X0306 4 2020-06-23 0 0001722964 Y-mAbs Therapeutics, Inc. YMAB 0001751804 Hamill Laura C/O Y-MABS THERAPEUTICS, INC. 230 PARK AVENUE SUITE 3350 NEW YORK NY 10169 1 0 0 0 Non-Employee Stock Option (right to buy) 48.67 2020-06-23 4 A 0 32000 0 A 2020-07-23 2030-06-23 Common stock 32000 32000 D Stock options granted to the Reporting Person as a non-employee director pursuant to the 2018 Equity Incentive Plan of Y-mAbs Therapeutics, Inc. The stock options vest in equal monthly installments until the third anniversary of the date of grant, subject to the Reporting Person's continued service on the board of directors of Y-mAbs Therapeutics, Inc., and are exercisable immediately upon vesting. /s/ Laura Hamill 2020-06-24