Boundless Bio owners buy 10,707 common shares

The purchase was not reported as made under a Rule 10b5-1 plan.

Available on EDGAR 10/29/2026 - 06:21 PM EDT Accepted by SEC EDGAR 10/29/2026 - 06:20 PM EDT Learn about SEC filing dates

Rhea-AI Filing Summary

Boundless Bio, Inc. (BOLD) ten-percent owners Kevin Tang and Tang Capital Management LLC reported an indirect purchase of 10,707 common shares on October 27, 2026, at a weighted-average $2.40 per share (prices ranged from $2.38 to $2.40). The reported resulting holding was 3,022,456 shares. Footnotes identify Tang Capital Partners, LP, Tang Capital Partners International, LP, Tang Capital Partners III, Inc. and Tang Capital Partners IV, Inc. as beneficial owners; Kevin Tang has a pecuniary interest in those shares.

Insider Trade Summary

Net Buyer: 10,707 shares

Net Buy 1 txn

Insider TANG KEVIN, TANG CAPITAL MANAGEMENT LLC

Role 10% Owner | 10% Owner

Bought 10,707 shs ($26K)

Type	Security	Shares	Price	Value
Purchase	Common Stock F1, F2	10,707	$2.40	$26K

Holdings After Transaction: Common Stock — 3,022,456 shares (Indirect, See Footnote)

Footnotes (2)

1. F1. The prices reported are weighted-average prices. These shares were purchased in multiple transactions at prices ranging from $2.38 to $2.40. 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 range set forth in Footnote 1.
2. F2. Tang Capital Partners, LP ("TCP") beneficially owns 691,177 shares, Tang Capital Partners International, LP ("TCPI") beneficially owns 961,511 shares, Tang Capital Partners III, Inc. ("TCP III") beneficially owns 691,170 shares, and Tang Capital Partners IV, Inc. ("TCP IV") beneficially owns 678,598 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.

Key Figures

Common shares purchased: 10,707 shares Weighted-average price: $2.40 per share Purchase price range: $2.38 to $2.40 per share +1 more

4 metrics

Common shares purchased 10,707 shares October 27, 2026

Weighted-average price $2.40 per share October 27, 2026 purchase

Purchase price range $2.38 to $2.40 per share Multiple transactions

Shares following transaction 3,022,456 shares Reported after the October 27, 2026 purchase

Key Terms

weighted-average prices, beneficially owns, pecuniary interest, general partner

4 terms

weighted-average prices financial

"The prices reported are weighted-average prices"

beneficially owns regulatory

"Tang Capital Partners, LP beneficially owns 691,177 shares"

Beneficially owns means a person or entity enjoys the economic benefits and control of a security even if the legal title or registration is held in another name. Think of it like having the keys and profits from a car that is registered to a friend: you use it, benefit from it, and make decisions about it even though the official paperwork lists someone else. For investors, this matters because it reveals who truly controls shares, affects voting power, potential conflicts of interest, and regulatory disclosure obligations.

pecuniary interest regulatory

"Mr. Tang has a pecuniary interest in the shares"

general partner technical

"Tang Capital Management, LLC, which is the general partner of TCP and TCPI"

A general partner is the person or firm that runs an investment partnership and legally represents it — they make the day-to-day decisions, choose which assets to buy or sell, and are responsible for the partnership’s obligations. Investors care because the general partner’s judgment, risk-taking and fee and profit-sharing arrangements determine both the potential returns and the level of exposure to losses; think of the GP as the ship’s captain whose skill and honesty shape the voyage’s outcome.

FAQ

AI-generated questions and answers. How Rhea-AI works. Not financial advice.

How many shares did BOLD ten-percent owners buy?

Kevin Tang and Tang Capital Management LLC reported an indirect purchase of 10,707 common shares on October 27, 2026, at a weighted-average price of $2.40 per share, with purchase prices ranging from $2.38 to $2.40. The reported resulting holding was 3,022,456 shares. No Rule 10b5-1 plan is reported for the purchase.

AI-generated analysis. How Rhea-AI works. Not financial advice.

Form 4 Insider Transactions: What Each Field Means →

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SEC Form 4

FORM 4

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

STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP

Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934
or Section 30(h) of the Investment Company Act of 1940

OMB APPROVAL

OMB Number:			3235-0287
Estimated average burden
hours per response:			0.5

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 for the purchase or sale of equity securities of the issuer that is intended to satisfy the affirmative defense conditions of Rule 10b5-1(c). See Instruction 10.

1. Name and Address of Reporting Person^*

TANG KEVIN

(Last) (First) (Middle)

4747 EXECUTIVE DRIVE

SUITE 210

(Street)

SAN DIEGO CALIFORNIA 92121

(City) (State) (Zip)

UNITED STATES

(Country)

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)

2a. Foreign Trading Symbol

3. Date of Earliest Transaction (Month/Day/Year)
10/27/2026

6. Individual or Joint/Group Filing (Check Applicable Line)

	Form filed by One Reporting Person
X	Form filed by More than One Reporting Person

4. If Amendment, Date of Original Filed (Month/Day/Year)

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	10/27/2026		P		10,707	A	$2.4(1)	3,022,456	I	See Footnote(2)

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 Securities Underlying Derivative Security (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: 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

1. Name and Address of Reporting Person^*

TANG KEVIN

(Last) (First) (Middle)

4747 EXECUTIVE DRIVE

SUITE 210

(Street)

SAN DIEGO CALIFORNIA 92121

(City) (State) (Zip)

UNITED STATES

(Country)

Relationship of Reporting Person(s) to Issuer

	Director	X	10% Owner
	Officer (give title below)		Other (specify below)

1. Name and Address of Reporting Person^*

TANG CAPITAL MANAGEMENT LLC

(Last) (First) (Middle)

4747 EXECUTIVE DRIVE

SUITE 210

(Street)

SAN DIEGO CALIFORNIA 92121

(City) (State) (Zip)

UNITED STATES

(Country)

Relationship of Reporting Person(s) to Issuer

	Director	X	10% Owner
	Officer (give title below)		Other (specify below)

Explanation of Responses:

1. The prices reported are weighted-average prices. These shares were purchased in multiple transactions at prices ranging from $2.38 to $2.40. 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 range set forth in Footnote 1.

2. Tang Capital Partners, LP ("TCP") beneficially owns 691,177 shares, Tang Capital Partners International, LP ("TCPI") beneficially owns 961,511 shares, Tang Capital Partners III, Inc. ("TCP III") beneficially owns 691,170 shares, and Tang Capital Partners IV, Inc. ("TCP IV") beneficially owns 678,598 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.

	Kevin Tang	10/29/2026
	Kevin Tang, Manager	10/29/2026
	** Signature of Reporting Person	Date
Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.
* 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).
Note: File three copies of this Form, one of which must be manually signed. If space is insufficient, see Instruction 6 for procedure.
Persons who respond to the collection of information contained in this form are not required to respond unless the form displays a currently valid OMB Number.
* Form 4: SEC 1474 (03-26)