Sec Form 3 Filing - HINKLE DAVID A @ Boundless Bio, Inc. - 2024-10-11

FORM 3 Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).

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, Section 17(a) of the Public Utility Holding Company Act of 1935 or Section 30(h) of the Investment Company Act of 1940

OMB APPROVAL OMB Number: 3235-0287 Expires: November 30, 2011 Estimated average burden hours per response... 0.5

1. Name and Address of Reporting Person HINKLE DAVID A 2. Issuer Name and Ticker or Trading Symbol Boundless Bio, Inc. [ BOLD] 5. Relationship of Reporting Person(s) to Issuer (Check all applicable) _____ Director _____ 10% Owner X __ Officer (give title below) _____ Other (specify below) See Remarks (Last) (First) (Middle) C/O BOUNDLESS BIO, INC., 9880 CAMPUS POINT DRIVE, SUITE 120 3. Date of Earliest Transaction (MM/DD/YY) 10/11/2024 (Street) SAN DIEGO, CA92121 4. If Amendment, Date Original Filed (MM/DD/YY) 6. Individual or Joint/Group Filing (Check Applicable Line) __ X __ Form filed by One Reporting Person _____ 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 (MM/DD/YY) 2A. Deemed Execution Date, if any (MM/DD/YY) 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 100 D

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 (MM/DD/YY) 3A. Deemed Execution Date, if any (MM/DD/YY) 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 (MM/DD/YY) 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 Stock Option ( 8 ) ( 9 ) ( 1 ) 06/01/2031 Common Stock 21,794 D Stock Option ( 8 ) ( 9 ) ( 2 ) 06/06/2031 Common Stock 9,642 D Stock Option ( 8 ) ( 9 ) ( 3 ) 12/05/2031 Common Stock 10,256 D Stock Option ( 8 ) ( 9 ) ( 4 ) 06/12/2033 Common Stock 23,076 D Stock Option ( 8 ) ( 9 ) ( 5 ) 06/12/2033 Common Stock 12,819 D Stock Option ( 8 ) ( 9 ) ( 6 ) 02/14/2034 Common Stock 22,658 D Stock Option ( 8 ) ( 9 ) ( 7 ) 03/26/2034 Common Stock 13,915 D

Reporting Owners Reporting Owner Name / Address Relationships Director 10% Owner Officer Other HINKLE DAVID A C/O BOUNDLESS BIO, INC. 9880 CAMPUS POINT DRIVE, SUITE 120 SAN DIEGO, CA92121 See Remarks Signatures /s/ Jessica Oien, Attorney- in-Fact for David A. Hinkle 10/15/2024 Signature of Reporting Person Date

Explanation of Responses:

( 1 )The stock option vested as to 25% of the underlying shares on June 1, 2022, and vests as to the remaining underlying shares in 36 substantially equal monthly installments thereafter. ( 2 )The stock option vests in 48 substantially equal monthly installments of the original number of underlying shares, which was 9,742 shares. The first installment vested on July 7, 2021. Prior to October 11, 2024, the reporting person partially exercised the stock option and purchased 100 of the underlying shares which had vested. ( 3 )The stock option vests in 48 substantially equal monthly installments. The first installment vested on January 6, 2022. ( 4 )The stock option vests in 48 substantially equal monthly installments. The first installment vested on July 13, 2023. ( 5 )The stock option vests in 48 substantially equal monthly installments. The first installment vested on July 13, 2023. ( 6 )The stock option vests in 48 substantially equal monthly installments. The first installment vested on March 15, 2024. ( 7 )The stock option vests in 48 substantially equal monthly installments. The first installment vested on April 27, 2024. ( 8 )The issuer repriced the stock option on August 19, 2024 (the "Repricing Date"). As of the Repricing Date, the exercise price was reduced to $3.56 per share, representing the fair market value per share of the issuer's common stock on the Repricing Date; provided, however, that the original exercise price before the repricing will apply if, prior to the Premium End Date (as defined below), the stock option is exercised or the reporting person's employment terminates for any reason other than a Qualifying Termination (as defined below). The "Premium End Date" means the earliest of: (i) August 19, 2026, (ii) the date immediately prior to the closing of a change in control, or (iii) the date of the reporting person's Qualifying Termination. A "Qualifying Termination" means (a) the involuntary termination of the reporting person's employment by the issuer due to a reduction in force (and other than for cause), ( 9 )(Continued from footnote 8) or (b) the reporting person's termination of employment due to death or disability. The original exercise price (before the repricing) of each stock option that expires in 2031 or 2033 was $4.10 per share. The original exercise price of the stock option that expires in February 2034 was $8.19 per share, and the original exercise price of the stock option that expires in March 2034 was $16.00 per share.

Remarks: Sr. VP, Finance, Controller, Treasurer Exhibit 24 - Power of Attorney.

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.