SCHEDULE 13G/A 0000902664-25-002308 0001727492 XXXXXXXX LIVE 1 Common stock, par value $0.0001 per share 09/30/2025 0001722964 Y-mAbs Therapeutics, Inc. 984241109 202 CARNEGIE CENTER SUITE 301 PRINCETON NJ 08540 Rule 13d-1(b) Caligan Partners LP DE 0.00 0.00 0.00 0.00 0.00 N 0 IA PN David Johnson X1 0.00 0.00 0.00 0.00 0.00 N 0 HC IN Y-mAbs Therapeutics, Inc. 202 Carnegie Center, Suite 301 Princeton, NJ 08540 This statement is filed by: (i) Caligan Partners LP, a Delaware limited partnership ("Caligan"), which serves indirectly as the investment manager to Caligan Partners Master Fund LP, a Cayman Islands limited partnership (the "Caligan Fund") and a managed account (the "Caligan Account"), with respect to the shares of common stock, par value $0.0001 per share ("Common Stock") of Y-mAbs Therapeutics, Inc., a Delaware corporation, that were held by the Caligan Fund and Caligan Account; and (ii) David Johnson, the Managing Partner of Caligan and Managing Member of Caligan Partners GP LLC, the general partner of Caligan ("Mr. Johnson"), with respect to the shares of Common Stock that were held by the Caligan Fund and Caligan Account. Each of the foregoing is referred to as a "Reporting Person" and collectively as the "Reporting Persons." The principal business address of each of the Reporting Persons is 780 Third Avenue, 30th Floor, New York, NY 10017. Caligan is a Delaware limited partnership. Mr. Johnson is a United States citizen. N IA HC The information required by Item 4(a) is set forth in Row 9 of the cover page for each of the Reporting Persons and is incorporated herein by reference. 0% The information required by Item 4(c)(i) is set forth in Row 5 of the cover page for each of the Reporting Persons and is incorporated herein by reference. The information required by Item 4(c)(ii) is set forth in Row 6 of the cover page for each of the Reporting Persons and is incorporated herein by reference. The information required by Item 4(c)(iii) is set forth in Row 7 of the cover page for each of the Reporting Persons and is incorporated herein by reference. The information required by Item 4(c)(iv) is set forth in Row 8 of the cover page for each of the Reporting Persons and is incorporated herein by reference. N Y Y Y Y Y N By signing below I certify that, to the best of my knowledge and belief, the securities referred to above were acquired and are held in the ordinary course of business and were not acquired and are not held for the purpose of or with the effect of changing or influencing the control of the issuer of the securities and were not acquired and are not held in connection with or as a participant in any transaction having that purpose or effect, other than activities solely in connection with a nomination under ?? 240.14a-11. Caligan Partners LP /s/ David Johnson 11/14/2025 David Johnson /s/ David Johnson 11/14/2025