144 0001753224 XXXXXXXX LIVE 0001722964 Y-mAbs Therapeutics, Inc. 001-38650 202 CARNEGIE CENTER SUITE 301 PRINCETON NJ 08540 646-885-8505 Gad Thomas Officer Director Common Stock Merrill Lynch

225 Liberty St Floor 37 New York NY 10281

10810 56546.86 45218177 03/07/2025 NASDAQ Common Stock 01/17/2025 Vesting of restricted stock unit award Y-mAbs Therapeutics, Inc. N 6993 01/17/2025 Granted as part of issuer equity compensation plan Common Stock 01/18/2025 Vesting of restricted stock unit award Y-mAbs Therapeutics, Inc. N 3817 01/18/2025 Granted as part of issuer equity compensation plan Y 03/07/2025 Thomas Gad