Sec Form 4 Filing - MAETZOLD DEREK J @ CASTLE BIOSCIENCES INC - 2019-07-29

FORM 4 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 MAETZOLD DEREK J 2. Issuer Name and Ticker or Trading Symbol CASTLE BIOSCIENCES INC [ CSTL] 5. Relationship of Reporting Person(s) to Issuer (Check all applicable) X __ Director X __ 10% Owner X __ Officer (give title below) _____ Other (specify below) Pres. & Chief Exec. Officer (Last) (First) (Middle) C/O CASTLE BIOSCIENCES, INC., 820 S. FRIENDSWOOD DRIVE, SUITE 201 3. Date of Earliest Transaction (MM/DD/YY) 07/29/2019 (Street) FRIENDSWOOD, TX77546 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 07/29/2019 C 87,264 ( 1 ) A 1,563,884 D Common Stock 07/29/2019 C 8,098 A $ 12.8 ( 3 ) 1,571,982 D Common Stock 164,068 I By trust ( 4 )

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 A Preferred Stock ( 2 ) 07/29/2019 C 102,954 ( 2 ) ( 2 ) Common Stock 84,455 ( 2 ) 0 D Series D Preferred Stock ( 2 ) 07/29/2019 C 530 ( 2 ) ( 2 ) Common Stock 434 ( 2 ) 0 D Series E-2 Preferred Stock ( 2 ) 07/29/2019 C 546 ( 2 ) ( 2 ) Common Stock 447 ( 2 ) 0 D Series E-3 Preferred Stock ( 2 ) 07/29/2019 C 486 ( 2 ) ( 2 ) Common Stock 398 ( 2 ) 0 D Series F Preferred Stock ( 2 ) 07/29/2019 C 1,859 ( 2 ) ( 2 ) Common Stock 1,524 ( 2 ) 0 D Convertible Promissory Note $ 12.8 ( 3 ) 07/29/2019 C ( 3 ) ( 3 ) Common Stock 8,098 ( 3 ) 0 D

Reporting Owners Reporting Owner Name / Address Relationships Director 10% Owner Officer Other MAETZOLD DEREK J C/O CASTLE BIOSCIENCES, INC. 820 S. FRIENDSWOOD DRIVE, SUITE 201 FRIENDSWOOD, TX77546 X X Pres. & Chief Exec. Officer Signatures /s/ Greg Acosta, Attorney-in-fact 07/31/2019 Signature of Reporting Person Date

Explanation of Responses:

( 1 )The shares of Common Stock issued upon conversion of the Preferred Stock were calculated by first aggregating all series of Preferred Stockheld by the Reporting Person, in accordance with the terms of the Company's then-effective Certificate of Incorporation. ( 2 )Every 1.219 outstanding shares of Preferred Stock automatically converted into 1 share of Common Stock immediately prior to the closing of the Issuer's initial public offering (the "IPO"), for no additional consideration, with cash paid for any fractional shares. The Preferred Stock had no expiration date. ( 3 )The principal amount of the Convertible Promissory Note held by the Designated Reporting Person was $100,000. Upon closing of the IPO, all unpaid principal and accrued interest outstanding on the Convertible Promissory Note (the "Conversion Amount") automatically converted into the number of shares of Common Stock equal to the Conversion Amount as of the date immediately prior to the closing date divided by 80% of the IPO price per share of $16.00 per share. ( 4 )Held by the DJM Grantor Retained Annuity Trust No. 1.

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).

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