Atara Biotherapeutics, Inc. (ATRA) SEC Filings, Mar-May 2026

EcoR1 Capital and related filers reported passive ownership stakes in Atara Biotherapeutics. The filing shows EcoR1 Capital, LLC and Oleg Nodelman each report 1,552,000 shares (representing 17.4% of the class) and EcoR1 Capital Fund Qualified, L.P. reports 1,445,609 shares (16.2%), based on 8,912,272 shares outstanding as of May 7, 2026. The filing states excluded warrants to acquire 1,090,922 and 1,026,558 shares respectively that are subject to a 9.99% beneficial ownership limitation and currently cannot be exercised.

Atara Biotherapeutics reported a regulatory update on tabelecleucel (tab-cel) after a recent Type A meeting with the FDA following the Complete Response Letter issued on January 9, 2026 for its Biologics License Application held by partner Pierre Fabre Pharmaceuticals.

The FDA agreed that a single-arm study using an appropriate pre-specified historical control could be considered an adequate and well-controlled study to provide safety and efficacy data for a future marketing application in relapsed or refractory EBV+ PTLD after transplant in patients two years of age and older.

Pierre Fabre plans to submit an updated dataset with additional patients and longer follow-up from the pivotal Phase 3 ALLELE study, along with supportive data, as part of a resubmission plan being defined with the FDA. Atara expects to provide a further regulatory update in the third quarter.

Atara Biotherapeutics, Inc. received a Nasdaq notice that it no longer meets the $50 million minimum market value of listed securities (MVLS) required for continued listing on the Nasdaq Global Select Market.

Nasdaq reviewed the company’s market value over the last 30 consecutive business days and found it below this threshold. Atara has until October 27, 2026 (a 180-day compliance period) to regain compliance. If its MVLS closes at or above $50 million for at least 10 consecutive business days (and potentially up to 20 days at Nasdaq’s discretion), Nasdaq will confirm renewed compliance. The company’s shares continue trading under the symbol “ATRA” while it evaluates options, which may include applying to transfer to the Nasdaq Capital Market. If compliance is not regained by the deadline, Nasdaq may move to delist the shares, a decision Atara could appeal to a Hearings Panel.

Atara Biotherapeutics is asking stockholders to vote at its virtual 2026 annual meeting on June 9, 2026. Holders of 8,512,272 shares of common stock as of April 14, 2026 can participate online using a 16-digit control number.

Stockholders will elect two directors to terms ending in 2029, cast an advisory vote on named executive officer compensation, and vote on amending the 2024 Equity Incentive Plan to add 400,000 shares to the reserve, bringing total availability to 469,657 shares. They will also vote on ratifying Deloitte & Touche LLP as independent auditor for 2026. The proxy explains virtual meeting logistics, quorum and voting standards, broker non-votes, and outlines Atara’s board structure, independence, ESG oversight, cybersecurity framework and key governance policies, including stock ownership guidelines, clawback and anti-hedging rules.

Atara Biotherapeutics is registering for resale up to 400,000 shares of its common stock by HCR Molag Fund, L.P.

The shares are issuable upon exercise of a warrant that Atara issued under an amendment dated February 20, 2026 and are being registered to satisfy a covenant in that Warrant. The company will receive no proceeds from sales by the selling stockholder; Atara may receive proceeds only if the Warrant is exercised. The filing states 8,178,114 shares outstanding as of March 10, 2026 and a Beneficial Ownership Limitation that prevents exercise to the extent it would cause ownership above 4.99% (subject to increase up to 19.99% with notice and a 61‑day delay). Atara’s common stock is listed on Nasdaq and the last reported sale price in the prospectus was $6.50.

Atara Biotherapeutics, Inc. reported an insider transaction in which entities associated with Panacea funds exercised warrants to acquire common stock indirectly. Panacea Opportunity Fund I, L.P. exercised 259,163 warrants at an exercise price of $0.0001 per share, converting them into the same number of Atara common shares.

In connection with this exercise, 5 common shares were withheld at a price of $5.23 per share to cover tax obligations, a non-market disposition. Following these transactions, indirect holdings reported for these affiliated entities totaled over one million Atara common shares, while the reporting persons formally disclaim beneficial ownership beyond what may be attributed through their roles.

Atara Biotherapeutics, Inc. is registering for resale up to 400,000 shares of its common stock. These shares are issuable upon exercise of a warrant held by HCR Molag Fund, L.P., and the registration satisfies a covenant in that warrant.

Atara will receive no proceeds from resales; any proceeds go to the selling stockholder. The filing notes a Beneficial Ownership Limitation of 4.99% under the warrant, which may be adjusted up to 19.99% with notice.

Shares outstanding were 8,178,114 as of March 10, 2026. The prospectus permits public or private resale methods, hedging, short sales and transfers by successors-in-interest.

Atara Biotherapeutics registers the offer and sale of up to $11,135,981 of its common stock under a sales agreement with TD Securities (USA) LLC.

The Supplement states the offering is being made pursuant to General Instruction I.B.6 of Form S-3 and is limited by the companys aggregate market value of non-affiliate float of $33,407,943.90 (based on 4,841,731 shares held by non-affiliates as of March 10, 2026 at a price of $6.90 per share). The filing notes the last reported sales price was $6.50 on March 13, 2026.