X0609 4 2026-06-18 0001818331 GeneDx Holdings Corp. WGS 0001534264 Casdin Eli false C/O GENEDX HOLDINGS CORP. 333 LUDLOW ST., NORTH TOWER, 6TH FLOOR STAMFORD CT 06902 true false true false 0 Class A Common Stock 2026-06-18 4 M 0 3576 0 A 24093 D Class A Common Stock 3707164 I By Casdin Partners Master Fund, LP Class A Common Stock 19247 I By Casdin Partners GP, LLC Class A Common Stock 333144 I By CMLS Holdings LLC Restricted Stock Unit 2026-06-18 4 A 0 4248 0 A Class A Common Stock 4248 4248 D Restricted Stock Unit 2026-06-18 4 M 0 3576 0 D Class A Common Stock 3576 0 D 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. The securities 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) the Reporting Person, who is the managing member of Casdin and the GP. The securities are owned directly by the GP and may be deemed to be indirectly beneficially owned by the Reporting Person, who is the managing member of the GP. The securities are owned directly by CMLS Holdings LLC ("CMLS Holdings"). The Board of Managers of CMLS Holdings includes the Reporting Person, who, as a member of the Board of Managers of CMLS Holdings, shares voting and investment discretion with respect to securities held by CMLS Holdings. The entire award shall vest on the earlier of the (i) date of the 2027 annual meeting of the Issuer's stockholders, or (ii) first anniversary of the grant date, subject to the Reporting Person's continued service to the Issuer through the vesting date. These RSUs do not have an expiration date; they either vest or are cancelled prior to the vesting date. The entire award vested or vests on the earlier of the: (i) date of the 2026 annual meeting of the Issuer's stockholders, or (ii) first anniversary of the grant date, subject to the Reporting Person's continued service to the Issuer through the vesting date. These RSUs do not have an expiration date; they either vest or are cancelled prior to the vesting date. The Reporting Person disclaims beneficial ownership of the securities reported on this Form 4 except to the extent of his pecuniary interest therein, if any, and this report shall not be deemed an admission that the Reporting Person is the beneficial owner of such securities for purposes of Section 16 under the Securities Exchange Act of 1934, as amended, or for any other purpose. /s/ Bridget Brown, Attorney-in-Fact 2026-06-23