Prothena Corp
PRTA
181 hedge funds and large institutions have $452M invested in Prothena Corp in 2025 Q4 according to their latest regulatory filings, with 25 funds opening new positions, 62 increasing their positions, 57 reducing their positions, and 26 closing their positions.
8.64% more ownership
Funds ownership: 79.15% → 87.78% (+8.6%)
9% more capital invested
Capital invested by funds: $416M → $452M (+$35.8M)
9% more repeat investments, than reductions
Existing positions increased: 62 | Existing positions reduced: 57
4% less first-time investments, than exits
New positions opened: 25 | Existing positions closed: 26
3% less funds holding
Funds holding: 187 → 181 (-6)
16% less call options, than puts
Call options by funds: $6.74M | Put options by funds: $8.02M
50% less funds holding in top 10
Funds holding in top 10: 2 → 1 (-1)
Top Buyers
| Rank | Fund | Capital Flow |
|---|---|---|
| 1 |
RCMNY
Rubric Capital Management (New York)
New York
|
+$21.8M |
| 2 |
State Street
Boston,
Massachusetts
|
+$13.9M |
| 3 |
Goldman Sachs
New York
|
+$5.93M |
| 4 |
BlackRock
New York
|
+$5.18M |
| 5 |
Morgan Stanley
New York
|
+$4.55M |
Top Sellers
| Rank | Fund | Capital Flow |
|---|---|---|
| 1 |
Millennium Management
New York
|
-$6.1M |
| 2 |
JP Morgan Chase
New York
|
-$5.76M |
| 3 |
AG
Algert Global
San Francisco,
California
|
-$4.35M |
| 4 |
Arrowstreet Capital
Boston,
Massachusetts
|
-$3.63M |
| 5 |
Fidelity Investments
Boston,
Massachusetts
|
-$3.56M |
PRTA Hedge Fund Activity: Q4 2025 in Review
181 of the 8,267 institutional investors tracked by Wall St. Rank reported a position in Prothena Corp (PRTA) for Q4 2025, worth a combined $452M — up 8.6% from $416M a quarter earlier.
Sellers outnumbered buyers: 26 funds closed out of PRTA and 25 opened new positions — a net loss of 1 holder — while 57 trimmed existing stakes and 62 added.
The largest buyer was Rubric Capital Management (New York), adding an estimated $21.8M. The largest seller was Millennium Management, cutting an estimated $6.1M.
- 181 institutional investors held Prothena Corp (PRTA) as of Q4 2025, down from 187 in Q3 2025.
- Funds reported $452M of Prothena Corp stock for Q4 2025, up 8.6% quarter-over-quarter.
- 25 funds opened new Prothena Corp positions in Q4 2025 and 26 closed out, a net change of -1 holder.
- The largest Prothena Corp buyer in Q4 2025 was Rubric Capital Management (New York), an estimated $21.8M added.
- The largest Prothena Corp seller in Q4 2025 was Millennium Management, an estimated $6.1M sold.
Based on aggregated 13F filings for Q4 2025.