Atara Biotherapeutics, Inc. filed a Form S-3 registration statement with the SEC on November 10, 2026, replacing an expiring shelf registration and covering up to $200,000,000 in securities plus up to $23,011,805 in common stock available through an at-the-market equity offering program with TD Cowen.

Key Highlights

  • Replacement shelf: The filing replaces the prior Form S-3 (File No. 333-275256), declared effective November 13, 2023, which is due to expire on November 13, 2026.
  • Base prospectus amount: Up to $200,000,000 in aggregate of common stock, preferred stock, debt securities, warrants, rights, and units may be offered over time.
  • ATM program limit: Up to $23,011,805 of common stock may be offered and sold through TD Cowen under the existing Sales Agreement dated November 1, 2023, as disclosed in the sales agreement prospectus.
  • Public float constraint: The company disclosed a public float of approximately $69,035,417, based on 6,828,429 shares held by non-affiliates at a closing price of $10.11 per share, limiting primary offering sales to no more than one-third of that float in any 12-month period under General Instruction I.B.6 of Form S-3.
  • Filer status: Atara Biotherapeutics is classified as a non-accelerated filer and a smaller reporting company, and is not an emerging growth company.
  • Sales agent succession: TD Securities (USA) LLC, operating as TD Cowen, is now the sales agent under the Sales Agreement as successor to Cowen and Company, LLC.

Atara Biotherapeutics Renews Shelf Registration as Prior Statement Nears Expiry

According to the filing, Atara Biotherapeutics, Inc. (NASDAQ:ATRA) submitted this Form S-3 registration statement on November 10, 2026, as a replacement registration pursuant to Rule 415(a)(6) under the Securities Act of 1933. The company disclosed that its prior shelf registration (File No. 333-275256), filed November 1, 2023, and effective November 13, 2023, is set to expire on November 13, 2026, prompting the need for a replacement to maintain the ability to access public capital markets on a continuous or delayed basis.

The registration statement contains two components, as described in the filing. The first is a base prospectus covering potential offerings of up to $200,000,000 in aggregate across multiple security types, including common stock, preferred stock, debt securities, warrants, rights, and units. The second is a sales agreement prospectus specifically covering up to $23,011,805 of common stock to be sold from time to time through TD Cowen under an at-the-market program. The filing states that the $23,011,805 ATM amount is included within, and not in addition to, the $200,000,000 base prospectus total.

The company noted that because its public float remains below $75,000,000, it is subject to the limitation in General Instruction I.B.6 of Form S-3, which restricts public primary offering sales to no more than one-third of the public float held by non-affiliates in any 12-month period. The filing disclosed that the amount the company may sell under this constraint, as of the filing date, is $23,011,805. The registration statement also states that, pursuant to Rule 415(a)(6), the offering of unsold securities under the prior registration statement will be deemed terminated upon the effectiveness of this new registration statement.

What Was Disclosed

Atara Biotherapeutics filed a replacement S-3 shelf registration on November 10, 2026, covering up to $200,000,000 in securities and up to $23,011,805 in common stock through an at-the-market program with TD Cowen, replacing a shelf set to expire November 13, 2026.