[Form 4] Boundless Bio, Inc. Insider Trading Activity

Rhea-AI Filing Summary

Boundless Bio director James Christensen received a grant of stock options, giving him the right to buy 32,000 shares of Common Stock. The options have an exercise price of $1.4000 per share and expire on June 14, 2036.

The award vests in substantially equal monthly installments over the 12 months following June 15, 2026, or earlier on the date of the next annual stockholder meeting if that occurs before June 15, 2027, as long as he continues serving on the board of directors.

Insights

Equity compensation analyst

Routine director option grant with time-based vesting and long-dated expiry.

Director James Christensen received stock options for 32,000 shares of Boundless Bio, Inc. at an exercise price of $1.4000 per share. This is a typical equity compensation award structured as a right to buy common stock in the future.

The options vest in equal monthly installments over the 12 months after June 15, 2026, or fully on the next annual meeting date before June 15, 2027, contingent on continued board service. The options expire on June 14, 2036, giving a long window to exercise.

This filing reports one acquisition-type derivative transaction with 32,000 options outstanding following the grant and no concurrent sales or exercises. It represents routine governance-driven compensation rather than a discretionary market trade, so the directional signal for the stock is limited.

Insider Trade Summary

1 transaction reported

Mixed 1 txn

Insider Christensen James

Role null

Type	Security	Shares	Price	Value
Grant/Award	Stock Option (right to buy)	32,000	$0.00	--

Holdings After Transaction: Stock Option (right to buy) — 32,000 shares (Direct, null)

Footnotes (1)

1. [object Object]

Key Figures

Option grant size: 32,000 options Exercise price: $1.4000 per share Underlying shares: 32,000 shares +3 more

6 metrics

Option grant size 32,000 options Stock Option (right to buy) awarded to director

Exercise price $1.4000 per share Strike price for Boundless Bio common stock

Underlying shares 32,000 shares Common Stock underlying the stock option

Expiration date June 14, 2036 Option expiry for the stock option grant

Vesting period 12 months Monthly vesting after June 15, 2026, or earlier at annual meeting

Shares after transaction 32,000 options Total derivative securities following the grant

Key Terms

Stock Option (right to buy), vesting, annual meeting, board of directors

4 terms

Stock Option (right to buy) financial

"security_title: Stock Option (right to buy)"

vesting financial

"The stock option shall vest in substantially equal monthly installments"

Vesting is the process by which you earn full ownership of something, like company stock or a retirement benefit, over time. It’s like earning the right to keep a gift piece by piece the longer you stay with a company, making sure employees stay committed before they receive all the benefits.

annual meeting financial

"in the event the next annual meeting of the issuer's stockholders occurs"

A company's annual meeting is a yearly gathering where owners (shareholders) and the board review performance, ask questions, and vote on key matters like electing directors, approving auditor choices, and sometimes setting pay or dividend policies. For investors it matters because decisions made and votes cast can change who runs the company, influence strategy and payouts, and affect the value or direction of their investment—similar to a homeowners’ meeting where rules and leaders that shape your property’s value are decided.

board of directors financial

"subject to the reporting person's continuing service on the issuer's board of directors"

The Board of Directors is a group of people chosen by a company's owners to help make big decisions and oversee how the company is run. They act like a team of advisors or managers, making sure the company stays on track and meets its goals. Their choices can influence the company's success and how it grows.

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Form 4 Insider Transactions: What Each Field Means →

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^*

Christensen James

(Last) (First) (Middle)

C/O BOUNDLESS BIO, INC.

11099 NORTH TORREY PINES RD., STE 150

(Street)

LA JOLLA CALIFORNIA 92037

(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)

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

2a. Foreign Trading Symbol

3. Date of Earliest Transaction (Month/Day/Year)
06/15/2026

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

X	Form filed by One Reporting Person
	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

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
Stock Option (right to buy)	$1.4	06/15/2026		A		32,000		(1)	06/14/2036	Common Stock	32,000	$0	32,000	D

Explanation of Responses:

1. The stock option shall vest in substantially equal monthly installments over the 12 months following June 15, 2026 (or, in the event the next annual meeting of the issuer's stockholders occurs prior to June 15, 2027, any remaining unvested portion of the stock option will vest on the date of such annual meeting), subject to the reporting person's continuing service on the issuer's board of directors through such vesting date.

	/s/ Jessica Oien, Attorney-in-Fact for James Christensen	06/15/2026
	** 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)