Statement of Changes in Beneficial Ownership (Form 4)

FORM 4 Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b). Check this box to indicate that a transaction was made pursuant to a contract, instruction or written plan that is intended to satisfy the affirmative defense conditions of Rule 10b5-1(c). See Instruction 10.

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP OF SECURITIES Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934 or Section 30(h) of the Investment Company Act of 1940

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1. Name and Address of Reporting Person * TANG KEVIN 2. Issuer Name and Ticker or Trading Symbol Boundless Bio, Inc. [BOLD] 5. Relationship of Reporting Person(s) to Issuer (Check all applicable) _____ Director __X__ 10% Owner _____ Officer (give title below) _____ Other (specify below) (Last) (First) (Middle) 4747 EXECUTIVE DRIVE, SUITE 210 3. Date of Earliest Transaction (Month/Day/Year) 06/25/2026 (Street) SAN DIEGO, CA 92121 4. If Amendment, Date Original Filed (Month/Day/Year) 6. Individual or Joint/Group Filing (Check Applicable Line) ___ Form filed by One Reporting Person _X_ Form filed by More than One Reporting Person (City) (State) (Zip) Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned

1.Title of Security (Instr. 3) 2. Transaction Date (Month/Day/Year) 2A. Deemed Execution Date, if any (Month/Day/Year) 3. Transaction Code (Instr. 8) 4. Securities Acquired (A) or Disposed of (D) (Instr. 3, 4 and 5) 5. Amount of Securities Beneficially Owned Following Reported Transaction(s) (Instr. 3 and 4) 6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4) 7. Nature of Indirect Beneficial Ownership (Instr. 4) Code V Amount (A) or (D) Price Common Stock 06/25/2026 P 145,880 A $2.48(1) 2,393,392 I By LP(2) Common Stock 06/25/2026 P 510 A $2.56(3) 2,393,902 I By LP(2) Common Stock 06/26/2026 P 75,047 A $2.55(4) 2,468,949 I By LP(2) Common Stock 06/26/2026 P 134 A $2.54(5) 2,469,083 I By LP(2) Common Stock 06/29/2026 P 63,985 A $2.47(6) 2,533,068 I By LP(2) Common Stock 06/29/2026 P 777 A $2.48(7) 2,533,845 I By LP(2)

Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.
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Table II - Derivative Securities Acquired, Disposed of, or Beneficially Owned
(e.g., puts, calls, warrants, options, convertible securities)

1. Title of Derivative Security (Instr. 3)

2. Conversion or Exercise Price of Derivative Security

3. Transaction Date (Month/Day/Year)

3A. Deemed Execution Date, if any (Month/Day/Year)

4. Transaction Code (Instr. 8)

5. Number of Derivative Securities Acquired (A) or Disposed of (D) (Instr. 3, 4, and 5)

6. Date Exercisable and Expiration Date (Month/Day/Year)

7. Title and Amount of Underlying Securities (Instr. 3 and 4)

8. Price of Derivative Security (Instr. 5)

9. Number of Derivative Securities Beneficially Owned Following Reported Transaction(s) (Instr. 4)

10. Ownership Form of Derivative Security: Direct (D) or Indirect (I) (Instr. 4)

11. Nature of Indirect Beneficial Ownership (Instr. 4)

Code

V

(A)

(D)

Date Exercisable

Expiration Date

Title

Amount or Number of Shares

Reporting Owners

Reporting Owner Name / Address	Relationships
	Director	10% Owner	Officer	Other
TANG KEVIN 4747 EXECUTIVE DRIVE SUITE 210 SAN DIEGO, CA 92121		X
TANG CAPITAL MANAGEMENT LLC 4747 EXECUTIVE DRIVE SUITE 210 SAN DIEGO, CA 92121		X

Signatures

Kevin Tang		06/29/2026
**Signature of Reporting Person		Date
Kevin Tang, Manager		06/29/2026
**Signature of Reporting Person		Date

Explanation of Responses:

*	If the form is filed by more than one reporting person, see Instruction 4(b)(v).
**	Intentional misstatements or omissions of facts constitute Federal Criminal Violations. See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).
(1)	The prices reported are weighted-average prices. These shares were purchased in multiple transactions at prices ranging from $2.42 to $2.56. The Reporting Persons undertake to provide the Issuer, any security holder of the Issuer or the SEC staff, upon request, all information regarding the number of shares purchased at each price within the ranges set forth in Footnotes 1 and 3 through 7.
(2)	Tang Capital Partners, LP ("TCP") beneficially owns 580,669 shares, Tang Capital Partners International, LP ("TCPI") beneficially owns 791,839 shares, Tang Capital Partners III, Inc. ("TCP III") beneficially owns 580,668 shares, and Tang Capital Partners IV, Inc. ("TCP IV") beneficially owns 580,669 shares. Kevin Tang is the sole manager of Tang Capital Management, LLC, which is the general partner of TCP and TCPI. Kevin Tang is the sole director and Chief Executive Officer of TCP III and TCP IV, which are indirectly wholly owned by TCP. Mr. Tang has a pecuniary interest in the shares beneficially held by TCP, TCPI, TCP III and TCP IV.
(3)	These shares were purchased in multiple transactions at prices ranging from $2.53 to $2.60.
(4)	These shares were purchased in multiple transactions at prices ranging from $2.46 to $2.60.
(5)	These shares were purchased in multiple transactions at prices ranging from $2.52 to $2.58.
(6)	These shares were purchased in multiple transactions at prices ranging from $2.40 to $2.59.
(7)	These shares were purchased in multiple transactions at prices ranging from $2.44 to $2.52.

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