SCHEDULE 13G/A 0001766853 XXXXXXXX LIVE 3 Common stock, par value $0.0001 per share 08/19/2025 0001722964 Y-mAbs Therapeutics, Inc. 984241109 202 CARNEGIE CENTER SUITE 301 PRINCETON NJ 08540 Rule 13d-1(c) ACORN BIOVENTURES, L.P. b DE 0.00 1175686.00 0.00 1175686.00 1175686.00 2.6 PN ACORN CAPITAL ADVISORS GP, LLC b DE 0.00 1175686.00 0.00 1175686.00 1175686.00 2.6 OO ACORN BIOVENTURES 2, L.P. b DE 0.00 1620611.00 0.00 1620611.00 1620611.00 3.6 PN Acorn Capital Advisors GP 2, LLC b DE 0.00 1620611.00 0.00 1620611.00 1620611.00 3.6 OO Anders Hove b X1 0.00 2796297.00 0.00 2796297.00 2796297.00 6.2 IN Y-mAbs Therapeutics, Inc. 202 CARNEGIE CENTER, SUITE 301, PRINCETON, NEW JERSEY, 08540. Acorn Bioventures, L.P. Acorn Capital Advisors GP, LLC Acorn Bioventures 2, L.P. Acorn Capital Advisors GP 2, LLC Anders Hove 420 Lexington Avenue, Suite 2626, New York, New York 10170 Acorn Bioventures, L.P. and Acorn Bioventures 2 L.P. are both Delaware limited partnerships. Acorn Capital Advisors GP, LLC and Acorn Capital Advisors GP 2, LLC are both Delaware limited liability companies. Anders Hove is a citizen of the United States of America. N The information required by Items 4(a) - (c) is set forth in Rows (5) - (11) of the cover page for each Reporting Person hereto and is incorporated herein by reference for each Reporting Person. The percentages set forth herein are calculated based upon 45,438,420 shares of Common Stock outstanding as of August 4, 2025 as reported in the Issuer's Quarterly Report on Form 10-Q for the quarterly period ended June 30, 2025 filed with the Securities and Exchange Commission on August 8, 2025. Acorn Capital Advisors GP, LLC is the General Partner of Acorn Bioventures, LP and may be deemed to beneficially own the shares of Common Stock beneficially owned by Acorn Bioventures, LP. Acorn Capital Advisors GP 2, LLC is the General Partner of Acorn Bioventures 2, L.P. and may be deemed to beneficially own the shares of Common Stock beneficially owned by Acorn Bioventures 2, L.P. Anders Hove, in his capacity as Manager of each of Acorn Capital Advisors GP, LLC and Acorn Capital Advisors GP 2, LLC, may be deemed to beneficially own the shares beneficially owned by each of Acorn Capital Advisors GP, LLC and Acorn Capital Advisors GP 2, LLC. 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 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. ACORN BIOVENTURES, L.P. Anders Hove 08/20/2025 ACORN CAPITAL ADVISORS GP, LLC Anders Hove 08/20/2025 ACORN BIOVENTURES 2, L.P. Anders Hove 08/20/2025 Acorn Capital Advisors GP 2, LLC Anders Hove 08/20/2025 Anders Hove Anders Hove 08/20/2025