EcoR1 Capital, LLC 4
4 · Atara Biotherapeutics, Inc. · Filed May 11, 2026
Research Summary
AI-generated summary of this filing
Atara Biotherapeutics (ATRA) 10% Owner EcoR1 Capital Buys 507,407 Shares
What Happened
EcoR1 Capital, LLC (reported as a 10% owner) reported an open-market purchase of 507,407 shares of Atara Biotherapeutics (ATRA) on 2026-05-07 at a weighted average price of $9.35, for a total reported value of $4,744,255. The filing notes that EcoR1 is the adviser and general partner to funds that hold the shares and that the purchases were made for those funds rather than by an individual executive.
Key Details
- Transaction date: 2026-05-07 (reported on Form 4 filed 2026-05-11)
- Transaction type/code: Purchase (open market) — Code P
- Shares purchased: 507,407
- Weighted average price: $9.35; price range across trades $8.85–$9.39 (reporting person will provide per-price breakdown on request)
- Total value: $4,744,255
- Purchaser breakdown: Qualified Fund (EcoR1 Capital Fund Qualified, L.P.) bought 474,780 of the shares (F2)
- Holdings after transaction: Qualified Fund held 1,445,609 shares (F4)
- Reporting persons: EcoR1 Capital, LLC; Oleg Nodelman; and EcoR1 Capital Fund Qualified, L.P. (F1). They filed jointly but disclaim membership in a group and disclaim beneficial ownership except to the extent of pecuniary interest.
- Filing timeliness: Form 4 filed on 2026-05-11 — appears timely (filed within the required period following the 2026-05-07 transaction).
Context
This is an institutional purchase by a reported 10% owner/adviser-managed fund, not an individual executive. Purchases by funds can reflect portfolio activity rather than a personal view; the filing discloses the fund-level ownership and provides a price-range breakdown on request for further detail.
Insider Transaction Report
- Purchase
Common Stock
[F2][F3][F4][F1]2026-05-07$9.35/sh+507,407$4,744,255→ 1,552,000 total(indirect: See Note)
Footnotes (4)
- [F1]The reporting persons are EcoR1 Capital, LLC ("EcoR1"), Oleg Nodelman and EcoR1 Capital Fund Qualified, L.P. ("Qualified Fund"). EcoR1 is the general partner and investment adviser of private funds, including Qualified Fund (the "Funds"). Mr. Nodelman is the manager and controller owner of EcoR1. EcoR1 is filing this Form 4 for itself, Mr. Nodelman and Qualified Fund. The reporting persons are filing this Form 4 jointly, but not as a group, and each expressly disclaims membership in a group within the meaning of Rule 13d-5(b) under the Securities Exchange Act of 1934. The Funds hold these securities directly for the benefit of their investors. EcoR1 may be deemed to indirectly beneficially own them as the investment adviser to the Funds. Mr. Nodelman may be deemed to indirectly beneficially own them as the control person of EcoR1. The reporting persons disclaim beneficial ownership of the securities except to the extent of their respective pecuniary interests therein.
- [F2]Qualified Fund purchased 474,780 of the shares puchased in this transaction.
- [F3]The price reported in Column 4 is a weighted average price. These shares were purchased in multiple transactions at prices ranging from $8.85 to $9.39 inclusive. The reporting person undertakes to provide to the Issuer, any security holder of the Issuer, or the staff of the Securities and Exchange Commission upon request, full information regarding the number of shares purchased at each separate price within the ranges set forth in this footnote.
- [F4]After this transaction, Qualified Fund held 1,445,609 shares of the Issuer's Common Stock.