Prothena Corporation plc
Ownership
Ownership Structure
Who owns Prothena Corporation plc (PRTA)? This page shows the largest institutions and funds, the ownership structure and the latest insider transactions. 66.5% of the shares are freely tradable; institutional investors hold 90.7%.
Largest Shareholders
Institutions
| Name | Stake (%) | Shares | Change (%) | Date |
|---|---|---|---|---|
| FMR Inc | 14.02 | 7,199,218 | -4.7 | 06/30/2026 |
| Rubric Capital Management LP | 9.74 | 5,000,000 | +0.0 | 06/30/2026 |
| BlackRock Inc | 9.48 | 4,867,955 | +4.8 | 06/30/2026 |
| State Street Corp | 4.66 | 2,393,424 | +23.5 | 06/30/2026 |
| Acadian Asset Management LLC | 3.92 | 2,010,645 | +29.9 | 06/30/2026 |
| Vanguard Portfolio Management, LLC | 3.22 | 1,651,293 | +14.2 | 06/30/2026 |
| D. E. Shaw & Co LP | 3.14 | 1,611,457 | -8.6 | 06/30/2026 |
| ADAR1 Capital Management LLC | 3.03 | 1,554,535 | -1.7 | 06/30/2026 |
| Two Sigma Investments LLC | 2.46 | 1,264,987 | +4.9 | 06/30/2026 |
Funds
| Name | Stake (%) | Shares | Change (%) | Date |
|---|---|---|---|---|
| Fidelity Growth Company Fund | 4.26 | 2,185,075 | -1.9 | 08/31/2026 |
Largest reported positions according to regulatory filings; stake as a percentage of shares outstanding, change versus the previous filing. Source: fundamentals data.
Insider holdings
| Person | Role | Shares | Value | As of | Type |
|---|---|---|---|---|---|
| Scully William P | 10% Owner | 2,469,444 | 20,249,441 $ | Sep 28, 2026 | both |
| Kinney Gene G. | President and CEO | 68,793 | 564,103 $ | Jul 28, 2026 | direct |
| Kingston Anne Evans | Chief Strategy Officer | 55,782 | 457,412 $ | Jul 29, 2026 | direct |
| Smith Brandon S. | Chief Operating Officer | 52,000 | 426,400 $ | Jul 28, 2026 | direct |
| Swanson Chad J. | Chief Development Officer | 40,733 | 334,011 $ | Jul 28, 2026 | direct |
| Nguyen Tran | Chief Strategy Officer and CFO | 40,205 | 329,681 $ | Jul 28, 2026 | direct |
| Isaacs Michael John | General Counsel & Company Sec. | 35,745 | 293,109 $ | Jul 29, 2026 | direct |
| Zago Wagner M. | Chief Scientific Officer | 34,000 | 278,800 $ | Jul 28, 2026 | direct |
| Walker Karin L | Chief Accounting Officer | 10,000 | 82,000 $ | Jul 28, 2026 | direct |
Holdings as of each person's most recent SEC Form 4 filing — excluding options and RSUs, which are not shares yet. Holdings may have changed between two filings.
Insiders
Insider Transactions
| Date | Person | Role | Type | Shares | Price | Value |
|---|---|---|---|---|---|---|
| Oct 27, 2026 | Scully William P | 10% Owner | Other | 566,444 | 0.00 | – |
| Oct 23, 2026 | Scully William P | 10% Owner | Buy | 50,000 | 8.07 | 403,525 |
| Oct 22, 2026 | Scully William P | 10% Owner | Buy | 100,000 | 8.19 | 818,520 |
| Oct 14, 2026 | Scully William P | 10% Owner | Buy | 10,000 | 8.46 | 84,569 |
| Oct 13, 2026 | Scully William P | 10% Owner | Buy | 100,000 | 8.35 | 835,480 |
| Oct 8, 2026 | Scully William P | 10% Owner | Buy | 90,000 | 8.57 | 770,904 |
| Oct 7, 2026 | Scully William P | 10% Owner | Buy | 125,000 | 8.40 | 1,050,150 |
| Oct 2, 2026 | Scully William P | 10% Owner | Buy | 100,000 | 8.57 | 857,240 |
| Sep 29, 2026 | Scully William P | 10% Owner | Buy | 162,000 | 8.68 | 1,405,674 |
| Sep 28, 2026 | Scully William P | 10% Owner | Buy | 103,500 | 8.60 | 889,872 |
| Sep 18, 2026 | Scully William P | 10% Owner | Buy | 100,000 | 8.43 | 843,460 |
| Sep 2, 2026 | Scully William P | 10% Owner | Buy | 27,000 | 9.47 | 255,739 |
| Aug 20, 2026 | Scully William P | 10% Owner | Buy | 50,000 | 8.79 | 439,430 |
| Aug 18, 2026 | Scully William P | 10% Owner | Other | 627,553 | 0.00 | – |
| Aug 17, 2026 | Scully William P | 10% Owner | Other | 336,000 | 0.00 | – |
| Aug 10, 2026 | Scully William P | 10% Owner | Other | 251,553 | 0.00 | – |
| Aug 7, 2026 | Scully William P | 10% Owner | Buy | 3,500 | 8.62 | 30,167 |
| Aug 7, 2026 | Scully William P | 10% Owner | Buy | 34,000 | 8.62 | 293,053 |
| Jul 29, 2026 | Kingston Anne Evans | Chief Strategy Officer | Sell | 7,662 | 8.47 | 64,919 |
| Jul 29, 2026 | Isaacs Michael John | General Counsel & Company Sec. | Sell | 8,386 | 8.47 | 71,055 |
| Jul 28, 2026 | Zago Wagner M. | Chief Scientific Officer | Other | 51,000 | 8.56 | 436,560 |
| Jul 28, 2026 | Zago Wagner M. | Chief Scientific Officer | Other | 51,000 | – | – |
| Jul 28, 2026 | Walker Karin L | Chief Accounting Officer | Other | 15,000 | 8.56 | 128,400 |
| Jul 28, 2026 | Walker Karin L | Chief Accounting Officer | Other | 15,000 | – | – |
| Jul 28, 2026 | Swanson Chad J. | Chief Development Officer | Other | 3,467 | 8.56 | 29,678 |
| Jul 28, 2026 | Swanson Chad J. | Chief Development Officer | Other | 40,800 | 8.56 | 349,248 |
| Jul 28, 2026 | Swanson Chad J. | Chief Development Officer | Other | 51,000 | – | – |
| Jul 28, 2026 | Smith Brandon S. | Chief Operating Officer | Other | 78,000 | 8.56 | 667,680 |
| Jul 28, 2026 | Smith Brandon S. | Chief Operating Officer | Other | 78,000 | – | – |
| Jul 28, 2026 | Nguyen Tran | Chief Strategy Officer and CFO | Other | 57,000 | 8.56 | 487,920 |
| Jul 28, 2026 | Nguyen Tran | Chief Strategy Officer and CFO | Other | 57,000 | – | – |
| Jul 28, 2026 | Kinney Gene G. | President and CEO | Other | 84,000 | 8.56 | 719,040 |
| Jul 28, 2026 | Kinney Gene G. | President and CEO | Other | 84,000 | – | – |
| Jul 28, 2026 | Kingston Anne Evans | Chief Strategy Officer | Other | 3,498 | 8.56 | 29,943 |
| Jul 28, 2026 | Isaacs Michael John | General Counsel & Company Sec. | Other | 4,694 | 8.56 | 40,181 |
Reportable transactions by officers and major shareholders from SEC Form 4 filings. "Other" includes things like stock grants and option exercises without a buy/sell character. View all insider transactions →
Data as of: November 3, 2026 · Source: fundamental data & SEC filings (annual and quarterly reports, 10-K/10-Q)
Note: pure fact-based analysis, not investment advice and not a solicitation to buy or sell. All figures without guarantee.