Sec Form 4 Filing - Casdin Eli @ GeneDx Holdings Corp. - 2024-06-20

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 Casdin Eli 2. Issuer Name and Ticker or Trading Symbol GeneDx Holdings Corp. [ WGS] 5. Relationship of Reporting Person(s) to Issuer (Check all applicable) X __ Director X __ 10% Owner _____ Officer (give title below) _____ Other (specify below) (Last) (First) (Middle) C/O GENEDX HOLDINGS CORP., 333 LUDLOW ST, NORTH TOWER 3. Date of Earliest Transaction (MM/DD/YY) 06/20/2024 (Street) STAMFORD, CT06902 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 Class A Common Stock 06/20/2024 M 5,828 A $ 0 ( 1 ) 7,593 D Class A Common Stock 333,144 I See CMLS Holdings LLC ( 2 ) Class A Common Stock 432,902 I See Casdin Partners F01-MSV, LP ( 3 ) Class A Common Stock 3,093,509 I See Casdin Partners Master Fund, LP ( 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 Restricted Stock Unit ( 1 ) 06/20/2024 M 5,828 ( 5 ) ( 5 ) Class A Common Stock 5,828 $ 0 0 D

Reporting Owners Reporting Owner Name / Address Relationships Director 10% Owner Officer Other Casdin Eli C/O GENEDX HOLDINGS CORP. 333 LUDLOW ST, NORTH TOWER STAMFORD, CT06902 X X Signatures /s/ Devin Schaffer, Attorney-in-Fact 06/24/2024 Signature of Reporting Person Date

Explanation of Responses:

( 1 )Each restricted stock unit ("RSU") represents a contingent right to receive 1 share of the Issuer's Class A Common Stock upon settlement for no consideration. ( 2 )The 333,144 shares of Class A Common Stock reported in the table above are owned directly by CMLS Holdings LLC ("CMLS Holdings"). The Board of Managers of CMLS Holdings LLC is comprised of Mr. Casdin and Mr. Keith Meister who share voting and investment discretion with respect to the Class A common stock held of record by CMLS Holdings LLC. C-LSH LLC and M-LSH LLC are the members of CMLS Holdings LLC, and Messrs. Casdin and Meister are the managing members of C-LSH LLC and M-LSH LLC, respectively. As such, Mr. Casdin may be deemed to have or share beneficial ownership of the securities held directly by CMLS Holdings LLC. Each of C-LSH LLC and Mr. Casdin disclaims beneficial ownership of these shares except to the extent of its or his respective pecuniary interest therein. ( 3 )The 432,902 shares of Class A Common Stock reported in the table above are owned directly by Casdin Partners FO1-MSV, LP and may be deemed to be indirectly beneficially owned by (i) Casdin Capital, LLC, the investment adviser to Casdin Partners FO1-MSV, LP, (ii) Casdin Partners GP, LLC, the general partner of Casdin Partners FO1-MSV, LP, and (iii) Mr. Casdin, the managing member of Casdin Capital, LLC and Casdin Partners GP, LLC. Each of Casdin Capital, LLC, Casdin Partners GP, LLC and Mr. Casdin disclaims beneficial ownership of such securities except to the extent of its or his respective pecuniary interest therein. ( 4 )The 3,093,509 shares of Class A Common Stock reported in the table above are owned directly by Casdin Partners Master Fund, L.P. (the "Master Fund") and may be deemed to be indirectly beneficially owned by (i) Casdin Capital, LLC, the investment adviser to the Master Fund ("Casdin"), (ii) Casdin Partners GP, LLC, the general partner of the Master Fund (the "GP"), and (iii) Eli Casdin, the managing member of Casdin and the GP. ( 5 )The RSUs shall vest the earlier of (a) the date of the next annual meeting of the Issuer's shareholders following the grant date, and (b) the first anniversary of the grant date, subject to the Reporting Person continuing to provide services to the Issuer through each vesting 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).

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