Prothena Ownership | Who Owns Prothena?

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Prothena Ownership Summary

Prothena is owned by 21.40% institutional investors, 19.33% insiders, and 59.27% retail investors. Fmr is the largest institutional shareholder, holding 14.68% of PRTA shares. Vanguard Health Care Inv is the top mutual fund, with 7.77% of its assets in Prothena shares.

PRTA Ownership Benchmark

Type	Name	% Inst	% Insiders	% Retail
Stock	Prothena	21.40%	19.33%	59.27%
Sector	Healthcare Stocks	42.54%	10.83%	46.63%
Industry	Biotech Stocks	45.22%	10.75%	44.04%

Institutional Shareholders

Top Institutional Shareholders by Total Shares

Holder	Shares	% Holding	Value
Fmr	7.90M	14.68%	$77.12M
Blackrock	3.86M	7.18%	$79.61M
Blackrock funding, inc. /de	3.60M	6.69%	$35.12M
Vanguard group	2.05M	3.81%	$20.01M
Armistice capital	1.82M	3.39%	$17.80M
Rubric capital management lp	1.54M	2.86%	$15.03M
Adar1 capital management	1.47M	2.73%	$14.34M
Palo alto investors lp	1.32M	2.46%	$12.92M
Acadian asset management	1.24M	2.30%	$12.09M
Geode capital management	1.02M	1.89%	$9.95M

Top Institutional Shareholders by % of Total Assets

Holder	Shares	% Assets	Value
Rangeley capital	560.46K	4.73%	$5.47M
Birchview capital, lp	549.02K	4.05%	$5.36M
Palo alto investors lp	1.32M	2.39%	$12.92M
Monimus capital management, lp	258.06K	1.55%	$2.52M
Adar1 capital management	1.47M	1.35%	$14.34M
Sandia investment management lp	29.95K	0.87%	$292.31K
Boxer capital	690.00K	0.75%	$14.24M
Dcf advisers	200.75K	0.63%	$1.96M
Artal group	1.00M	0.53%	$20.67M
Corton capital	14.21K	0.34%	$138.67K

Top Buyers

Holder	Shares	% Assets	Change
Rubric capital management lp	1.54M	0.17%	1.54M
Arrowstreet capital, limited partnership	654.29K	0.00%	654.29K
Point72 asset management	646.75K	0.01%	646.75K
Jpmorgan chase	735.76K	0.00%	608.81K
Balyasny asset management	575.79K	0.01%	575.79K

Top Sellers

Holder	Shares	% Assets	Change
Ecor1 capital	-	-	-11.58M
Adar1 capital management	1.47M	1.35%	-1.91M
Siren	-	-	-1.28M
Finepoint capital lp	-	-	-640.07K
Federated hermes	692.82K	0.01%	-488.27K

New Positions

Holder	Shares	% Assets	Change	Value
Rubric capital management lp	1.54M	0.17%	1.54M	$15.03M
Arrowstreet capital, limited partnership	654.29K	0.00%	654.29K	$6.39M
Point72 asset management	646.75K	0.01%	646.75K	$6.31M
Jump financial	186.25K	0.02%	186.25K	$1.82M
Janney montgomery scott	106.90K	0.00%	106.90K	$1.04M

Sold Out

Holder	Change
Koesten, hirschmann & crabtree	-1.00
Jfs wealth advisors	-2.00
Cbiz investment advisory services	-2.00
Cypress capital	-2.00
Hallmark capital management	-3.00

Institutional Ownership Trends

Date	Holdings	Change %	Shares	Change %	Ownership	Change %	Increased Position	Change %	Decreased Position	Change %
Sep 30, 2025	79	-60.70%	11,520,268	-72.42%	21	0.36%	36	-66.67%	20	-51.22%
Jun 30, 2025	198	17.86%	41,726,109	-20.15%	77	0.82%	107	81.36%	41	-33.87%
Mar 31, 2025	6	-96.69%	2,463,987	-95.40%	4	0.05%	2	-98.06%	4	-88.89%
Dec 31, 2024	107	-35.93%	25,474,325	-49.96%	47	0.53%	63	-12.50%	19	-57.78%
Sep 30, 2024	166	0.61%	50,906,096	0.22%	94	1.06%	71	-18.39%	45	9.76%

Top Mutual Funds Shareholders

Holder	Shares	% Holding	Change
Vanguard Health Care Inv	4.18M	7.77%	-39.90K
Fidelity Growth Compy Commingled Pl S	3.38M	6.29%	4.27K
Fidelity Growth Compy Commingled Pl O	3.28M	6.09%	1.22K
Fidelity Growth Company Fund	2.31M	4.29%	-13.83K
T. Rowe Price New Horizons	1.64M	3.04%	-251.35K
US Small-Cap Growth II Equity Comp	1.64M	3.04%	-251.90K
iShares Russell 2000 ETF	948.28K	1.76%	-
Fidelity Growth Company K6	803.14K	1.49%	9.55K
Federated Hermes MDT Small Cap Core IS	784.12K	1.46%	404.94K
Federated Hermes MDT SCC Institutional	784.12K	1.46%	404.94K

Recent Insider Transactions

Date	Name	Role	Activity	Value
May 06, 2025	EcoR1 Capital, LLC	-	Sell	$15.16M
May 05, 2025	EcoR1 Capital, LLC	-	Sell	$7.93M
May 02, 2025	EcoR1 Capital, LLC	-	Sell	$27.74M
Dec 31, 2024	SCULLY WILLIAM P	-	Buy	$389.64K
Dec 18, 2024	SCULLY WILLIAM P	-	Buy	$1.02M

Insider Transactions Trends

Date	Buy	Sell
2025 Q3	-	-
2025 Q2	-	3
2025 Q1	1	-
2024 Q4	-	-
2024 Q3	-	-

PRTA Ownership FAQ

Who Owns Prothena?

Prothena shareholders are primarily institutional investors at 21.40%, followed by 19.33% insiders and 59.27% retail investors. The average institutional ownership in Prothena's industry, Biotech Stocks , is 45.22%, which Prothena falls below.

Who owns the most shares of Prothena?

Prothena’s largest shareholders are Fmr (7.9M shares, 14.68%), Blackrock (3.86M shares, 7.18%), and Blackrock funding, inc. /de (3.6M shares, 6.69%). Together, they hold 28.54% of Prothena’s total shares outstanding.

Does Blackrock own Prothena?

Yes, BlackRock owns 7.18% of Prothena, totaling 3.86M shares as of Jun 2024. This represents 0.00% of BlackRock's total assets, with a market value of 79.61M$. In the last quarter, BlackRock increased its holdings by 138.27K shares, a 3.72% change.

Who is Prothena’s biggest shareholder by percentage of total assets invested?

Rangeley capital is Prothena’s biggest shareholder by percentage of total assets invested, with 4.73% of its assets in 560.46K Prothena shares, valued at 5.47M$.

Who is the top mutual fund holder of Prothena shares?

Vanguard Health Care Inv is the top mutual fund holder of Prothena shares, with 7.77% of its total shares outstanding invested in 4.18M Prothena shares.

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