Welcome to our dedicated page for Atara Biotherape SEC filings (Ticker: ATRA), a comprehensive resource for investors and traders seeking official regulatory documents including 10-K annual reports, 10-Q quarterly earnings, 8-K material events, and insider trading forms.
Atara Biotherapeutics' SEC filings document the company's allogeneic EBV T-cell immunotherapy business, public common stock, and regulatory record for tabelecleucel, including 8-K disclosures tied to FDA communications, Complete Response Letter updates, and the EBVALLO Biologics License Application.
The filings also report financial results and liquidity updates, commercialization and milestone arrangements, amendments to royalty-related purchase and sale agreements, warrant issuance terms, Nasdaq continued-listing compliance notices, and proxy matters such as board elections, executive compensation, equity awards, and shareholder voting proposals.
HEIDEN WILLIAM K reported acquisition or exercise transactions in this Form 4 filing.
Atara Biotherapeutics director William K. Heiden received a grant of 12,000 shares of Common Stock in the form of restricted stock units as compensation. The award was recorded at a price of $0.00 per share and is not an open-market purchase.
These restricted stock units will vest on the earlier of June 9, 2027 or the date of the next annual meeting of stockholders, provided he maintains continuous service. Following this grant, Heiden directly holds 34,188 shares of Atara Biotherapeutics common stock.
Fust Matthew K reported acquisition or exercise transactions in this Form 4 filing.
Atara Biotherapeutics director Matthew K. Fust received an equity award of 12,000 shares of common stock in the form of restricted stock units. The award was granted at no cash cost and will vest on the earlier of June 9, 2027 or the next annual stockholder meeting, subject to his continuous service. Following this grant, he holds 30,188 shares directly.
Ciongoli Gregory Austin reported acquisition or exercise transactions in this Form 4 filing.
Atara Biotherapeutics director Gregory A. Ciongoli reported an equity compensation award and updated his indirect holdings. He received a grant of 12,000 shares of common stock as a restricted stock unit award at a price of $0.00 per share.
These restricted stock units vest on the earlier of June 9, 2027 or the date of the next annual meeting of stockholders, subject to his continuous service. The filing also reports 1,209,395 shares of common stock indirectly held by Adiumentum Capital Fund I LP, a Delaware limited partnership with which Ciongoli and its general partner are associated, while all parties disclaim beneficial ownership except to the extent of any pecuniary interest.
Atara Biotherapeutics President and CEO Nguyen AnhCo reported an automatic sale of common stock tied to equity compensation. On May 18, 2026, 5,241 shares of common stock were sold at a weighted average price of $9.1289 per share. According to the disclosure, the shares were sold automatically to satisfy tax withholding obligations triggered by the vesting of previously granted restricted stock units under a sale-to-cover provision, rather than as a discretionary open-market sale for portfolio reasons. Following this transaction, AnhCo directly holds 137,837 shares of Atara common stock.
Atara Biotherapeutics Chief Accounting Officer Yanina Grant-Huerta reported the sale of 2,414 shares of common stock. The shares were sold on May 18, 2026 at a weighted average price of $9.1286 per share, in multiple trades between $9.12 and $9.40.
According to the disclosure, these shares were sold automatically to satisfy tax withholding obligations tied to the vesting of previously granted restricted stock units under a sale-to-cover provision. After the transaction, Grant-Huerta directly holds 49,636 shares of Atara common stock.
ATRA submitted a notice for the settlement/sale of 13,887 shares of Common Stock on 05/15/2026, described as settlement of vested RSUs issued under an S-8 registration plan. The excerpt also shows a prior sale of 2,996 shares on 03/02/2026.
ATRA submitted a Form 144 notice reporting the settlement and disposition of Common Stock tied to employee equity. The filing shows 6,393 shares settled on 05/15/2026 as payment for vested RSUs issued under an S-8 registration, and a prior sale of 2,104 shares on 03/02/2026.
Redmile Group and related entities updated their ownership disclosure for Atara Biotherapeutics. They report beneficial ownership of 950,994 shares of common stock, representing 9.9% of the class, including shares issuable from pre-funded warrants subject to a 9.99% Beneficial Ownership Limitation.
The filing explains that this increase in deemed beneficial ownership results from a higher number of Atara shares outstanding, which raised the maximum shares issuable upon warrant exercise. Redmile-managed funds directly hold 441,701 common shares and 3,412,843 pre-funded warrants, of which 509,293 shares are currently counted toward beneficial ownership under the limitation.
Atara Biotherapeutics reports a reported 8.56% ownership position held by Adage Capital Management and affiliated individuals.
Adage Capital Management, L.P., together with Robert Atchinson and Phillip Gross, states shared dispositive and voting power over 700,000 shares of Common Stock. The filing calculates the percentage using 8,178,114 shares outstanding as of March 10, 2026. The statement is a joint Schedule 13G disclosure of beneficial ownership and identifies the Reporting Persons and their business addresses.
Atara Biotherapeutics amended its sales-agreement prospectus to confirm it may continue at-the-market sales up to an aggregate offering price of $79,269,007 under the existing Sales Agreement with TD Securities (USA) LLC. This supplement, dated May 12, 2026, relies on a staff interpretation addressing Form S-3 eligibility after a Section 10(a)(3) update.
The supplement states the company may offer and sell shares of Common Stock from time to time through the named sales agent, and that the full amount remaining under the Sales Agreement is available despite a change in the Form S-3 eligibility criterion referenced in General Instruction I.B.1 because the company qualifies under General Instruction I.B.6.