Prothena Corp
PRTA
188 hedge funds and large institutions have $254M invested in Prothena Corp in 2025 Q2 according to their latest regulatory filings, with 51 funds opening new positions, 54 increasing their positions, 40 reducing their positions, and 23 closing their positions.
122% more first-time investments, than exits
New positions opened: 51 | Existing positions closed: 23
35% more repeat investments, than reductions
Existing positions increased: 54 | Existing positions reduced: 40
17% more funds holding
Funds holding: 161 → 188 (+27)
6% more call options, than puts
Call options by funds: $6.7M | Put options by funds: $6.34M
0% more funds holding in top 10
Funds holding in top 10: 3 → 3 (0)
19.59% less ownership
Funds ownership: 97.18% → 77.59% (-20%)
61% less capital invested
Capital invested by funds: $647M → $254M (-$394M)
Top Buyers
| Rank | Fund | Capital Flow |
|---|---|---|
| 1 |
ACM
ADAR1 Capital Management
Austin,
Texas
|
+$25.3M |
| 2 |
Citadel Advisors
Miami,
Florida
|
+$7.94M |
| 3 |
Acadian Asset Management
Boston,
Massachusetts
|
+$7.64M |
| 4 |
Vanguard Group
Malvern,
Pennsylvania
|
+$6.81M |
| 5 |
RC
Rangeley Capital
New Canaan,
Connecticut
|
+$5.37M |
Top Sellers
| Rank | Fund | Capital Flow |
|---|---|---|
| 1 |
EC
EcoR1 Capital
San Francisco,
California
|
-$143M |
| 2 |
Wellington Management Group
Boston,
Massachusetts
|
-$38.2M |
| 3 |
T. Rowe Price Associates
Baltimore,
Maryland
|
-$25.4M |
| 4 |
SL
Siren LLC
Greenwich,
Connecticut
|
-$15.9M |
| 5 |
BCM
Boxer Capital Management
San Diego,
California
|
-$8.54M |
PRTA Hedge Fund Activity: Q2 2025 in Review
188 of the 7,596 institutional investors tracked by Wall St. Rank reported a position in Prothena Corp (PRTA) for Q2 2025, worth a combined $254M — down 61% from $647M a quarter earlier.
Buyers outnumbered sellers: 51 funds opened new PRTA positions and 23 closed out — a net gain of 28 holders — while 54 added to existing stakes and 40 trimmed.
The largest buyer was ADAR1 Capital Management, opening a new position worth an estimated $25.3M. The largest seller was EcoR1 Capital, exiting entirely with an estimated $143M sold.
- 188 institutional investors held Prothena Corp (PRTA) as of Q2 2025, up from 161 in Q1 2025.
- Funds reported $254M of Prothena Corp stock for Q2 2025, down 61% quarter-over-quarter.
- 51 funds opened new Prothena Corp positions in Q2 2025 and 23 closed out, a net change of +28 holders.
- The largest Prothena Corp buyer in Q2 2025 was ADAR1 Capital Management, an estimated $25.3M added.
- The largest Prothena Corp seller in Q2 2025 was EcoR1 Capital, an estimated $143M sold.
Based on aggregated 13F filings for Q2 2025.