Prothena Ownership | Who Owns Prothena?
Prothena Ownership Summary
Prothena is owned by 83.63% institutional investors, 19.87% insiders. Fmr is the largest institutional shareholder, holding 14.03% 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 | 83.63% | 19.87% | -3.50% |
| Sector | Healthcare Stocks | 35.58% | 11.87% | 52.55% |
| Industry | Biotech Stocks | 35.75% | 11.83% | 52.41% |
Institutional Shareholders
Top Institutional Shareholders by Total Shares
| Holder | Shares | % Holding | Value |
|---|---|---|---|
| Fmr | 7.55M | 14.03% | $73.40M |
| Rubric capital management lp | 5.00M | 9.29% | $48.60M |
| Blackrock funding, inc. /de | 4.64M | 8.63% | $45.14M |
| Blackrock | 3.86M | 7.18% | $79.61M |
| Vanguard group | 2.14M | 3.98% | $20.45M |
| State street | 1.94M | 3.60% | $18.84M |
| D. e. shaw | 1.76M | 3.28% | $17.14M |
| Acadian asset management | 1.55M | 2.88% | $15.04M |
| Adar1 capital management | 1.47M | 2.73% | $14.34M |
| Morgan stanley | 1.23M | 2.29% | $11.96M |
Top Institutional Shareholders by % of Total Assets
| Holder | Shares | % Assets | Value |
|---|---|---|---|
| Rangeley capital | 449.46K | 4.24% | $4.37M |
| Birchview capital, lp | 449.02K | 2.48% | $4.36M |
| Penbrook management | 271.72K | 2.00% | $2.64M |
| Palo alto investors lp | 1.21M | 1.80% | $11.75M |
| Adar1 capital management | 1.47M | 1.35% | $14.34M |
| Monimus capital management, lp | 485.62K | 1.31% | $4.72M |
| Sandia investment management lp | 29.95K | 0.87% | $292.31K |
| Boxer capital | 690.00K | 0.75% | $14.24M |
| Artal group | 1.00M | 0.53% | $20.67M |
| Rubric capital management lp | 5.00M | 0.51% | $48.60M |
Top Buyers
| Holder | Shares | % Assets | Change |
|---|---|---|---|
| Rubric capital management lp | 5.00M | 0.51% | 1.32M |
| Balyasny asset management | 575.79K | 0.01% | 575.79K |
| Blackrock funding, inc. /de | 4.64M | 0.00% | 536.70K |
| Two sigma investments, lp | 1.21M | 0.01% | 535.84K |
| Algert global | 445.81K | 0.07% | 397.66K |
Top Sellers
| Holder | Shares | % Assets | Change |
|---|---|---|---|
| Ecor1 capital | - | - | -11.58M |
| Adar1 capital management | 1.47M | 1.35% | -1.91M |
| Siren | - | - | -1.28M |
| Armistice capital | 439.41K | 0.08% | -1.06M |
| Finepoint capital lp | - | - | -640.07K |
New Positions
| Holder | Shares | % Assets | Change | Value |
|---|---|---|---|---|
| Penbrook management | 271.72K | 2.00% | 271.72K | $2.64M |
| Vanguard fiduciary trust | 254.57K | 0.00% | 254.57K | $2.47M |
| Norges bank | 57.45K | 0.00% | 57.45K | $795.74K |
| Jackson creek investment advisors | 54.09K | 0.15% | 54.09K | $526.00K |
| Winton group | 34.70K | 0.01% | 34.70K | $337.28K |
Sold Out
| Holder | Change |
|---|---|
| Koesten, hirschmann & crabtree | -1.00 |
| Truvestments capital | -1.00 |
| Cypress capital | -2.00 |
| Jfs wealth advisors | -2.00 |
| Cbiz investment advisory services | -2.00 |
Institutional Ownership Trends
| Date | Holdings | Change % | Shares | Change % | Ownership | Change % | Increased Position | Change % | Decreased Position | Change % |
|---|---|---|---|---|---|---|---|---|---|---|
| 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% |
| Mar 31, 2025 | 6 | -96.69% | 2,463,987 | -95.40% | 4 | 0.05% | 2 | -98.06% | 4 | -88.89% |
Top Mutual Funds Shareholders
| Holder | Shares | % Holding | Change |
|---|---|---|---|
| Vanguard Health Care Inv | 4.18M | 7.77% | -39.90K |
| Fidelity Growth Compy Commingled Pl S | 3.43M | 6.55% | 2.78K |
| Fidelity Growth Compy Commingled Pl O | 3.28M | 6.09% | 1.22K |
| Fidelity Growth Company Fund | 2.29M | 4.38% | - |
| T. Rowe Price New Horizons | 1.64M | 3.04% | -251.35K |
| US Small-Cap Growth II Equity Comp | 1.64M | 3.04% | -251.90K |
| State Street® SPDR® S&P® Biotech ETF | 1.07M | 2.04% | -11.03K |
| iShares Russell 2000 ETF | 1.05M | 2.01% | 8.84K |
| Fidelity Series Growth Company | 758.90K | 1.45% | - |
| Nuveen Quant Small Cap Equity R6 | 652.13K | 1.25% | - |
Recent Insider Transactions
| Date | Name | Role | Activity | Value |
|---|---|---|---|---|
| Jun 04, 2026 | SCULLY WILLIAM P | - | Buy | $465.30K |
| Jun 02, 2026 | SCULLY WILLIAM P | - | Buy | $471.30K |
| May 22, 2026 | SCULLY WILLIAM P | - | Buy | $981.30K |
| May 05, 2025 | EcoR1 Capital, LLC | - | Sell | $7.93M |
| May 02, 2025 | EcoR1 Capital, LLC | - | Sell | $27.74M |
Insider Transactions Trends
| Date | Buy | Sell |
|---|---|---|
| 2026 Q2 | 3 | - |
| 2026 Q1 | - | - |
| 2025 Q3 | - | - |
| 2025 Q2 | - | 3 |
| 2025 Q1 | 1 | - |
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