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EcoR1 Capital’s Prothena Corp PRTA Stock Holding History

EcoR1 Capital’s Portfolio PRTA Stock Details PRTA Fund Activity
Bought
Maintained
Sold
Quarter Market Value Status Shares Change in
Stake 		Trade Value Portfolio Weight Portfolio Position
2025
Q2 		– Sell
-11,584,280
Closed -$143M – 45
2025
Q1 		$143M Hold
11,584,280
– – 8.5% 6
2024
Q4 		$160M Hold
11,584,280
– – 6.07% 5
2024
Q3 		$194M Hold
11,584,280
– – 6.63% 4
2024
Q2 		$239M Hold
11,584,280
– – 7.31% 2
2024
Q1 		$287M Hold
11,584,280
– – 7.26% 2
2023
Q4 		$421M Hold
11,584,280
– – 10.93% 3
2023
Q3 		$559M Hold
11,584,280
– – 18.85% 1
2023
Q2 		$791M Hold
11,584,280
– – 19.38% 1
2023
Q1 		$561M Hold
11,584,280
– – 18.08% 1
2022
Q4 		$698M Hold
11,584,280
– – 21.24% 1
2022
Q3 		$702M Hold
11,584,280
– – 20.73% 1
2022
Q2 		$315M Hold
11,584,280
– – 10.86% 1
2022
Q1 		$424M Buy
11,584,280
+300,000
+3% +$10.8M 13.25% 1
2021
Q4 		$557M Hold
11,284,280
– – 17.76% 1
2021
Q3 		$804M Hold
11,284,280
– – 27.96% 1
2021
Q2 		$580M Buy
11,284,280
+250,000
+2% +$7.8M 21.68% 1
2021
Q1 		$277M Buy
11,034,280
+1,607,640
+17% +$30.2M 12.29% 1
2020
Q4 		$113M Hold
9,426,640
– – 6.09% 5
2020
Q3 		$94.2M Hold
9,426,640
– – 6.71% 4
2020
Q2 		$98.6M Hold
9,426,640
– – 7.28% 2
2020
Q1 		$101M Hold
9,426,640
– – 10.54% 1
2019
Q4 		$149M Hold
9,426,640
– – 13.45% 1
2019
Q3 		$73.9M Buy
9,426,640
+8,703,340
+1,203% +$77.3M 9.33% 2
2019
Q2 		$7.64M Sell
723,300
-3,219
-0.4% -$33.1K 0.77% 23
2019
Q1 		$8.81M Sell
726,519
-111,700
-13% -$1.39M 0.81% 30
2018
Q4 		$8.63M Buy
+838,219
New +$9.96M 0.86% 35

Other funds holding PRTA

Fidelity Investments
Fidelity Investments Boston, Massachusetts $1.9T AUM 41.92% 1-Year Est. Return
BlackRock
BlackRock New York $5.72T AUM 30.48% 1-Year Est. Return
ACM
ADAR1 Capital Management Austin, Texas $1.7B AUM 340.85% 1-Year Est. Return
AC
Armistice Capital New York $5.62B AUM 36.06% 1-Year Est. Return
Vanguard Group
Vanguard Group Malvern, Pennsylvania $6.9T AUM 27.45% 1-Year Est. Return
PAI
Palo Alto Investors Palo Alto, California $654M AUM 77.8% 1-Year Est. Return
Federated Hermes
Federated Hermes Pittsburgh, Pennsylvania $61.5B AUM 30.7% 1-Year Est. Return
Citadel Advisors
Citadel Advisors Miami, Florida $618B AUM 30.34% 1-Year Est. Return
Acadian Asset Management
Acadian Asset Management Boston, Massachusetts $70.5B AUM 36% 1-Year Est. Return
State Street
State Street Boston, Massachusetts $2.9T AUM 29.55% 1-Year Est. Return

EcoR1 Capital's PRTA Position: Q2 2025 in Review

EcoR1 Capital sold out of Prothena Corp (PRTA) in Q2 2025, closing a stake of 11,584,280 shares — an estimated $143M sold.

EcoR1 Capital first reported a position in PRTA in Q4 2018 and held it in 26 quarters. The position peaked at $804M in Q3 2021. 188 funds tracked by Wall St. Rank hold PRTA as of Q2 2025.

  • EcoR1 Capital reported no remaining Prothena Corp position as of Q2 2025 after selling out during the quarter.
  • EcoR1 Capital sold 11,584,280 Prothena Corp shares in Q2 2025, an estimated $143M.
  • EcoR1 Capital first reported a position in Prothena Corp in Q4 2018 and held it in 26 quarters.
  • EcoR1 Capital's Prothena Corp position peaked at $804M in Q3 2021.
  • 188 funds tracked by Wall St. Rank held Prothena Corp as of Q2 2025.

Based on EcoR1 Capital's 13F filing for Q2 2025, filed 14 Aug 2025.