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SCHEDULE Filed 2025-01-03 Event 2024-12-31 SEC 0000935836-25-000018 →

EcoR1 Capital, LLC PROTHENA CORP PUBLIC LTD CO PRTA

Stake: 21.50% Shares: 11,584,280 CUSIP: G72800108 Class: Ordinary Shares

Item 4 — Purpose of Transaction

The reporting persons filed this Schedule 13D because the Issuer's board of directors appointed Oleg Nodelman to serve as a director of the Issuer. On December 31, 2024, Mr. Nodelman resigned from the Issuer's board of directors. The reporting persons acquired Ordinary Shares for investment purposes based on their belief that the Issuer's Ordinary Shares, when purchased, was undervalued and represented an attractive investment opportunity. The reporting persons will routinely monitor the Issuer regarding a wide variety of factors that affect their investment considerations, including, current and anticipated future trading prices of the Ordinary Shares and other securities, the Issuer's operations, assets, prospects, financial position, and business development, Issuer's management, Issuer-related competitive and strategic matters, general economic, financial market and industry conditions, and other investment considerations. Depending on their evaluation of various factors, the reporting persons may take such actions regarding their holdings of the Issuer's securities as they deem appropriate in light of circumstances existing from time to time. Such actions may include purchasing additional Ordinary Shares in the open market, through privately negotiated transactions with third parties or otherwise, and selling at any time, in the open market, through privately negotiated transactions with third parties or otherwise, all or part of the Ordinary Shares that they now own or hereafter acquire. The reporting persons also may from time to time enter into or unwind hedging or other derivative transactions with respect to the Ordinary Shares or pledge their interests in the Ordinary Shares to obtain liquidity. In addition, from time to time the reporting persons and their representatives and advisers may communicate with other stockholders, industry participants and other interested parties about the Issuer. The reporting persons have no present plan or proposal that relates to or would result in any of the actions specified in clauses (a) through (j) of Item 4 of Schedule 13D. However, the reporting persons may recommend action to the Issuer's management, board of directors and stockholders. Any such actions could involve one or more of the events referred to in clauses (a) through (j) of Item 4 of Schedule 13D, including, potentially, one or more mergers, consolidations, sales or acquisitions of assets, changes in control, issuances, purchases, dispositions or pledges of securities or other changes in capitalization.

Cross-References

Insider Activity (last 365d)
19 transactions
8 buys · 5 sales · 5 awards/exercises
Issuer Cluster
2 13D/G filings on this issuer
1 other filing besides this one
Filer Track Record
13 filings by this filer
12 other filings in the data moat
Short Interest · settle 2026-07-15
DTC 16.40
8,196,964 shares short · -2.1% vs prior

Institutional Consensus · 2025-12-31

Held by elite portfolio managers
1 holder · $8.78M
Point72 Asset Mgmt

Post-Filing Returns · since 2024-12-31 on PRTA

+1 day
0.0%
+5 days
0.0%
+30 days
0.0%
+60 days
0.0%
+90 days
0.0%
+180 days
0.0%

Anchor price 9.68 on closest trading day on/after 2024-12-31. Source: Yahoo Finance daily adj_close (split + dividend adjusted).

Form 4 Insider Transactions · last 365d

DateInsiderRoleTypeSharesPriceValue
2026-07-28 Zago Wagner M. officer Option exercise 51,000
2026-07-28 Zago Wagner M. officer Disposition 51,000 $8.56 $437K
2026-07-28 Walker Karin L officer Option exercise 15,000
2026-07-28 Walker Karin L officer Disposition 15,000 $8.56 $128K
2026-07-28 Swanson Chad J. officer Option exercise 51,000
2026-07-28 Swanson Chad J. officer Disposition 40,800 $8.56 $349K
2026-07-28 Swanson Chad J. officer F 3,467 $8.56 $30K
2026-07-28 Smith Brandon S. officer Option exercise 78,000
2026-07-28 Smith Brandon S. officer Disposition 78,000 $8.56 $668K
2026-07-28 Nguyen Tran officer Option exercise 57,000
2026-07-28 Nguyen Tran officer Disposition 57,000 $8.56 $488K
2026-06-04 SCULLY WILLIAM P 10%+ owner Buy 50,000 $9.31 $465K
2026-05-15 WELCH DANIEL G director Award 27,000 $9.76 $264K
2026-05-15 Selkoe Dennis J. director Award 27,000 $9.76 $264K
2026-05-15 Ekman Lars director Award 27,000 $9.76 $264K
2026-05-15 Dunn William H. Jr. director Award 27,000 $9.76 $264K
2026-05-15 Cooke Shane director Award 27,000 $9.76 $264K
2026-05-15 COLLIER RICHARD T director Award 27,000 $9.76 $264K
2026-04-10 Kingston Anne Evans officer Award 100,000 $10.50 $1.05M

Other 13D/G Filings on PROTHENA CORP PUBLIC LTD CO

FiledFormFilerStakeShares
2022-01-14 SC EcoR1 Capital, LLC view →

Other Filings by EcoR1 Capital, LLC

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2026-06-16 SCHEDULE 13G Eloxx Pharmaceuticals, Inc. ELOX view →
2025-05-19 SCHEDULE GALAPAGOS NV GLPGF 11.84% 7,803,202 view →
2025-03-17 SCHEDULE Zymeworks Inc. ZYME 24.20% 16,858,418 view →
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2025-01-13 SCHEDULE Zymeworks Inc. ZYME 22.40% 15,411,078 view →
2024-10-08 SC GALAPAGOS NV GLPGF view →
2022-01-14 SC PROTHENA CORP PUBLIC LTD CO PRTA view →
2021-05-11 SC ANAPTYSBIO, INC ANABV view →
2021-04-13 SC ANAPTYSBIO, INC ANABV view →

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