Prothena Corporation plc
Prothena Corporation plc (PRTA) Stock Ownership
Institutional vs insider vs public ownership from 13F and float data — top holders, activity, and insider trades below.
SEC 13F · FMP · PRTA · as of Sep 30, 2025
Ownership Breakdown
201
Institutional Holders
▼ 1 vs Q2
$416.06M
Total Inst. Value
▲ $162.45M vs Q2
52.35M
Shares Outstanding
freeFloat 88.31%
42.64M
13F Shares Held
▲ 863,034 vs Q2
Institutional ownership = 13F shares ÷ total outstanding. Insider % = 100 − free float. Public % = free float − institution %. Data: FMP /symbol-positions-summary + /shares-float + SEC EDGAR.
Top Institutional Holders
PRTA largest shareholders · institutional ownership
Q3 2025 · SEC 13F
Showing top 10 holders
| Holder | Shares | % Owned | Weight | Value | Reported | Change |
|---|---|---|---|---|---|---|
FMR LLC pharmaceutical preparations | 7.90M | 14.68% | 14.68% | $77.12B | Nov 13, 2025 | — held |
BLACKROCK, INC. pharmaceutical preparations | 3.60M | 6.69% | 6.69% | $35.12B | Nov 12, 2025 | ▼ 341.0K |
VANGUARD GROUP INC pharmaceutical preparations | 2.05M | 3.81% | 3.81% | $20.01B | Nov 7, 2025 | ▼ 126.4K |
ARMISTICE CAPITAL, LLC pharmaceutical preparations | 1.82M | 3.39% | 3.39% | $17.80B | Nov 17, 2025 | ▼ 412.0K |
RUBRIC CAPITAL MANAGEMENT LP pharmaceutical preparations | 1.54M | 2.86% | 2.86% | $15.03B | Nov 14, 2025 | NEW |
ADAR1 CAPITAL MANAGEMENT, LLC pharmaceutical preparations | 1.47M | 2.73% | 2.73% | $14.34B | Nov 14, 2025 | ▼ 1.91M |
PALO ALTO INVESTORS LP pharmaceutical preparations | 1.32M | 2.46% | 2.46% | $12.92B | Nov 14, 2025 | ▲ 49.3K |
D. E. SHAW & CO., INC. pharmaceutical preparations | 1.32M | 2.44% | 2.44% | $12.84B | Nov 14, 2025 | ▲ 923.9K |
ACADIAN ASSET MANAGEMENT LLC pharmaceutical preparations | 1.24M | 2.30% | 2.30% | $12.09B | Nov 13, 2025 | ▲ 221.1K |
GEODE CAPITAL MANAGEMENT, LLC pharmaceutical preparations | 1.02M | 1.89% | 1.89% | $9.95B | Nov 12, 2025 | ▲ 86.0K |
Data from SEC Form 13F filings. Ownership bar normalised to largest holder. Change flags: isNew / isSoldOut / changeInSharesNumber (FMP extract-analytics/holder).
Institutional Activity
Q3 2025 vs prior quarter
Q3 2025
28
Increased
+6.15M shares5
New Positions
first time holders16
Decreased
−5.19M shares0
Sold Out
fully exitedNet shares change (top 50)
+963.4K
+6.15M / −5.19M
Net new holders
+17
5 new / 0 exited
Based on top 50 institutional holders by position size. Fields: isNew, isSoldOut, changeInSharesNumber (FMP extract-analytics/holder, limit=50).
Insider Buying vs Selling
PRTA insider trading · insider activity
Source: SEC Form 4
Insiders have been net buyers of shares recently. Selling may be driven by pre-scheduled Rule 10b5-1 plans rather than negative sentiment.
10
Buy transactions
0
Sell transactions
0.00
Buy/Sell ratio
$0M
Total disposed
Recent Insider Transactions
Showing 10 most recent · Common Stock only
| Name · Role | Date | Type | Shares | Price | Value | After Trans. | Filing |
|---|---|---|---|---|---|---|---|
SCULLY WILLIAM P 10 percent owner | Jun 4, 2026 | Purchase | 50,000 | $9.31 | $465.3K | 936.0K | Form 4 ↗ |
SCULLY WILLIAM P 10 percent owner | Jun 2, 2026 | Purchase | 50,000 | $9.43 | $471.3K | 886.0K | Form 4 ↗ |
SCULLY WILLIAM P 10 percent owner | May 22, 2026 | Purchase | 100,000 | $9.81 | $981.3K | 836.0K | Form 4 ↗ |
WELCH DANIEL G director | May 15, 2026 | Award | 27,000 | $9.76 | $263.5K | 27.0K | Form 4 ↗ |
Selkoe Dennis J. director | May 15, 2026 | Award | 27,000 | $9.76 | $263.5K | 27.0K | Form 4 ↗ |
Ekman Lars director | May 15, 2026 | Award | 27,000 | $9.76 | $263.5K | 27.0K | Form 4 ↗ |
Dunn William H. Jr. director | May 15, 2026 | Award | 27,000 | $9.76 | $263.5K | 27.0K | Form 4 ↗ |
Cooke Shane director | May 15, 2026 | Award | 27,000 | $9.76 | $263.5K | 27.0K | Form 4 ↗ |
COLLIER RICHARD T director | May 15, 2026 | Award | 27,000 | $9.76 | $263.5K | 27.0K | Form 4 ↗ |
Kingston Anne Evans Chief Strategy Officer | Apr 10, 2026 | Award | 100,000 | $10.50 | $1.05M | 100.0K | Form 4 ↗ |
Source: /insider-trading/search (FMP stable). Buy/Sell direction: acquisitionOrDisposition A=Buy, D=Sell. RSU vesting (M-Exempt) excluded from sentiment bar. All data from SEC EDGAR public filings.
About institutional & insider ownership
Prothena Corporation plc (PRTA) is primarily owned by institutional investors, who hold approximately 81.5% of total shares outstanding. Company insiders own approximately 11.69%, while retail and public investors account for the remaining 6.87%.
The largest institutional shareholder of Prothena Corporation plc is FMR LLC, holding approximately 7.90 million shares — equal to 14.68% of outstanding shares — as of September 30, 2025.
A total of 201 institutional investors currently hold PRTA stock, with a combined institutional value of approximately $416,062,605 as of the most recent 13F filing period.
Frequently asked questions
PRTA ownershipProthena Corporation plc (PRTA) is primarily owned by institutional investors, who hold approximately 81.5% of shares. The largest shareholder is FMR LLC with a 14.68% stake. Company insiders hold 11.69%. Data sourced from SEC Form 13F as of September 30, 2025.