Prothena Ownership | Who Owns Prothena?

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Prothena Ownership Summary

Prothena is owned by 88.66% institutional investors, 21.10% insiders. Fmr is the largest institutional shareholder, holding 13.40% 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	88.66%	21.10%	-9.76%
Sector	Healthcare Stocks	244.59%	12.11%	-156.70%
Industry	Biotech Stocks	379.61%	11.70%	-291.31%

Institutional Shareholders

Top Institutional Shareholders by Total Shares

Holder	Shares	% Holding	Value
Fmr	7.20M	13.40%	$70.48M
Rubric capital management lp	5.00M	9.31%	$48.95M
Blackrock funding, inc. /de	4.87M	9.06%	$47.66M
Blackrock	3.86M	7.18%	$79.61M
State street	2.39M	4.46%	$23.43M
Vanguard group	2.14M	3.98%	$20.45M
Acadian asset management	2.01M	3.74%	$19.68M
D. e. shaw	1.61M	3.00%	$15.78M
Adar1 capital management	1.55M	2.89%	$15.22M
Two sigma investments, lp	1.26M	2.36%	$12.38M

Top Institutional Shareholders by % of Total Assets

Holder	Shares	% Assets	Value
Rangeley capital	417.27K	3.73%	$4.09M
Birchview capital, lp	449.02K	2.06%	$4.40M
Penbrook management	271.72K	1.70%	$2.66M
Palo alto investors lp	1.14M	1.55%	$11.19M
Sandia investment management lp	29.95K	0.87%	$292.31K
Boxer capital	690.00K	0.75%	$14.24M
Monimus capital management, lp	329.05K	0.75%	$3.22M
Adar1 capital management	1.55M	0.70%	$15.22M
Artal group	1.00M	0.53%	$20.67M
Rubric capital management lp	5.00M	0.45%	$48.95M

Top Buyers

Holder	Shares	% Assets	Change
Balyasny asset management	575.79K	0.01%	575.79K
Acadian asset management	2.01M	0.02%	463.05K
State street	2.39M	0.00%	454.93K
Algert global	445.81K	0.07%	397.66K
Sixth street partners management company	355.90K	0.00%	355.90K

Top Sellers

Holder	Shares	% Assets	Change
Ecor1 capital	-	-	-11.58M
Siren	-	-	-1.28M
Finepoint capital lp	-	-	-640.07K
Rock springs capital management lp	25.40K	0.01%	-467.20K
Granahan investment management	-	-	-461.08K

New Positions

Holder	Shares	% Assets	Change	Value
Sixth street partners management company	355.90K	0.00%	355.90K	$3.48M
Mackenzie financial	239.90K	0.00%	239.90K	$2.35M
State of wisconsin investment board	70.33K	0.00%	70.33K	$688.49K
Norges bank	57.45K	0.00%	57.45K	$795.74K
Engineers gate manager lp	41.27K	0.01%	41.27K	$404.03K

Sold Out

Holder	Change
Wealth preservation advisors	-1.00
Truvestments capital	-1.00
Koesten, hirschmann & crabtree	-1.00
Jfs wealth advisors	-2.00
Cypress capital	-2.00

Institutional Ownership Trends

Date	Holdings	Change %	Shares	Change %	Ownership	Change %	Increased Position	Change %	Decreased Position	Change %
Jun 30, 2026	195	1.04%	47,615,367	1.35%	88	1.16%	89	-9.18%	57	14.00%
Mar 31, 2026	186	-3.63%	45,019,824	-4.73%	83	1.09%	96	18.52%	49	-20.97%
Dec 31, 2025	80	-60.00%	12,971,151	-69.58%	24	0.38%	30	-67.39%	25	-58.33%
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%

Top Mutual Funds Shareholders

Holder	Shares	% Holding	Change
Vanguard Health Care Inv	4.18M	7.77%	-39.90K
Fidelity Growth Compy Commingled Pl S	3.34M	6.37%	-94.30K
Fidelity Growth Compy Commingled Pl O	3.28M	6.09%	1.22K
Fidelity Growth Company Fund	2.23M	4.26%	-65.85K
US Small-Cap Growth II Equity Comp	1.64M	3.04%	-251.90K
T. Rowe Price New Horizons	1.64M	3.04%	-251.35K
State Street® SPDR® S&P® Biotech ETF	1.43M	2.73%	3.29K
iShares Russell 2000 ETF	1.14M	2.18%	-20.26K
Vanguard Explorer Inv	757.20K	1.45%	139.98K
Fidelity Series Growth Company	738.00K	1.41%	-20.90K

Recent Insider Transactions

Date	Name	Role	Activity	Value
Sep 02, 2026	SCULLY WILLIAM P	-	Buy	$255.74K
Aug 20, 2026	SCULLY WILLIAM P	-	Buy	$439.43K
Aug 07, 2026	SCULLY WILLIAM P	-	Buy	$30.17K
Aug 07, 2026	SCULLY WILLIAM P	-	Buy	$293.05K
Jul 29, 2026	Kingston Anne Evans	Chief Strategy Officer	Sell	$64.92K

Insider Transactions Trends

Date	Buy	Sell
2026 Q3	4	2
2026 Q2	5	-
2026 Q1	-	-
2025 Q3	-	-
2025 Q2	-	3

PRTA Ownership FAQ

Who Owns Prothena?

Prothena shareholders are primarily institutional investors at 88.66%, followed by 21.10% insiders and -9.76% retail investors. The average institutional ownership in Prothena's industry, Biotech Stocks , is 379.61%, which Prothena falls below.

Who owns the most shares of Prothena?

Prothena’s largest shareholders are Fmr (7.2M shares, 13.40%), Rubric capital management lp (5M shares, 9.31%), and Blackrock funding, inc. /de (4.87M shares, 9.06%). Together, they hold 31.78% 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 3.73% of its assets in 417.27K Prothena shares, valued at 4.09M$.

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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