Prothena Corp
PRTA
187 hedge funds and large institutions have $416M invested in Prothena Corp in 2025 Q3 according to their latest regulatory filings, with 32 funds opening new positions, 57 increasing their positions, 61 reducing their positions, and 33 closing their positions.
64% more capital invested
Capital invested by funds: $254M → $416M (+$162M)
1.55% more ownership
Funds ownership: 77.59% → 79.15% (+1.6%)
1% less funds holding
Funds holding: 188 → 187 (-1)
3% less first-time investments, than exits
New positions opened: 32 | Existing positions closed: 33
7% less repeat investments, than reductions
Existing positions increased: 57 | Existing positions reduced: 61
33% less funds holding in top 10
Funds holding in top 10: 3 → 2 (-1)
50% less call options, than puts
Call options by funds: $7.5M | Put options by funds: $15.1M
Top Buyers
| Rank | Fund | Capital Flow |
|---|---|---|
| 1 |
RCMNY
Rubric Capital Management (New York)
New York
|
+$11.8M |
| 2 |
D.E. Shaw & Co
New York
|
+$7.1M |
| 3 |
Arrowstreet Capital
Boston,
Massachusetts
|
+$5.03M |
| 4 |
Point72 Asset Management
Stamford,
Connecticut
|
+$4.97M |
| 5 |
JP Morgan Chase
New York
|
+$4.68M |
Top Sellers
| Rank | Fund | Capital Flow |
|---|---|---|
| 1 |
ACM
ADAR1 Capital Management
Austin,
Texas
|
-$14.6M |
| 2 |
Balyasny Asset Management
Chicago,
Illinois
|
-$4M |
| 3 |
Federated Hermes
Pittsburgh,
Pennsylvania
|
-$3.75M |
| 4 |
RSCM
Rock Springs Capital Management
Baltimore,
Maryland
|
-$3.59M |
| 5 |
AC
Armistice Capital
New York
|
-$3.17M |
PRTA Hedge Fund Activity: Q3 2025 in Review
187 of the 7,619 institutional investors tracked by Wall St. Rank reported a position in Prothena Corp (PRTA) for Q3 2025, worth a combined $416M — up 64% from $254M a quarter earlier.
Sellers outnumbered buyers: 33 funds closed out of PRTA and 32 opened new positions — a net loss of 1 holder — while 61 trimmed existing stakes and 57 added.
The largest buyer was Rubric Capital Management (New York), opening a new position worth an estimated $11.8M. The largest seller was ADAR1 Capital Management, cutting an estimated $14.6M.
- 187 institutional investors held Prothena Corp (PRTA) as of Q3 2025, down from 188 in Q2 2025.
- Funds reported $416M of Prothena Corp stock for Q3 2025, up 64% quarter-over-quarter.
- 32 funds opened new Prothena Corp positions in Q3 2025 and 33 closed out, a net change of -1 holder.
- The largest Prothena Corp buyer in Q3 2025 was Rubric Capital Management (New York), an estimated $11.8M added.
- The largest Prothena Corp seller in Q3 2025 was ADAR1 Capital Management, an estimated $14.6M sold.
Based on aggregated 13F filings for Q3 2025.