|
SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549 |
SCHEDULE 13G
|
UNDER THE SECURITIES EXCHANGE ACT OF 1934
|
Boundless Bio, Inc. (Name of Issuer) |
Common stock, par value $0.0001 per share (the "Shares") (Title of Class of Securities) |
10170A100 (CUSIP Number) |
11/26/2025 (Date of Event Which Requires Filing of this Statement) |
| Check the appropriate box to designate the rule pursuant to which this Schedule is filed: |
 Rule 13d-1(b)
|
 Rule 13d-1(c)
|
| Rule 13d-1(d)
|
SCHEDULE 13G
|
| CUSIP No. | 10170A100 |
| 1 | Names of Reporting Persons
Citadel Advisors LLC | ||||||||
| 2 | Check the appropriate box if a member of a Group (see instructions)
(a)
(b)
| ||||||||
| 3 | Sec Use Only | ||||||||
| 4 | Citizenship or Place of Organization
DELAWARE
| ||||||||
| Number of Shares Beneficially Owned by Each Reporting Person With: |
| ||||||||
| 9 | Aggregate Amount Beneficially Owned by Each Reporting Person
830,936.00 | ||||||||
| 10 | Check box if the aggregate amount in row (9) excludes certain shares (See Instructions)
| ||||||||
| 11 | Percent of class represented by amount in row (9)
3.7 % | ||||||||
| 12 | Type of Reporting Person (See Instructions)
IA, HC, OO |
Comment for Type of Reporting Person: The percentages reported in this Schedule 13G are based upon 22,385,611 Shares outstanding as of October 31, 2025 (according to the issuer's Form 10-Q as filed with the Securities and Exchange Commission on November 5, 2025). Except as described in the preceding sentence, all Shares for the holdings of the reporting persons reported in this Schedule 13G are as of the opening of the market on December 4, 2025.
SCHEDULE 13G
|
| CUSIP No. | 10170A100 |
| 1 | Names of Reporting Persons
Citadel Advisors Holdings LP | ||||||||
| 2 | Check the appropriate box if a member of a Group (see instructions)
(a)
(b)
| ||||||||
| 3 | Sec Use Only | ||||||||
| 4 | Citizenship or Place of Organization
DELAWARE
| ||||||||
| Number of Shares Beneficially Owned by Each Reporting Person With: |
| ||||||||
| 9 | Aggregate Amount Beneficially Owned by Each Reporting Person
830,936.00 | ||||||||
| 10 | Check box if the aggregate amount in row (9) excludes certain shares (See Instructions)
| ||||||||
| 11 | Percent of class represented by amount in row (9)
3.7 % | ||||||||
| 12 | Type of Reporting Person (See Instructions)
HC, PN |
SCHEDULE 13G
|
| CUSIP No. | 10170A100 |
| 1 | Names of Reporting Persons
Citadel GP LLC | ||||||||
| 2 | Check the appropriate box if a member of a Group (see instructions)
(a)
(b)
| ||||||||
| 3 | Sec Use Only | ||||||||
| 4 | Citizenship or Place of Organization
DELAWARE
| ||||||||
| Number of Shares Beneficially Owned by Each Reporting Person With: |
| ||||||||
| 9 | Aggregate Amount Beneficially Owned by Each Reporting Person
830,936.00 | ||||||||
| 10 | Check box if the aggregate amount in row (9) excludes certain shares (See Instructions)
| ||||||||
| 11 | Percent of class represented by amount in row (9)
3.7 % | ||||||||
| 12 | Type of Reporting Person (See Instructions)
HC, OO |
SCHEDULE 13G
|
| CUSIP No. | 10170A100 |
| 1 | Names of Reporting Persons
Citadel Securities LLC | ||||||||
| 2 | Check the appropriate box if a member of a Group (see instructions)
(a)
(b)
| ||||||||
| 3 | Sec Use Only | ||||||||
| 4 | Citizenship or Place of Organization
DELAWARE
| ||||||||
| Number of Shares Beneficially Owned by Each Reporting Person With: |
| ||||||||
| 9 | Aggregate Amount Beneficially Owned by Each Reporting Person
602,452.00 | ||||||||
| 10 | Check box if the aggregate amount in row (9) excludes certain shares (See Instructions)
| ||||||||
| 11 | Percent of class represented by amount in row (9)
2.7 % | ||||||||
| 12 | Type of Reporting Person (See Instructions)
BD, OO |
SCHEDULE 13G
|
| CUSIP No. | 10170A100 |
| 1 | Names of Reporting Persons
Citadel Securities Group LP | ||||||||
| 2 | Check the appropriate box if a member of a Group (see instructions)
(a)
(b)
| ||||||||
| 3 | Sec Use Only | ||||||||
| 4 | Citizenship or Place of Organization
DELAWARE
| ||||||||
| Number of Shares Beneficially Owned by Each Reporting Person With: |
| ||||||||
| 9 | Aggregate Amount Beneficially Owned by Each Reporting Person
602,452.00 | ||||||||
| 10 | Check box if the aggregate amount in row (9) excludes certain shares (See Instructions)
| ||||||||
| 11 | Percent of class represented by amount in row (9)
2.7 % | ||||||||
| 12 | Type of Reporting Person (See Instructions)
HC, PN |
SCHEDULE 13G
|
| CUSIP No. | 10170A100 |
| 1 | Names of Reporting Persons
Citadel Securities GP LLC | ||||||||
| 2 | Check the appropriate box if a member of a Group (see instructions)
(a)
(b)
| ||||||||
| 3 | Sec Use Only | ||||||||
| 4 | Citizenship or Place of Organization
DELAWARE
| ||||||||
| Number of Shares Beneficially Owned by Each Reporting Person With: |
| ||||||||
| 9 | Aggregate Amount Beneficially Owned by Each Reporting Person
602,452.00 | ||||||||
| 10 | Check box if the aggregate amount in row (9) excludes certain shares (See Instructions)
| ||||||||
| 11 | Percent of class represented by amount in row (9)
2.7 % | ||||||||
| 12 | Type of Reporting Person (See Instructions)
HC, OO |
SCHEDULE 13G
|
| CUSIP No. | 10170A100 |
| 1 | Names of Reporting Persons
Kenneth Griffin | ||||||||
| 2 | Check the appropriate box if a member of a Group (see instructions)
(a)
(b)
| ||||||||
| 3 | Sec Use Only | ||||||||
| 4 | Citizenship or Place of Organization
UNITED STATES
| ||||||||
| Number of Shares Beneficially Owned by Each Reporting Person With: |
| ||||||||
| 9 | Aggregate Amount Beneficially Owned by Each Reporting Person
1,433,388.00 | ||||||||
| 10 | Check box if the aggregate amount in row (9) excludes certain shares (See Instructions)
| ||||||||
| 11 | Percent of class represented by amount in row (9)
6.4 % | ||||||||
| 12 | Type of Reporting Person (See Instructions)
HC, IN |
SCHEDULE 13G
|
| Item 1. | ||
| (a) | Name of issuer:
Boundless Bio, Inc. | |
| (b) | Address of issuer's principal executive offices:
10955 Alexandria Way, Suite 100 San Diego, CA, 92121 | |
| Item 2. | ||
| (a) | Name of person filing:
This Schedule 13G is being jointly filed by Citadel Advisors LLC ("Citadel Advisors"), Citadel Advisors Holdings LP ("CAH"), Citadel GP LLC ("CGP"), Citadel Securities LLC ("Citadel Securities"), Citadel Securities Group LP ("CALC4"), Citadel Securities GP LLC ("CSGP") and Mr. Kenneth Griffin (collectively with Citadel Advisors, CAH, CGP, Citadel Securities, CALC4 and CSGP, the "Reporting Persons") with respect to the Shares of the above-named issuer owned by Citadel Multi-Strategy Equities Master Fund Ltd., a Cayman Islands company ("CM"), and Citadel Securities. Such owned Shares may include other instruments exercisable for or convertible into Shares.
Citadel Advisors is the portfolio manager for CM. CAH is the sole member of Citadel Advisors. CGP is the general partner of CAH. CALC4 is the non-member manager of Citadel Securities. CSGP is the general partner of CALC4. Mr. Griffin is the President and Chief Executive Officer of CGP, and owns a controlling interest in CGP and CSGP.
The filing of this statement shall not be construed as an admission that any of the Reporting Persons is the beneficial owner of any securities covered by the statement other than the securities actually owned by such person (if any). | |
| (b) | Address or principal business office or, if none, residence:
The address of each of the Reporting Persons is 830 Brickell Plaza, Miami, Florida 33131. | |
| (c) | Citizenship:
Each of Citadel Advisors, CGP, Citadel Securities and CSGP is organized as a limited liability company under the laws of the State of Delaware. Each of CALC4 and CAH is organized as a limited partnership under the laws of the State of Delaware. Mr. Griffin is a U.S. citizen. | |
| (d) | Title of class of securities:
Common stock, par value $0.0001 per share (the "Shares") | |
| (e) | CUSIP No.:
10170A100 | |
| Item 3. | If this statement is filed pursuant to §§ 240.13d-1(b) or 240.13d-2(b) or (c), check whether the person filing is a: | |
| (a) | Broker or dealer registered under section 15 of the Act (15 U.S.C. 78o);
| |
| (b) | Bank as defined in section 3(a)(6) of the Act (15 U.S.C. 78c);
| |
| (c) | Insurance company as defined in section 3(a)(19) of the Act (15 U.S.C. 78c);
| |
| (d) | Investment company registered under section 8 of the Investment Company Act of 1940 (15 U.S.C. 80a-8);
| |
| (e) | An investment adviser in accordance with § 240.13d-1(b)(1)(ii)(E);
| |
| (f) | An employee benefit plan or endowment fund in accordance with § 240.13d-1(b)(1)(ii)(F);
| |
| (g) | A parent holding company or control person in accordance with § 240.13d-1(b)(1)(ii)(G);
| |
| (h) | A savings associations as defined in Section 3(b) of the Federal Deposit Insurance Act (12 U.S.C. 1813);
| |
| (i) | A church plan that is excluded from the definition of an investment company under section 3(c)(14) of the Investment Company Act of 1940 (15 U.S.C. 80a-3);
| |
| (j) | A non-U.S. institution in accordance with § 240.13d-1(b)(1)(ii)(J). If filing as a non-U.S. institution in accordance with § 240.13d-1(b)(1)(ii)(J),
please specify the type of institution: | |
| (k) | Group, in accordance with Rule 240.13d-1(b)(1)(ii)(K).
| |
| Item 4. | Ownership | |
| (a) | Amount beneficially owned:
1. Each of Citadel Advisors LLC, Citadel Advisors Holdings LP and Citadel GP LLC may be deemed to beneficially own 830,936 Shares.
2. Citadel Securities LLC may be deemed to beneficially own 602,452 Shares.
3. Each of Citadel Securities Group LP and Citadel Securities GP LLC may be deemed to beneficially own 602,452 Shares.
4. Mr. Griffin may be deemed to beneficially own 1,433,388 Shares. | |
| (b) | Percent of class:
1. The number of Shares that each of Citadel Advisors LLC, Citadel Advisors Holdings LP and Citadel GP LLC may be deemed to beneficially own constitutes 3.7% of the Shares outstanding.
2. The number of Shares that Citadel Securities LLC may be deemed to beneficially own constitutes 2.7% of the Shares outstanding.
3. The number of Shares that each of Citadel Securities Group LP and Citadel Securities GP LLC may be deemed to beneficially own constitutes 2.7% of the Shares outstanding.
4. The number of Shares that Mr. Griffin may be deemed to beneficially own constitutes 6.4% of the Shares outstanding. %
| |
| (c) | Number of shares as to which the person has:
| |
| (i) Sole power to vote or to direct the vote:
1. Each of Citadel Advisors LLC, Citadel Advisors Holdings LP and Citadel GP LLC: 0
2. Citadel Securities LLC: 0
3. Each of Citadel Securities Group LP and Citadel Securities GP LLC: 0
4. Mr. Griffin: 0 | ||
| (ii) Shared power to vote or to direct the vote:
1. Each of Citadel Advisors LLC, Citadel Advisors Holdings LP and Citadel GP LLC: 830,936
2. Citadel Securities LLC: 602,452
3. Each of Citadel Securities Group LP and Citadel Securities GP LLC: 602,452
4. Mr. Griffin: 1,433,388 | ||
| (iii) Sole power to dispose or to direct the disposition of:
1. Each of Citadel Advisors LLC, Citadel Advisors Holdings LP and Citadel GP LLC: 0
2. Citadel Securities LLC: 0
3. Each of Citadel Securities Group LP and Citadel Securities GP LLC: 0
4. Mr. Griffin: 0 | ||
| (iv) Shared power to dispose or to direct the disposition of:
1. Each of Citadel Advisors LLC, Citadel Advisors Holdings LP and Citadel GP LLC: 830,936
2. Citadel Securities LLC: 602,452
3. Each of Citadel Securities Group LP and Citadel Securities GP LLC: 602,452
4. Mr. Griffin: 1,433,388 | ||
| Item 5. | Ownership of 5 Percent or Less of a Class. | |
| Item 6. | Ownership of more than 5 Percent on Behalf of Another Person. | |
Not Applicable
| ||
| Item 7. | Identification and Classification of the Subsidiary Which Acquired the Security Being Reported on by the Parent Holding Company or Control Person. | |
Not Applicable
| ||
| Item 8. | Identification and Classification of Members of the Group. | |
Not Applicable
| ||
| Item 9. | Notice of Dissolution of Group. | |
Not Applicable
| ||
| Item 10. | Certifications: |
By signing below I certify that, to the best of my knowledge and belief, the securities referred to above were not acquired and are not held for the purpose of or with the effect of changing or influencing the control of the issuer of the securities and were not acquired and are not held in connection with or as a participant in any transaction having that purpose or effect, other than activities solely in connection with a nomination under ?? 240.14a-11. |
| 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.
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
Comments accompanying signature: * Seth Levy is signing on behalf of Kenneth Griffin as attorney-in-fact pursuant to a power of attorney previously filed with the Securities and Exchange Commission, and hereby incorporated by reference herein. The power of attorney was filed as an attachment to a filing by Citadel Advisors LLC on Schedule 13G for Allakos Inc. on October 13, 2023.
Exhibit Information
|
Exhibit 99.1 - Joint Filing Agreement |
EXHIBIT 99.1
JOINT FILING AGREEMENT
The undersigned hereby agree that the Statement on Schedule 13G filed herewith (and any amendments thereto), relating to the Shares, is being filed jointly with the Securities and Exchange Commission pursuant to Rule 13d-1(c) under the Securities Exchange Act of 1934, as amended, on behalf of each of the undersigned.
This Agreement may be executed in counterparts and each of such counterparts taken together shall constitute one and the same instrument.
Dated December 4, 2025.
| CITADEL SECURITIES LLC | CITADEL ADVISORS LLC | |||
| By: | /s/ Seth Levy | By: | /s/ Seth Levy | |
| Seth Levy, Authorized Signatory | Seth Levy, Authorized Signatory | |||
| CITADEL SECURITIES GROUP LP | CITADEL ADVISORS HOLDINGS LP | |||
| By: | /s/ Seth Levy | By: | /s/ Seth Levy | |
| Seth Levy, Authorized Signatory | Seth Levy, Authorized Signatory | |||
| CITADEL SECURITIES GP LLC | CITADEL GP LLC | |||
| By: | /s/ Seth Levy | By: | /s/ Seth Levy | |
| Seth Levy, Authorized Signatory | Seth Levy, Authorized Signatory | |||
| KENNETH GRIFFIN | ||||
| By: | /s/ Seth Levy | |||
| Seth Levy, attorney-in-fact* | ||||
| * | Seth Levy is signing on behalf of Kenneth Griffin as attorney-in-fact pursuant to a power of attorney previously filed with the Securities and Exchange Commission, and hereby incorporated by reference herein. The power of attorney was filed as an attachment to a filing by Citadel Advisors LLC on Schedule 13G for Allakos Inc. on October 13, 2023. |