13D Filings
Atara Biotherapeutics, Inc.
ATRA
Amendment
Ownership

19.99%

Total Shares

1,370,081

Issuer CIK

1604464

CUSIP

046513107

Event Date

May 13, 2025

Accepted

May 16, 2025, 06:28 PM

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
Adiumentum Capital Fund I LP
Investment Adviser
19.99%1,370,08101,370,081
Adiumentum Capital Fund I GP LLC
Investment Adviser
19.99%1,370,08101,370,081
Gregory A. Ciongoli
Investment Adviser
19.99%1,370,08101,370,081
Disclosure Items (6)

Security Title

Common Stock, par value $0.0001 per share

Issuer Name

Atara Biotherapeutics, Inc.

Issuer Address

1280 Rancho Conejo Blvd, Thousand Oaks, CA, 91320

Item 3 of the Initial 13D is hereby amended and restated in its entirety as follows: The Responses to Item 4, 5 and 6 of this Schedule 13D are incorporated herein by reference. The investment costs (including commissions, if any) of the Common Stock and the Pre-Funded Warrants directly owned by Adiumentum is approximately $1,999,978.22. The source of funding for such transactions was derived from the capital of Adiumentum.

Item 4 of the Initial 13D is hereby amended and supplemented to add the following information: On May 14, 2025, Adiumentum agreed to purchase from the Issuer in connection with a registered offering (the "Registered Offering") an aggregate of (i) 75,572 shares (the "Shares") of the Issuer's common stock, par value $0.0001 per share (the "Common Stock"), and (ii) pre-funded warrants (each, a "Pre-Funded Warrant", and together, the "Pre-Funded Warrants") to purchase up to 227,000 shares of Common Stock, at a purchase price of $6.61 per share of Common Stock and $6.6099 per share of Common Stock issuable upon exercise of the Pre-Funded Warrants. The exercise price of each Pre-Funded Warrant is equal to $0.0001 per share, subject to adjustment as provided therein, and the Pre-Funded Warrants will be exercisable immediately and have no expiration date. The Pre-Funded Warrants may be exercised by means of cash or the holder may elect to receive upon such exercise the net number of shares of Common Stock determined according to a formula set forth in the Pre-Funded Warrants. The Registered Offering closed on May 16, 2025. The foregoing is only a summary of the terms of the Pre-Funded Warrants issued to Adiumentum in connection with the Registered Offering, and does not purport to be complete and is qualified in its entirety by reference to the full text of the form of Pre-Funded Warrant, a copy of which is filed as Exhibit 99.3 hereto.

Percentage of Class

Items 5(a) and (b) of the Initial 13D are hereby amended and restated in their entirety to read as follows: The Reporting Persons each beneficially owns an aggregate of 1,370,081 shares of Common Stock (the "Subject Shares"). The Subject Shares represent approximately 19.99% of the outstanding shares of Common Stock, based on 6,639,146 shares of Common Stock outstanding as of May 16, 2025, as reported in the Issuer's prospectus supplement filed with the SEC on May 16, 2025, giving effect to the Registered Offering in which 75,572 shares of Common Stock and 227,000 Pre-Funded Warrants were issued to Adiumentum Capital Fund I LP. Adiumentum may be deemed to have the shared power to vote or direct the vote of (and the shared power to dispose or direct the disposition of) all of the Subject Shares. Adiumentum GP, as the general partner of Adiumentum may be deemed to have the shared power to vote or direct the vote of (and the shared power to dispose or direct the disposition of) all the Subject Shares. Mr. Ciongoli, as the managing partner of Adiumentum, and as the managing member of Adiumentum GP, may be deemed to have the shared power to vote or direct the vote of (and the shared power to dispose or direct the disposition of) all the Subject Shares.

Number of Shares

See response to Item 5(a) above.

Transactions

Other than as disclosed in Item 4 of this Amendment No.2, no reportable transactions were effected by any Reporting Person during the past sixty days.

Item 6 of the Initial 13D is hereby amended and supplemented to add the information contained in Item 4 to this Amendment No. 2, which information is incorporated herein by reference.

Exhibit 99.3 Form of Pre-Funded Warrant (incorporated by reference to Exhibit 4.1 to the Current Report on Form 8-K filed by the Issuer with the SEC on May 16, 2024).

Atara Biotherapeutics, Inc. — Schedule 13D | 13D Filings