As of November 6, 2026, Prothena Corp. Public Ltd. Co. is a publicly traded company (Nasdaq: PRTA); its largest reported holder is Fidelity (FMR), with 13.8% on Schedule 13G/A of August 6, 2026, then Fennell Todd W. (10.2%) (Schedule 13G/A, August 6, 2026).
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Is Prothena Corp. Public Ltd. Co. a real, registered company?
- Prothena Corp Public LTD Co files with the SEC under CIK 1559053 (its SEC filings).
- Its shares are listed under the ticker PRTA on Nasdaq (SEC company record).
- Incorporated in L2; business address in Dublin 2, L2, as its SEC filings state.
- Court and bankruptcy records: see Before you sign or pay below.
Before you sign or pay
- Court and bankruptcy: No federal court case or bankruptcy filing found under PROTHENA CORP PUBLIC LTD CO in our court records and SEC 8-K records (as of 2026-11-06).
- Leadership changes: the latest reported is Chad J. Swanson (Form 8-K filed 2026-10-02). Check you are dealing with the people now in charge.
- Ownership: 5%+ holders are reported on Schedule 13D or 13G; the latest names Fennell Todd W. (filed 2026-08-19).
Who are Prothena Corp. Public Ltd. Co.'s owners and officers?
Prothena Corp. Public Ltd. Co.: business address in Dublin 2, L2; industry Pharmaceutical Preparations (Form D, 2026-10-02).
| Report | Holder | Share |
|---|---|---|
| Schedule 13G/A, 2026-08-19 | Fennell Todd W. | 10.2% |
| Schedule 13G/A, 2026-08-14 | Fennell Todd W. | 9.8% |
| Schedule 13G/A, 2026-08-06 | Fmr LLC | 13.8% |
| Schedule 13G/A, 2026-07-29 | Blackrock, Inc. | 6.9% |
| Schedule 13G/A, 2026-05-15 | Rubric Capital Management LP | 9.29% |
| Schedule 13G/A, 2026-05-11 | Scully William P | 10.3% |
| Schedule 13G, 2026-02-13 | Rubric Capital Management LP | 6.83% |
| Schedule 13G/A, 2025-11-14 | Adar1 Capital Management, LLC | 2.7% |
| Schedule 13G/A, 2025-11-12 | Fennell Todd W. | 8.4% |
| Schedule 13G/A, 2025-11-12 | Scully William P | 9.8% |
| Schedule 13G/A, 2025-10-17 | Blackrock, Inc. | 5.7% |
| Schedule 13G/A, 2025-08-14 | Logos Global Management LP | 0% |
Questions about who owns Prothena Corp. Public Ltd. Co.
Who owns Prothena Corp. Public Ltd. Co.?
On this page, 5 holders' latest ownership filings report 5% or more of Prothena Corp. Public Ltd. Co.: Fmr LLC (13.8%, Schedule 13G/A, filed 2026-08-06), Scully William P (10.3%, Schedule 13G/A, filed 2026-05-11), Fennell Todd W. (10.2%, Schedule 13G/A, filed 2026-08-19), Rubric Capital Management LP (9.29%, Schedule 13G/A, filed 2026-05-15) and Blackrock, Inc. (6.9%, Schedule 13G/A, filed 2026-07-29).
Who are the largest shareholders of Prothena Corp. Public Ltd. Co.?
By the share each holder's latest filing reports, the largest holders of Prothena Corp. Public Ltd. Co. on this page are Fmr LLC (13.8%), Scully William P (10.3%) and Fennell Todd W. (10.2%).
When did Fmr LLC buy into Prothena Corp. Public Ltd. Co.?
The filings give report dates, not purchase dates. The earliest filing from Fmr LLC on this page is the Schedule 13G/A, filed 2026-08-06, reporting 13.8%. That earliest filing is itself an amendment, which updates an earlier report.
Is this an audit or a full list?
Neither. The ownership list on this page covers only Schedule 13D and 13G filings, which holders make once they own 5% or more of a class of shares (an amendment can report a stake that has since fallen below 5%); 12 such filings are shown here. It is not an audit and not a full cap table: holders who never reached 5% are not listed, and a stake can change after its latest filing.
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What the Full Report on Prothena Corp. Public Ltd. Co. covers
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What They Do, And How The Money Works
Who Runs It, And How To Reach Them
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Who Pays Them, And Who They Are Up Against
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| Filed | Person | Role | Change | Effective |
|---|---|---|---|---|
| Form 8-K, 2026-10-02 | Chad J. Swanson | departed |
Which insiders own Prothena Corp. Public Ltd. Co. shares?
Directors, officers and holders of 10% or more report their shares on Forms 3, 4 and 5. Each line is the latest such report, largest holding first.
- EcoR1 Capital, LLC, a 10% owner: 5,304,596 shares (10.3% of shares outstanding), held indirectly (the form names the holder only in its footnotes) (Form 4, 2025-05-06).
- , a 10% owner: 2,469,444 shares (4.8% of shares outstanding), 1,753,444 held directly and 716,000 indirectly (Form 4, 2026-10-29).
- , the chief legal officer: 80,000 shares (0.16% of shares outstanding) (Form 4, 2025-07-30).
- , the chief executive and president: 68,793 shares (0.13% of shares outstanding) (Form 4, 2026-07-30).
- , the chief strategy officer: 55,782 shares (0.11% of shares outstanding) (Form 4, 2026-07-30).
Shares outstanding: 51,349,796 as of 2026-10-29, from the company's latest SEC cover page.
How much has Prothena Corp. Public Ltd. Co. raised?
No fundraising or offering filing from Prothena Corp. Public Ltd. Co. is on file with us.
Keep reading
More on Prothena Corp. Public Ltd. Co. and the records around it.
Prothena Corp. Public Ltd. Co. elsewhere on the record
- 5%+ stake filings Aug 2026
Companies that share a holder
- Logos Global Management LP also filed stake reports on 14 other companies: Longeveron Inc. (Sep 2026), ACHIEVE LIFE SCIENCES, INC. (Aug 2026), Yarrow Bioscience, Inc. (Aug 2026)
- ADAR1 Capital Management, LLC also filed stake reports on 29 other companies: InMed Pharmaceuticals, Inc. (Oct 2026), Tenax Therapeutics, Inc. (Sep 2026), Adagio Medical Holdings, Inc. (Aug 2026)
- Rubric Capital Management LP also filed stake reports on 32 other companies: ARDELYX, INC. (Aug 2026), Enovis Corporation (Aug 2026), MeiraGTx Holdings plc (Aug 2026)
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