked Questions

EX-99.(a)(1)(ix) Exhibit (a)(1)(ix) OPTION EXCHANGE FREQUENTLY ASKED QUESTIONS The following are answers to some of the questions that you may have about the option exchange. We urge you to read carefully the following questions and answers, as well as the remainder of the Offer to Exchange, which is also available on the option exchange website. We suggest that you consult with your personal fina

Form of Option Award Agreement between Prothena Corporation plc and employees under the Prothena Corporation plc 2012 Long Term Incentive Plan

EX-99.(d)(10) Exhibit (d)(10) PROTHENA CORPORATION PLC AMENDED AND RESTATED 2012 LONG TERM INCENTIVE PLAN Option Award Agreement – Cover Sheet Prothena Corporation plc, an Irish public limited company (“Company”), hereby grants an Option to acquire its Shares to the individual named below. The terms and conditions of the Option are set forth in this cover sheet, in the attached Option Award Agreem

Form of Option Award Agreement between Prothena Corporation plc and employees in Ireland under the Prothena Corporation plc 2012 Long Term Incentive Plan

EX-99.(d)(12) Exhibit (d)(12) PROTHENA CORPORATION PLC AMENDED AND RESTATED 2012 LONG TERM INCENTIVE PLAN Option Award Agreement – Cover Sheet Prothena Corporation plc, an Irish public limited company (“Company”), hereby grants an Option to acquire its Shares to the individual named below. The terms and conditions of the Option are set forth in this cover sheet, in the attached Option Award Agreem

- SC TO-I

SC TO-I SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 SCHEDULE TO Tender Offer Statement Under Section 14(d)(1) or 13(e)(1) of the Securities Exchange Act of 1934 PROTHENA CORPORATION PUBLIC LIMITED COMPANY (Name of Subject Company (Issuer)) PROTHENA CORPORATION PUBLIC LIMITED COMPANY (Name of Filing Person (Offeror)) Options To Purchase Ordinary Shares, Par Value $0.01 Per Share (Titl

Form of Option Award Agreement between Prothena Corporation plc and employees under the Prothena Corporation plc 2018 Long Term Incentive Plan

EX-99.(d)(9) Exhibit (d)(9) PROTHENA CORPORATION PLC 2018 LONG TERM INCENTIVE PLAN Option Award Agreement – Cover Sheet Prothena Corporation plc, an Irish public limited company (the “Company”), hereby grants an Option to acquire its Shares to the individual named below. The terms and conditions of the Option are set forth in this cover sheet, in the attached Option Award Agreement and in the Prot

Screen Shots of Option Exchange Website

EX-99.(a)(1)(viii) Exhibit (a)(1)(viii) WelcomeElection FormValue CalculatorResourcesLogout Option Exchange Program Commencement Date: November 9, 2020 Expiration Time: December 8, 2020 at 9:00 PM PST Welcome to the Option Exchange Program. We are offering you the Opportunity to exchange certain grants of your outstanding options for a lesser number of options with an exercise price equal to th cl

Form of Announcement Email

EX-99.(a)(1)(iv) Exhibit (a)(1)(iv) FORM OF ANNOUNCEMENT EMAIL TO ELIGIBLE PARTICIPANTS TO: [Participant] FROM: [email protected] SUBJECT: IMPORTANT NEWS: Launch of Option Exchange Program DATE: November 9, 2020 IMPORTANT NEWS - PLEASE READ IMMEDIATELY. SHOULD YOU CHOOSE TO PARTICIPATE IN THIS PROGRAM, YOU MUST TAKE ACTION BY 9:00 P.M., PACIFIC TIME, ON DECEMBER 8, 2020. We are pleased

Form of Terms of Election

EX-99.(a)(1)(iii) Exhibit (a)(1)(iii) PROTHENA CORPORATION PLC TERMS OF ELECTION BY PARTICIPATING, YOU AGREE TO ALL TERMS OF THE OFFER AS SET FORTH IN THE OFFER TO EXCHANGE CERTAIN OUTSTANDING OPTIONS TO PURCHASE ORDINARY SHARES FOR A NUMBER OF REPLACEMENT OPTIONS, DATED NOVEMBER 9, 2020 (AS IT MAY BE AMENDED FROM TIME TO TIME, THE “OFFER TO EXCHANGE”). If you would like to participate in this Off