Form SCHEDULE 13G/A Boundless Bio, Inc. Filed by: CITADEL ADVISORS LLC
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SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549 |
SCHEDULE 13G
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UNDER THE SECURITIES EXCHANGE ACT OF 1934
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(Amendment No. 1)*
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Boundless Bio, Inc. (Name of Issuer) |
Common stock, par value $0.0001 per share (the "Shares") (Title of Class of Securities) |
(CUSIP Number) |
06/30/2026 (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
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| CUSIP No. |
| 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
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| Number of Shares Beneficially Owned by Each Reporting Person With: |
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| 9 | Aggregate Amount Beneficially Owned by Each Reporting Person
0.00 | ||||||||
| 10 | Check box if the aggregate amount in row (9) excludes certain shares (See Instructions)
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| 11 | Percent of class represented by amount in row (9)
0.0 % | ||||||||
| 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 22,474,777 Shares outstanding as of June 15, 2026 (according to the issuer's prospectus as filed with the Securities and Exchange Commission on June 23, 2026).
SCHEDULE 13G
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| CUSIP No. |
| 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
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| Number of Shares Beneficially Owned by Each Reporting Person With: |
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| 9 | Aggregate Amount Beneficially Owned by Each Reporting Person
0.00 | ||||||||
| 10 | Check box if the aggregate amount in row (9) excludes certain shares (See Instructions)
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| 11 | Percent of class represented by amount in row (9)
0.0 % | ||||||||
| 12 | Type of Reporting Person (See Instructions)
HC, PN |
SCHEDULE 13G
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| CUSIP No. |
| 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
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| Number of Shares Beneficially Owned by Each Reporting Person With: |
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| 9 | Aggregate Amount Beneficially Owned by Each Reporting Person
0.00 | ||||||||
| 10 | Check box if the aggregate amount in row (9) excludes certain shares (See Instructions)
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| 11 | Percent of class represented by amount in row (9)
0.0 % | ||||||||
| 12 | Type of Reporting Person (See Instructions)
HC, OO |
SCHEDULE 13G
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| CUSIP No. |
| 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
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| Number of Shares Beneficially Owned by Each Reporting Person With: |
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| 9 | Aggregate Amount Beneficially Owned by Each Reporting Person
65,617.00 | ||||||||
| 10 | Check box if the aggregate amount in row (9) excludes certain shares (See Instructions)
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| 11 | Percent of class represented by amount in row (9)
0.3 % | ||||||||
| 12 | Type of Reporting Person (See Instructions)
BD, OO |
SCHEDULE 13G
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| CUSIP No. |
| 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
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| Number of Shares Beneficially Owned by Each Reporting Person With: |
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| 9 | Aggregate Amount Beneficially Owned by Each Reporting Person
145,118.00 | ||||||||
| 10 | Check box if the aggregate amount in row (9) excludes certain shares (See Instructions)
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| 11 | Percent of class represented by amount in row (9)
0.6 % | ||||||||
| 12 | Type of Reporting Person (See Instructions)
HC, PN |
SCHEDULE 13G
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| CUSIP No. |
| 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
145,118.00 | ||||||||
| 10 | Check box if the aggregate amount in row (9) excludes certain shares (See Instructions)
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| 11 | Percent of class represented by amount in row (9)
0.6 % | ||||||||
| 12 | Type of Reporting Person (See Instructions)
HC, OO |
SCHEDULE 13G
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| CUSIP No. |
| 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
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| Number of Shares Beneficially Owned by Each Reporting Person With: |
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| 9 | Aggregate Amount Beneficially Owned by Each Reporting Person
145,118.00 | ||||||||
| 10 | Check box if the aggregate amount in row (9) excludes certain shares (See Instructions)
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| 11 | Percent of class represented by amount in row (9)
0.6 % | ||||||||
| 12 | Type of Reporting Person (See Instructions)
HC, IN |
SCHEDULE 13G
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| Item 1. | ||
| (a) | Name of issuer:
Boundless Bio, Inc. | |
| (b) | Address of issuer's principal executive offices:
11099 North Torrey Pines Road, Suite 150, La Jolla, CA, 92037 | |
| 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 held of record by Citadel Securities and CRBU Holdings LLC, a Delaware limited liability company ("CRBH"). Such Shares may include other instruments exercisable for or convertible into Shares.
CAH is the sole member of Citadel Advisors. CGP is the general partner of CAH. CALC4 is the non-member manager of Citadel Securities and CRBH. 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. | |
| (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.:
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| 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 0 Shares.
2. Citadel Securities LLC may be deemed to beneficially own 65,617 Shares.
3. Each of Citadel Securities Group LP and Citadel Securities GP LLC may be deemed to beneficially own 145,118 Shares.
4. Mr. Griffin may be deemed to beneficially own 145,118 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 0.0% of the Shares outstanding.
2. The number of Shares that Citadel Securities LLC may be deemed to beneficially own constitutes 0.3% 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 0.6% of the Shares outstanding.
4. The number of Shares that Mr. Griffin may be deemed to beneficially own constitutes 0.6% of the Shares outstanding. %
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| (c) | Number of shares as to which the person has:
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| (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: 0
2. Citadel Securities LLC: 65,617
3. Each of Citadel Securities Group LP and Citadel Securities GP LLC: 145,118
4. Mr. Griffin: 145,118 | ||
| (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: 0
2. Citadel Securities LLC: 65,617
3. Each of Citadel Securities Group LP and Citadel Securities GP LLC: 145,118
4. Mr. Griffin: 145,118 | ||
| Item 5. | Ownership of 5 Percent or Less of a Class. | |
Ownership of 5 percent or less of a class
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| Item 6. | Ownership of more than 5 Percent on Behalf of Another Person. | |
Not Applicable
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| 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
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| Item 8. | Identification and Classification of Members of the Group. | |
Not Applicable
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| Item 9. | Notice of Dissolution of Group. | |
Not Applicable
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| 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.
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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.