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PROTHENA CORP PUBLIC LTD CO
PRTA
Amendment
Ownership

0.00%

Total Shares

0

Issuer CIK

1559053

CUSIP

G72800108

Event Date

May 26, 2025

Accepted

May 29, 2025, 09:08 PM

SEC EDGARView Original Filing
Reporting Persons (3)
Joint Filing

This is a joint filing. The reported shares may overlap between reporting persons and should not be summed.

NameType% of ClassAggregateSole VotingShared Voting
EcoR1 Capital, LLC
Investment Adviser
0.00%000
Oleg Nodelman
Individual
0.00%000
EcoR1 Capital Fund Qualified, L.P.
Partnership
0.00%000
Disclosure Items (7)

Security Title

Ordinary Shares

Issuer Name

PROTHENA CORP PUBLIC LTD CO

Issuer Address

77 SIR JOHN ROGERSON'S QUAY, BLOCK C, Dublin 2, L2, D02 VK60

Filing Persons

The reporting persons are: EcoR1 Capital, LLC, a Delaware limited liability company ("EcoR1") EcoR1 Capital Fund Qualified, L.P., a Delaware limited partnership ("Qualified Fund") Oleg Nodelman Qualified Fund is filing this statement jointly with the other reporting persons, but not as a member of a group, and it expressly disclaims membership in a group. In addition, the filing of this Schedule 13D on behalf of Qualified Fund should not be construed as an admission that it is, and it disclaims that it is, a beneficial owner, as defined in Rule 13d-3 under the Act, of any securities covered by this Schedule 13D. Each reporting person also disclaims beneficial ownership of the securities reported herein except to the extent of that person's pecuniary interest therein.

Business Address

357 Tehama Street #3, San Francisco, CA 94103

Principal Occupation

EcoR1 is an investment adviser to investment funds, including Qualified Fund (collectively, the "Funds"). EcoR1 is the general partner of the Funds. Mr. Nodelman is the manager and control person of EcoR1.

Convictions

During the last five years, none of the reporting persons was a party to a civil proceeding of a judicial or administrative body of competent jurisdiction and as a result of such proceeding was or is subject to a judgment, decree or final order enjoining future violations of, or prohibiting or mandating activities subject to, federal or state securities laws or finding any violation with respect to such laws.

Citizenship

For citizenship of the reporting persons, see Item 6 of each reporting person's cover page.

The Funds used their working capital to purchase the Issuer's Ordinary Shares.

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.

Percentage of Class

Aggregate number of shares beneficially owned by the reporting persons: EcoR1: 0 Oleg Nodelman: 0 Qualified Fund: 0 Aggregate percentage of the class of Ordinary Shares beneficially owned by the reporting persons: EcoR1: 0.0% Oleg Nodelman: 0.0% Qualified Fund: 0.0%

Number of Shares

Number of shares as to which the each reporting person has: (i) Sole power to vote or to direct the vote: EcoR1: 0 Qualified Fund: 0 Oleg Nodelman: 0 (ii) Shared power to vote or to direct the vote: EcoR1: 0 Oleg Nodelman: 0 Qualified Fund: 0 (iii) Sole power to dispose or to direct the disposition of: EcoR1: 0 Qualified Fund: 0 Oleg Nodelman: 0 (iv) Shared power to dispose or to direct the disposition of: EcoR1: 0 Oleg Nodelman: 0 Qualified Fund: 0

Transactions

The reporting persons have engaged in the following transactions in the Issuer's Ordinary Shares in the 60 days preceding the date of this Schedule 13D: On 5/23/2025, the Funds sold 360,679 of the Issuer's Ordinary Shares for a dollar-weighted average price of $5.0357 per share. Qualified Fund sold 338,101 of these shares. On 5/27/2025, the Funds sold 466,668 of the Issuer's Ordinary Shares for a dollar-weighted average price of $4.7467 per share. Qualified Fund sold 437,453 of these shares. On 5/27/2025, the Funds sold 1,400,000 of the Issuer's Ordinary Shares for a dollar-weighted average price of $7.2708 per share. Qualified Fund sold 1,312,354 of these shares. On 5/28/2025, the Funds sold 509,000 of the Issuer's Ordinary Shares for a dollar-weighted average price of $4.6492 per share. Qualified Fund sold 477,140 of these shares. On 5/29/2025, the Funds sold 2,568,249 of the Issuer's Ordinary Shares for a dollar-weighted average price of $4.7410 per share. Qualified Fund sold 2,408,843 of these shares.

Shareholders

Not applicable.

Date of 5% Ownership

On May 28, 2025, each of the reporting persons ceased to be the beneficial owner of more than five percent of the outstanding shares.

EcoR1 is the investment adviser to its clients pursuant to investment management agreements or limited partnership agreements providing to EcoR1 the authority, among other things, to invest the funds of such clients in Ordinary Shares, to vote and dispose of Ordinary Shares and to file this statement on behalf of such clients. Pursuant to such limited partnership agreements, EcoR1 is entitled to allocations based on assets under management and realized and unrealized gains. Pursuant to such investment management agreements, EcoR1 is entitled to fees based on assets under management and realized and unrealized gains.

Exhibit 99.1 Agreement Regarding Joint Filing of Statement on Schedule 13D or 13G.

PROTHENA CORP PUBLIC LTD CO — Schedule 13D | 13D Filings