# EDGAR Filing Document

**Accession Number:** 0001604464
**File Stem:** 0001193125-26-013362
**Filing Date:** 2026-1
**Character Count:** 21624
**Document Hash:** 00794b3ec437e43f6c821ed847417390
**Contains OCR:** False
**Source Format:** 

## Filing Content

## Filing Summary
**0001193125-26-013362.hdr.sgml**: 20260114

**ACCESSION NUMBER**: 0001193125-26-013362

**CONFORMED SUBMISSION TYPE**: SCHEDULE 13D/A

**PUBLIC DOCUMENT COUNT**: 1

**FILED AS OF DATE**: 20260114

**DATE AS OF CHANGE**: 20260114

**SUBJECT COMPANY**: 

**COMPANY DATA:**
- **COMPANY CONFORMED NAME:** Atara Biotherapeutics, Inc.
- **CENTRAL INDEX KEY:** 0001604464
- **STANDARD INDUSTRIAL CLASSIFICATION:** BIOLOGICAL PRODUCTS (NO DIAGNOSTIC SUBSTANCES) [2836]
- **ORGANIZATION NAME:** 03 Life Sciences
- **EIN:** 460920988
- **STATE OF INCORPORATION:** DE
- **FISCAL YEAR END:** 1231

**FILING VALUES:**
- **FORM TYPE:** SCHEDULE 13D/A
- **SEC ACT:** 1934 Act
- **SEC FILE NUMBER:** 005-88393
- **FILM NUMBER:** 26534569

**BUSINESS ADDRESS:**
- **STREET 1:** 1280 RANCHO CONEJO BLVD
- **CITY:** THOUSAND OAKS
- **STATE:** CA
- **ZIP:** 91320
- **BUSINESS PHONE:** 805-623-4211

**MAIL ADDRESS:**
- **STREET 1:** 1280 RANCHO CONEJO BLVD
- **CITY:** THOUSAND OAKS
- **STATE:** CA
- **ZIP:** 91320
**FILED BY**: 

**COMPANY DATA:**
- **COMPANY CONFORMED NAME:** Panacea Innovation Ltd
- **CENTRAL INDEX KEY:** 0002010692

**ORGANIZATION NAME:**
- **EIN:** 000000000
- **STATE OF INCORPORATION:** E9
- **FISCAL YEAR END:** 1231

**FILING VALUES:**
- **FORM TYPE:** SCHEDULE 13D/A

**BUSINESS ADDRESS:**
- **STREET 1:** C/O MAPLES CORPORATE SERVICES LIMITED
- **STREET 2:** BOX 309, UGLAND HOUSE
- **CITY:** GRAND CAYMAN
- **STATE:** E9
- **ZIP:** KY1-1104
- **BUSINESS PHONE:** 86 21 60252100

**MAIL ADDRESS:**
- **STREET 1:** C/O MAPLES CORPORATE SERVICES LIMITED
- **STREET 2:** BOX 309, UGLAND HOUSE
- **CITY:** GRAND CAYMAN
- **STATE:** E9
- **ZIP:** KY1-1104

### UNITED STATES SECURITIES AND EXCHANGE COMMISSION
**Washington, D.C. 20549**

## SCHEDULE 13D

### Under the Securities Exchange Act of 1934

**(Amendment No. 2)**

**Atara Biotherapeutics, Inc.**

*(Name of Issuer)*

**Common Stock**

*(Title of Class of Securities)*

**046513107**

*(CUSIP Number)*

**James Huang**<br>Panacea Venture<br>No. 5, Lane 1350, Fuxing Middle Road<br>Xuhui District, Shanghai F4 200031<br>(86-21) 6176-1101

*(Name, Address and Telephone Number of Person Authorized to Receive Notices and Communications)*

**01/12/2026**

*(Date of Event Which Requires Filing of this Statement)*

| **CUSIP No.** | **046513107** |

---

| | | | |
|:--|:--|:--|:--|
| 1 | Name of reporting person<br>**Panacea Innovation Limited** | Name of reporting person<br>**Panacea Innovation Limited** | |
| 2 | Check the appropriate box if a member of a Group (See Instructions)<br>[x] (a)<br>[ ] (b) | Check the appropriate box if a member of a Group (See Instructions)<br>[x] (a)<br>[ ] (b) | |
| 3 | SEC use only | SEC use only | |
| 4 | Source of funds (See Instructions)<br>**OO** | Source of funds (See Instructions)<br>**OO** | |
| 5 | Check if disclosure of legal proceedings is required pursuant to Items 2(d) or 2(e)<br>[ ] | Check if disclosure of legal proceedings is required pursuant to Items 2(d) or 2(e)<br>[ ] | |
| 6 | Citizenship or place of organization<br>**CAYMAN ISLANDS** | Citizenship or place of organization<br>**CAYMAN ISLANDS** | |
| Number of Shares<br>Beneficially Owned by<br>Each Reporting Person With: | 7 | Sole Voting Power<br>**0.00** |
| Number of Shares<br>Beneficially Owned by<br>Each Reporting Person With: | 8 | Shared Voting Power<br>**1632345.00** |
| Number of Shares<br>Beneficially Owned by<br>Each Reporting Person With: | 9 | Sole Dispositive Power<br>**0.00** |
| Number of Shares<br>Beneficially Owned by<br>Each Reporting Person With: | 10 | Shared Dispositive Power<br>**1632345.00** |
| 11 | Aggregate amount beneficially owned by each reporting person<br>**1632345.00** | Aggregate amount beneficially owned by each reporting person<br>**1632345.00** | |
| 12 | Check if the aggregate amount in Row (11) excludes certain shares (See Instructions)<br>[ ] | Check if the aggregate amount in Row (11) excludes certain shares (See Instructions)<br>[ ] | |
| 13 | Percent of class represented by amount in Row (11)<br>**19.99%** | Percent of class represented by amount in Row (11)<br>**19.99%** | |
| 14 | Type of Reporting Person (See Instructions)<br>**CO** | Type of Reporting Person (See Instructions)<br>**CO** | |

---

**Comment for Reporting Person:** Includes 259,163 warrants to purchase Common Stock. The warrants are immediately exercisable and do not expire. No portion of the warrants beneficially owned by the Reporting Persons may be exercised to the extent that, after giving effect to the attempted exercise, the Reporting Persons would beneficially own in excess of 19.99% of the outstanding Common Stock. Based on 7,258,971 shares of Common Stock outstanding as of November 28, 2025, the Reporting Persons may exercise warrants to purchase 97,345 shares of Common Stock.

| **CUSIP No.** | **046513107** |

---

| | | | |
|:--|:--|:--|:--|
| 1 | Name of reporting person<br>**Panacea Venture Healthcare Fund II, L.P.** | Name of reporting person<br>**Panacea Venture Healthcare Fund II, L.P.** | |
| 2 | Check the appropriate box if a member of a Group (See Instructions)<br>[x] (a)<br>[ ] (b) | Check the appropriate box if a member of a Group (See Instructions)<br>[x] (a)<br>[ ] (b) | |
| 3 | SEC use only | SEC use only | |
| 4 | Source of funds (See Instructions)<br>**OO** | Source of funds (See Instructions)<br>**OO** | |
| 5 | Check if disclosure of legal proceedings is required pursuant to Items 2(d) or 2(e)<br>[ ] | Check if disclosure of legal proceedings is required pursuant to Items 2(d) or 2(e)<br>[ ] | |
| 6 | Citizenship or place of organization<br>**CAYMAN ISLANDS** | Citizenship or place of organization<br>**CAYMAN ISLANDS** | |
| Number of Shares<br>Beneficially Owned by<br>Each Reporting Person With: | 7 | Sole Voting Power<br>**0.00** |
| Number of Shares<br>Beneficially Owned by<br>Each Reporting Person With: | 8 | Shared Voting Power<br>**1324446.00** |
| Number of Shares<br>Beneficially Owned by<br>Each Reporting Person With: | 9 | Sole Dispositive Power<br>**0.00** |
| Number of Shares<br>Beneficially Owned by<br>Each Reporting Person With: | 10 | Shared Dispositive Power<br>**1324446.00** |
| 11 | Aggregate amount beneficially owned by each reporting person<br>**1324446.00** | Aggregate amount beneficially owned by each reporting person<br>**1324446.00** | |
| 12 | Check if the aggregate amount in Row (11) excludes certain shares (See Instructions)<br>[ ] | Check if the aggregate amount in Row (11) excludes certain shares (See Instructions)<br>[ ] | |
| 13 | Percent of class represented by amount in Row (11)<br>**18.2%** | Percent of class represented by amount in Row (11)<br>**18.2%** | |
| 14 | Type of Reporting Person (See Instructions)<br>**PN** | Type of Reporting Person (See Instructions)<br>**PN** | |

---

| **CUSIP No.** | **046513107** |

---

| | | | |
|:--|:--|:--|:--|
| 1 | Name of reporting person<br>**Panacea Venture Healthcare Fund II GP Company, Ltd.** | Name of reporting person<br>**Panacea Venture Healthcare Fund II GP Company, Ltd.** | |
| 2 | Check the appropriate box if a member of a Group (See Instructions)<br>[x] (a)<br>[ ] (b) | Check the appropriate box if a member of a Group (See Instructions)<br>[x] (a)<br>[ ] (b) | |
| 3 | SEC use only | SEC use only | |
| 4 | Source of funds (See Instructions)<br>**OO** | Source of funds (See Instructions)<br>**OO** | |
| 5 | Check if disclosure of legal proceedings is required pursuant to Items 2(d) or 2(e)<br>[ ] | Check if disclosure of legal proceedings is required pursuant to Items 2(d) or 2(e)<br>[ ] | |
| 6 | Citizenship or place of organization<br>**CAYMAN ISLANDS** | Citizenship or place of organization<br>**CAYMAN ISLANDS** | |
| Number of Shares<br>Beneficially Owned by<br>Each Reporting Person With: | 7 | Sole Voting Power<br>**0.00** |
| Number of Shares<br>Beneficially Owned by<br>Each Reporting Person With: | 8 | Shared Voting Power<br>**1324446.00** |
| Number of Shares<br>Beneficially Owned by<br>Each Reporting Person With: | 9 | Sole Dispositive Power<br>**0.00** |
| Number of Shares<br>Beneficially Owned by<br>Each Reporting Person With: | 10 | Shared Dispositive Power<br>**1324446.00** |
| 11 | Aggregate amount beneficially owned by each reporting person<br>**1324446.00** | Aggregate amount beneficially owned by each reporting person<br>**1324446.00** | |
| 12 | Check if the aggregate amount in Row (11) excludes certain shares (See Instructions)<br>[ ] | Check if the aggregate amount in Row (11) excludes certain shares (See Instructions)<br>[ ] | |
| 13 | Percent of class represented by amount in Row (11)<br>**18.2%** | Percent of class represented by amount in Row (11)<br>**18.2%** | |
| 14 | Type of Reporting Person (See Instructions)<br>**CO** | Type of Reporting Person (See Instructions)<br>**CO** | |

---

| **CUSIP No.** | **046513107** |

---

| | | | |
|:--|:--|:--|:--|
| 1 | Name of reporting person<br>**Panacea Opportunity Fund I, L.P.** | Name of reporting person<br>**Panacea Opportunity Fund I, L.P.** | |
| 2 | Check the appropriate box if a member of a Group (See Instructions)<br>[x] (a)<br>[ ] (b) | Check the appropriate box if a member of a Group (See Instructions)<br>[x] (a)<br>[ ] (b) | |
| 3 | SEC use only | SEC use only | |
| 4 | Source of funds (See Instructions)<br>**OO** | Source of funds (See Instructions)<br>**OO** | |
| 5 | Check if disclosure of legal proceedings is required pursuant to Items 2(d) or 2(e)<br>[ ] | Check if disclosure of legal proceedings is required pursuant to Items 2(d) or 2(e)<br>[ ] | |
| 6 | Citizenship or place of organization<br>**CAYMAN ISLANDS** | Citizenship or place of organization<br>**CAYMAN ISLANDS** | |
| Number of Shares<br>Beneficially Owned by<br>Each Reporting Person With: | 7 | Sole Voting Power<br>**0.00** |
| Number of Shares<br>Beneficially Owned by<br>Each Reporting Person With: | 8 | Shared Voting Power<br>**307899.00** |
| Number of Shares<br>Beneficially Owned by<br>Each Reporting Person With: | 9 | Sole Dispositive Power<br>**0.00** |
| Number of Shares<br>Beneficially Owned by<br>Each Reporting Person With: | 10 | Shared Dispositive Power<br>**307899.00** |
| 11 | Aggregate amount beneficially owned by each reporting person<br>**307899.00** | Aggregate amount beneficially owned by each reporting person<br>**307899.00** | |
| 12 | Check if the aggregate amount in Row (11) excludes certain shares (See Instructions)<br>[ ] | Check if the aggregate amount in Row (11) excludes certain shares (See Instructions)<br>[ ] | |
| 13 | Percent of class represented by amount in Row (11)<br>**4.1%** | Percent of class represented by amount in Row (11)<br>**4.1%** | |
| 14 | Type of Reporting Person (See Instructions)<br>**PN** | Type of Reporting Person (See Instructions)<br>**PN** | |

---

**Comment for Reporting Person:** Includes 259,163  warrants to purchase Common Stock. The warrants are immediately exercisable and do not expire. No portion of the warrants beneficially owned by the Reporting Persons may be exercised to the extent that, after giving effect to the attempted exercise, the Reporting Persons would beneficially own in excess of 19.99% of the outstanding Common Stock. Based on 7,258,971 shares of Common Stock outstanding as of November 28, 2025, the Reporting Persons may exercise warrants to purchase 97,345 shares of Common Stock.

| **CUSIP No.** | **046513107** |

---

| | | | |
|:--|:--|:--|:--|
| 1 | Name of reporting person<br>**Panacea Opportunity Fund I GP Company, Ltd.** | Name of reporting person<br>**Panacea Opportunity Fund I GP Company, Ltd.** | |
| 2 | Check the appropriate box if a member of a Group (See Instructions)<br>[x] (a)<br>[ ] (b) | Check the appropriate box if a member of a Group (See Instructions)<br>[x] (a)<br>[ ] (b) | |
| 3 | SEC use only | SEC use only | |
| 4 | Source of funds (See Instructions)<br>**OO** | Source of funds (See Instructions)<br>**OO** | |
| 5 | Check if disclosure of legal proceedings is required pursuant to Items 2(d) or 2(e)<br>[ ] | Check if disclosure of legal proceedings is required pursuant to Items 2(d) or 2(e)<br>[ ] | |
| 6 | Citizenship or place of organization<br>**CAYMAN ISLANDS** | Citizenship or place of organization<br>**CAYMAN ISLANDS** | |
| Number of Shares<br>Beneficially Owned by<br>Each Reporting Person With: | 7 | Sole Voting Power<br>**0.00** |
| Number of Shares<br>Beneficially Owned by<br>Each Reporting Person With: | 8 | Shared Voting Power<br>**307899.00** |
| Number of Shares<br>Beneficially Owned by<br>Each Reporting Person With: | 9 | Sole Dispositive Power<br>**0.00** |
| Number of Shares<br>Beneficially Owned by<br>Each Reporting Person With: | 10 | Shared Dispositive Power<br>**307899.00** |
| 11 | Aggregate amount beneficially owned by each reporting person<br>**307899.00** | Aggregate amount beneficially owned by each reporting person<br>**307899.00** | |
| 12 | Check if the aggregate amount in Row (11) excludes certain shares (See Instructions)<br>[ ] | Check if the aggregate amount in Row (11) excludes certain shares (See Instructions)<br>[ ] | |
| 13 | Percent of class represented by amount in Row (11)<br>**4.1%** | Percent of class represented by amount in Row (11)<br>**4.1%** | |
| 14 | Type of Reporting Person (See Instructions)<br>**CO** | Type of Reporting Person (See Instructions)<br>**CO** | |

---

**Comment for Reporting Person:** Includes 259,163  warrants to purchase Common Stock. The warrants are immediately exercisable and do not expire. No portion of the warrants beneficially owned by the Reporting Persons may be exercised to the extent that, after giving effect to the attempted exercise, the Reporting Persons would beneficially own in excess of 19.99% of the outstanding Common Stock. Based on 7,258,971 shares of Common Stock outstanding as of November 28, 2025, the Reporting Persons may exercise warrants to purchase 97,345 shares of Common Stock.

| **CUSIP No.** | **046513107** |

---

| | | | |
|:--|:--|:--|:--|
| 1 | Name of reporting person<br>**James Huang** | Name of reporting person<br>**James Huang** | |
| 2 | Check the appropriate box if a member of a Group (See Instructions)<br>[x] (a)<br>[ ] (b) | Check the appropriate box if a member of a Group (See Instructions)<br>[x] (a)<br>[ ] (b) | |
| 3 | SEC use only | SEC use only | |
| 4 | Source of funds (See Instructions)<br>**OO** | Source of funds (See Instructions)<br>**OO** | |
| 5 | Check if disclosure of legal proceedings is required pursuant to Items 2(d) or 2(e)<br>[ ] | Check if disclosure of legal proceedings is required pursuant to Items 2(d) or 2(e)<br>[ ] | |
| 6 | Citizenship or place of organization<br>**CHINA** | Citizenship or place of organization<br>**CHINA** | |
| Number of Shares<br>Beneficially Owned by<br>Each Reporting Person With: | 7 | Sole Voting Power<br>**0.00** |
| Number of Shares<br>Beneficially Owned by<br>Each Reporting Person With: | 8 | Shared Voting Power<br>**1632345.00** |
| Number of Shares<br>Beneficially Owned by<br>Each Reporting Person With: | 9 | Sole Dispositive Power<br>**0.00** |
| Number of Shares<br>Beneficially Owned by<br>Each Reporting Person With: | 10 | Shared Dispositive Power<br>**1632345.00** |
| 11 | Aggregate amount beneficially owned by each reporting person<br>**1632345.00** | Aggregate amount beneficially owned by each reporting person<br>**1632345.00** | |
| 12 | Check if the aggregate amount in Row (11) excludes certain shares (See Instructions)<br>[ ] | Check if the aggregate amount in Row (11) excludes certain shares (See Instructions)<br>[ ] | |
| 13 | Percent of class represented by amount in Row (11)<br>**19.99%** | Percent of class represented by amount in Row (11)<br>**19.99%** | |
| 14 | Type of Reporting Person (See Instructions)<br>**IN** | Type of Reporting Person (See Instructions)<br>**IN** | |

---

**Comment for Reporting Person:** Includes 259,163  warrants to purchase Common Stock. The warrants are immediately exercisable and do not expire. No portion of the warrants beneficially owned by the Reporting Persons may be exercised to the extent that, after giving effect to the attempted exercise, the Reporting Persons would beneficially own in excess of 19.99% of the outstanding Common Stock. Based on 7,258,971 shares of Common Stock outstanding as of November 28, 2025, the Reporting Persons may exercise warrants to purchase 97,345 shares of Common Stock.

**Item 1. Security and Issuer**

**(a) Title of Class of Securities:**
Common Stock

**(b) Name of Issuer:**
Atara Biotherapeutics, Inc.

**(c) Address of Issuer's Principal Executive Offices:**
1280 Rancho Conejo Blvd, Thousand Oaks, CA, 91320

This Amendment No. 2 to Schedule 13D amends and supplements the statement on Schedule 13D originally filed with the United States Securities and Exchange Commission on May 21, 2025 (as amended, the "Schedule 13D"), relating to the Common Stock. Capitalized terms used herein without definition shall have the meaning set forth in the Schedule 13D.

**Item 5. Interest in Securities of the Issuer**

**(a)**
The information contained on the cover pages is incorporated by reference into this Item 5.

Panacea Venture Healthcare Fund II, L.P. is the record holder of 1,324,446 shares of Common Stock, and Panacea Opportunity Fund I, L.P. is the record holder of 48,736 shares of Common Stock and warrants to purchase 259,163 shares of Common Stock. The warrants are immediately exercisable and do not expire. No portion of the warrants beneficially owned by the Reporting Persons may be exercised to the extent that, after giving effect to the attempted exercise, the Reporting Persons would beneficially own in excess of 19.99% of the outstanding Common Stock.

James Huang is the sole owner of Panacea Innovation Limited, which is the sole owner of Panacea Venture Healthcare Fund II GP Company, Ltd. and Panacea Opportunity Fund I GP Company, Ltd., which are the general partners of Panacea Venture Healthcare Fund II, L.P. and Panacea Opportunity Fund I, L.P., respectively. As a result, Panacea Venture Healthcare Fund II GP Company, Ltd. and Panacea Opportunity Fund I GP Company, Ltd. may be deemed to share beneficial ownership of the securities held of record by Panacea Venture Healthcare Fund II, L.P. and Panacea Opportunity Fund I, L.P., respectively. Panacea Innovation Limited and Mr. Huang may be deemed to share beneficial ownership of the securities beneficially owned by the foregoing entities, but each disclaims such beneficial ownership.

**(b)**
The information contained on the cover pages is incorporated by reference into this Item 5.

**(c)**
On November 28, 2025, Panacea Opportunity Fund I, L.P. exercised warrants to purchase an aggregate of 48,736 shares of Common Stock, after tax witholding. On January 12, 2026, Panacea Venture Healthcare Fund II, L.P.  sold 80,554 shares of Common Stock in open market transactions at a weighted average price of $6.0707 per share.  The Reporting Persons undertake to provide, upon request by the staff of the Securities and Exchange Commission, the Issuer, or a security holder of the Issuer, full information regarding the number of shares sold at each separate price for this transaction.

### SIGNATURE

After reasonable inquiry and to the best of my knowledge and belief, I certify that the information set forth in this statement is true, complete and correct.

**Reporting Person:** Panacea Innovation Limited

**Signature:** /s/ James Huang

**Name/Title:** James Huang, Founding Managing Partner

**Date:** 01/14/2026

After reasonable inquiry and to the best of my knowledge and belief, I certify that the information set forth in this statement is true, complete and correct.

**Reporting Person:** Panacea Venture Healthcare Fund II, L.P.

**Signature:** By: Panacea Venture Healthcare Fund II GP Company, Ltd., its general partner By: Panacea Innovation Limited, its sole owner By: /s/ James Huang

**Name/Title:** James Huang, Founding Managing Partner

**Date:** 01/14/2026

After reasonable inquiry and to the best of my knowledge and belief, I certify that the information set forth in this statement is true, complete and correct.

**Reporting Person:** Panacea Venture Healthcare Fund II GP Company, Ltd.

**Signature:** By: Panacea Innovation Limited, its sole owner By: /s/ James Huang

**Name/Title:** James Huang, Founding Managing Partner

**Date:** 01/14/2026

After reasonable inquiry and to the best of my knowledge and belief, I certify that the information set forth in this statement is true, complete and correct.

**Reporting Person:** Panacea Opportunity Fund I, L.P.

**Signature:** By: Panacea Opportunity Fund I GP Company, Ltd., its general partner By: Panacea Innovation Limited, its sole owner By: /s/ James Huang

**Name/Title:** James Huang, Founding Managing Partner

**Date:** 01/14/2026

After reasonable inquiry and to the best of my knowledge and belief, I certify that the information set forth in this statement is true, complete and correct.

**Reporting Person:** Panacea Opportunity Fund I GP Company, Ltd.

**Signature:** By: Panacea Innovation Limited, its sole owner By: /s/ James Huang

**Name/Title:** James Huang, Founding Managing Partner

**Date:** 01/14/2026

After reasonable inquiry and to the best of my knowledge and belief, I certify that the information set forth in this statement is true, complete and correct.

**Reporting Person:** James Huang

**Signature:** /s/ James Huang

**Name/Title:** James Huang

**Date:** 01/14/2026