Sec Form 3 Filing - Sidow Kevin @ CARLSMED, INC. - 2025-07-22

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

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1. Name and Address of Reporting Person Sidow Kevin 2. Issuer Name and Ticker or Trading Symbol CARLSMED, INC. [ CARL] 5. Relationship of Reporting Person(s) to Issuer (Check all applicable) X __ Director _____ 10% Owner _____ Officer (give title below) _____ Other (specify below) (Last) (First) (Middle) C/O CARLSMED, INC., 1800 ASTON AVE., SUITE 100 3. Date of Earliest Transaction (MM/DD/YY) 07/22/2025 (Street) CARLSBAD, CA92008 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

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 Series B Preferred Stock ( 1 ) ( 1 ) ( 1 ) Common Stock 28,900 D Stock Option (Right to Buy) $ 0.33 ( 6 ) ( 3 ) 01/07/2031 Common Stock 51,638 ( 2 ) ( 3 ) D Stock Option (Right to Buy) $ 2.12 ( 6 ) ( 4 ) 05/06/2034 Common Stock 44,802 ( 2 ) ( 4 ) D Stock Option (Right to Buy) $ 5.91 ( 6 ) ( 5 ) 04/09/2035 Common Stock 7,196 ( 2 ) ( 5 ) D

Reporting Owners Reporting Owner Name / Address Relationships Director 10% Owner Officer Other Sidow Kevin C/O CARLSMED, INC. 1800 ASTON AVE., SUITE 100 CARLSBAD, CA92008 X Signatures /s/ Leonard Greenstein, as attorney-in-fact for Kevin Sidow 07/22/2025 Signature of Reporting Person Date

Explanation of Responses:

( 1 )Includes 28,900 shares of Series B Preferred Stock issued to the Reporting Person on April 18, 2022. Each share of Series B Preferred Stock is convertible into one share of the Issuer's common stock immediately prior to the closing of the Issuer's initial public offering. These shares are reported after giving effect to the 1-to-5.58 reverse split of the Issuer's common and preferred stock, effected on July 10, 2025 (the "Reverse Split"). These shares are reported on an as-converted 1-to-1 basis and have no expiration date. ( 2 )These options are reported after giving effect to the Reverse Split of the Issuer's common stock. ( 3 )Includes 51,638 fully vested and exercisable options convertible into approximately 51,638 shares of the Issuer's common stock. ( 4 )Includes 13,067 fully vested and exercisable options convertible into approximately 13,067 shares of the Issuer's common stock, and 31,735 unvested stock options convertible into approximately 31,735 shares of the Issuer's common stock. These options began to vest on May 1, 2024, subject to a one-year cliff, and will be fully vested on May 1, 2028. ( 5 )Includes 7,196 unvested stock options convertible into approximately 7,196 shares of the Issuer's common stock which began to vest on December 31, 2024, subject to a one-year cliff, and will be fully vested on December 31, 2028. ( 6 )The exercise price has been adjusted to reflect the Reverse Split.

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).

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