Prothena Ownership

Who are the major shareholders and have insiders been buying or selling?

Recent Insider Transactions

NasdaqGS:PRTA Recent Insider Transactions by Companies or Individuals
Date	Value	Name	Entity	Shares	Max Price
29 May 25	SellUS$28,753,036	EcoR1 Capital, LLC	Company	5,304,596	US$7.27
06 May 25	SellUS$50,839,807	EcoR1 Capital, LLC	Company	6,279,684	US$8.36
14 Jan 25	BuyUS$2,749,916	William Scully	Individual	207,436	US$15.91

Insider Trading Volume

Insider Buying: Insufficient data to determine if insiders have bought more shares than they have sold in the past 3 months.

Ownership Breakdown

What is the ownership structure of PRTA?
Owner Type	Number of Shares	Ownership Percentage
Individual Insiders	10,438,360	19.3%
Institutions	43,671,350	80.7%

Dilution of Shares: Shareholders have not been meaningfully diluted in the past year.

Top Shareholders

Top 25 shareholders own 78.46% of the company

Ownership	Name	Shares	Current Value	Change %	Portfolio %
14.7%	FMR LLC	7,901,218	US$75.4m	0%	no data
9.81%	William Scully	5,281,846	US$50.4m	-1.31%	no data
8.35%	Todd Fennell	4,495,846	US$42.9m	3.33%	no data
6.68%	BlackRock, Inc.	3,598,417	US$34.3m	-8.66%	no data
3.81%	The Vanguard Group, Inc.	2,049,849	US$19.6m	-5.81%	no data
3.39%	Armistice Capital LLC	1,824,000	US$17.4m	-18.4%	0.45%
2.86%	Rubric Capital Management LP	1,540,373	US$14.7m	0%	0.19%
2.73%	ADAR1 Capital Management, LLC	1,469,098	US$14.0m	-56.5%	1.24%
2.46%	Palo Alto Investors LP	1,324,028	US$12.6m	3.87%	1.84%
2.44%	D. E. Shaw & Co., L.P.	1,315,418	US$12.5m	236%	0.01%
2.3%	Acadian Asset Management LLC	1,239,242	US$11.8m	21.7%	0.02%
1.89%	Geode Capital Management, LLC	1,019,483	US$9.7m	9.22%	no data
1.67%	State Street Global Advisors, Inc.	901,038	US$8.6m	-10.3%	no data
1.63%	Jacobs Levy Equity Management Inc	876,528	US$8.4m	26.5%	0.03%
1.57%	Point72 Asset Management, L.P.	844,073	US$8.1m	60.4%	0.01%
1.5%	Dimensional Fund Advisors LP	806,988	US$7.7m	-16.1%	no data
1.43%	Citadel Advisors LLC	767,105	US$7.3m	-33.2%	0.01%
1.29%	Federated Hermes, Inc.	692,818	US$6.6m	-41.3%	0.01%
1.23%	Teachers Insurance and Annuity Association-College Retirement Equities Fund	664,393	US$6.3m	450%	no data
1.22%	Arrowstreet Capital, Limited Partnership	654,294	US$6.2m	0%	no data
1.15%	Millennium Management LLC	621,099	US$5.9m	264%	no data
1.15%	Jane Street Group, LLC	619,792	US$5.9m	428%	0.01%
1.1%	Mariner, LLC	590,897	US$5.6m	52.8%	0.01%
1.06%	Candriam, Société En Commandite Par Actions	571,819	US$5.5m	0%	0.01%
1.05%	Morgan Stanley	563,330	US$5.4m	-6.69%	no data

Company Analysis and Financial Data Status

Data	Last Updated (UTC time)
Company Analysis	2025/12/29 16:36
End of Day Share Price	2025/12/26 00:00
Earnings	2025/09/30
Annual Earnings	2024/12/31

Data Sources

The data used in our company analysis is from S&P Global Market Intelligence LLC. The following data is used in our analysis model to generate this report. Data is normalised which can introduce a delay from the source being available.

Package	Data	Timeframe	Example US Source ^*
Company Financials	10 years	Income statement Cash flow statement Balance sheet	SEC Form 10-K SEC Form 10-Q
Analyst Consensus Estimates	+3 years	Forecast financials Analyst price targets	Analyst Research Reports Blue Matrix
Market Prices	30 years	Stock prices Dividends, Splits and Actions	ICE Market Data SEC Form S-1
Ownership	10 years	Top shareholders Insider trading	SEC Form 4 SEC Form 13D
Management	10 years	Leadership team Board of directors	SEC Form 10-K SEC Form DEF 14A
Key Developments	10 years	Company announcements	SEC Form 8-K

^* Example for US securities, for non-US equivalent regulatory forms and sources are used.

Unless specified all financial data is based on a yearly period but updated quarterly. This is known as Trailing Twelve Month (TTM) or Last Twelve Month (LTM) Data. Learn more.

Analysis Model and Snowflake

Details of the analysis model used to generate this report is available on our Github page, we also have guides on how to use our reports and tutorials on Youtube.

Learn about the world class team who designed and built the Simply Wall St analysis model.

Industry and Sector Metrics

Our industry and section metrics are calculated every 6 hours by Simply Wall St, details of our process are available on Github.

Analyst Sources

Prothena Corporation plc is covered by 23 analysts. 6 of those analysts submitted the estimates of revenue or earnings used as inputs to our report. Analysts submissions are updated throughout the day.

Analyst	Institution
Geoffrey Meacham	Barclays
Tazeen Ahmad	BofA Global Research
null null	BTIG