Item 1.01 Entry into a Material Definitive Agreement.

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On September 11, 2024, Y-mAbs Therapeutics, Inc. (the "Company") entered into a lease agreement (the "Lease") with Princeton 202 Associates Limited Partnership (the "Lessor") for approximately 10,817 square feet located at 202 Carnegie Center, Princeton, New Jersey (the "Premises"). The Company intends to use the Premises as its corporate headquarters once it transfers to the Premises, which it expects to do in the first half of 2025. The term of the Lease will commence once the fitout of the Premises is complete and the Company takes possession of the space and will expire 10 years and nine months after such date. The Company has two options to extend the Lease, each for an additional five-year term. The Lease provides for approximately 5,040 square feet of office space in the same location as the Premises that is available for immediate occupancy and until the fitout of the Premises is complete. The aggregate estimated base rent payment due over the initial term of the Lease is approximately $3.9 million.

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The Lease contains customary provisions requiring the Company to pay its pro rata share of operating expenses and certain taxes and fees related to the Premises and provisions allowing the Lessor to terminate the Lease upon the occurrence of certain customary Company events of default.

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The foregoing description of the Lease is qualified in its entirety by reference to the Lease, a copy of which will be filed as an exhibit to the Company's Quarterly Report on Form 10-Q for the quarter ending September 30, 2024.

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