Eleventh Amendment to Lease by and between the Company and University of Massachusetts Dartmouth dated as of December 1, 2024

Exhibit 10.12

ELEVENTH AMENDMENT TO LEASE

This ELEVENTH AMENDMENT TO LEASE (this “Amendment”) is made as of the 1^st day of December, 2024, (the “Effective Date”) by and between UNIVERSITY OF MASSACHUSETTS DARTMOUTH, an institution of Higher Education of the Commonwealth of Massachusetts, with an address of 285 Old Westport Rd. North Dartmouth Massachusetts 02747 (“Landlord”) and CELLDEX THERAPEUTICS, INC. (formerly AVANT Immunotherapeutic, Inc.), a Delaware corporation, with an address of 53 Frontage Road, Hampton NJ 08827 (“Tenant”).

RECITALS

WHEREAS, Tenant and the Massachusetts Development Finance Agency (“MDFA”) entered into a certain Lease dated effective December 22, 2003 ( the “Lease), as amended by that certain First Amendment to Lease dated as of March 17, 2005 (the “First Amendment”), that certain Second Amendment to Lease dated as of November 4, 2005 (the “Second Amendment”), that certain Third Amendment To Lease dated as of December 20, 2006 (the “Third Amendment”), that certain Fourth Amendment to Lease dated as of July 18, 2008 (the “Fourth Amendment”), that certain Fifth Amendment to Lease dated as of October 3, 2008 (the “Fifth Amendment”), that certain Sixth Amendment to Lease dated as of August 20, 2009 (the “Sixth Amendment”), that certain Seventh Amendment to Lease dated June 22, 2010 (the “Seventh Amendment”), that certain Eight Amendment to lease dated November 15, 2015 (the “Eight Amendment”), that certain Ninth Amendment to lease dated, October 1, 2019 (the “Ninth Amendment”), and that certain Tenth Amendment to the lease dated August 1, 2022 (the “Tenth Amendment”) of certain premises consisting of approximately 33,931 rentable square feet of space (the “Premises”) in the building (the “Building”) located at 151 Martine Street,

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Fall River, Massachusetts (the “Property”) in the South Coast Research & Technology Park (the “Park”); and

WHEREAS, on June 24, 2014, MDFA conveyed all of its rights, title and interest in the Building and assigned the Lease to Landlord; and

WHEREAS, the Premises is comprised of: (i) the original premises demised by the Lease, as amended through the Third Amendment, being 11,756 rentable square feet on the second (2nd) floor of the Building, (ii) the Additional Space (as defined in the First Amendment) demised by the First Amendment, being 71 rentable square feet on the first (1st) floor of the Building, (iii) the Expansion Premises (as defined in the Second Amendment), being 2,487 rentable square feet on the second (2nd) floor of the Building; (iv) the Second Expansion Premises (as defined in the Third Amendment), being 1,853 rentable square feet on the second (2nd) floor of the Building; (v) the Substitute Third Expansion Premises (as defined in the Fifth Amendment), being 4,864 rentable square feet of space on the second floor of the Building (referred to therein as the “Third Expansion Premises”); (vi) the Fourth Expansion Premises (as defined in the Sixth Amendment), being 2,382 rentable square feet on the second (2nd) floor of the Building; (vii) the Fifth Expansion Premises (as defined in the Eight Amendment), being 5,511 rentable square feet on the second (2^nd) floor of the Building, and (viii) the Sixth Expansion Premises ( as defined in the Ninth Amendment), being 5,007 rentable square feet - 4,686 rentable square feet on the first (1st) floor of the building and 321 rentable square feet on the second (2nd) floor of the Building such that the “Premises Square Footage” (as stated in the Ninth Amendment) is defined to be 33,931 rentable square feet; and

WHEREAS, Landlord and Tenant agree to enter into this Eleventh Amendment to the Lease to extend the term of the lease and to amend certain additional provisions of the Lease,

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NOW, THEREFORE, for good and valuable consideration, the receipt and sufficiency of which is hereby mutually acknowledged, Landlord and Tenant agree as follows:

1.Capitalized Terms. Unless otherwise defined herein, all capitalized terms used in this Amendment shall have the meanings ascribed to them in the Lease, and all references in the Lease to the “Lease” or “this Lease” or “herein” or “hereunder” or similar terms or to any Section thereof shall, after the Effective Date, mean the Lease, or such Section thereof, as amended by this Amendment.

2.Section 2.2. Term. Section 2.2 of the Lease shall be amended as of December 1, 2024 to read as follows:”Section 2.2 Term. TO HAVE AND TO HOLD for a term (the “Term”) beginning on the Term Commencement Date which shall be August 1, 2022 and expiring on July 31, 2027 (the “Term Expiration Date”), unless earlier terminated as provided for in section 2.4”

3.Annual Fixed Rental Rate. Section 1.1 as of December 1, 2024 the Lease is amended by deleting the provisions regarding the “Annual Fixed Rental Rate” and inserting, the following language:

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4.Demise of Seventh Expansion Premises. Commencing on December 1, 2024 (“The Seventh Expansion Premise Commencement Date”), Landlord does hereby lease to Tenant and Tenant does lease from Landlord the approximately 2418 rentable square feet - 1,333 rentable square feet on the first (1st) floor of the building and 1,085 rentable square feet on the second (2nd) floor of the Building, as shown on the floor plan attached hereto as Exhibit A-10 (the “Seventh Expansion Premises”) to have and to hold for the remainder of the Lease Term as set forth in the Lease. Tenant shall have access to the Seventh Expansion Premises as of December 1, 2024. Rental fee shall commence on December 1, 2024. Any delay in access to all Seventh Expansion Premises will result in similar delay in rent commencement. Except as otherwise expressly provided herein, Tenant’s lease of the Seventh Expansion Premises shall be on all of the terms and conditions of the Lease (including, without limitation, extension rights of Tenant for Extension Terms) and the term of the Lease with respect to the Seventh Expansion Premises shall be coterminous with the Term (and, if exercised, Extension Terms) of the Lease for the Existing Premises. As of the Seventh Expansion Premises Commencement Date, all references in the Lease to (i) the “Premises” and/or premises demised by the Lease shall mean the Existing Premises and the Seventh Expansion Premises collectively as shown on Exhibit A to the Lease, Exhibit A-1, attached to the First Amendment , Exhibit A-2, attached to the Second Amendment, Exhibit A-3, attached to the Third Amendment, and on Exhibit A-5, attachead to the Fifth Amendment, Exhibit A-6, attached to the Sixth Amendment, Exhibit A-7, attached to the Seventh Amendment, Exhibit A-8 attached to the Eight Amendment, Exhibit A-9 attached to 9^th Amendment and Exhibit A-10 attached to this amendment; (ii) the “Tenant’s Proportionate Fraction” as set forth in Section 1.1, “Reference Information”, of the Lease shall mean 63.24% which is calculated by adding the Premises Square Footage as set forth in the

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Eight Amendment and the Seventh Expansion Premises and dividing the Building’s rentable square foot into that sum; and (iii) the “Premises Square Footage shall mean 36,349 rentable square feet.

5.The parties agree that License agreement dated July 13, 2020 is terminated as of December 1, 2024.

6.Landlord Representation Regarding Environmental Hazards. To its knowledge, Landlord represents that there are no environmental hazards or violations of any environmental laws, regulations or ordinances in or around the Building which violations might pose a present danger to health, life or safety.

7.Non-disturbance of Tenancy. Landlord represents that it has no financing on the Building whereby Landlord’s lender would be entitled to disturb the tenancy of Tenant upon a default therein Landlord. Landlord further represents that it shall not enter into any such financing, but rather shall negotiate with any such lender so as to permit Tenant to remain in possession of the Premises on a direct rental relationship with such lender so long as Tenant is not in default of its obligations under this Lease.

8.Ratification. Except as expressly modified by this Amendment, the Lease shall remain in full force and effect, and as further modified by this Amendment, is expressly ratified and confirmed by the parties hereto. This Amendment shall be binding upon and inure to the benefit of the parties hereto and their respective successors and assigns, subject to the provisions of the Lease regarding assignment and subletting.

9.Governing Law; Interpretation; and Partial Invalidity. This Amendment shall be governed and construed in accordance with the laws of the Commonwealth of Massachusetts. If any term of this Amendment, or the application thereof to any person or circumstances, shall

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to any extent be invalid or unenforceable, the remainder of this Amendment, or the application of such term to persons or circumstances other than those as to which it is invalid or unenforceable, shall not be affected thereby, and each term of this Amendment shall be valid and enforceable to the fullest extent permitted by law. The titles for the paragraphs are for convenience only and not to be considered in construing this Amendment. This Amendment contains all of the agreements of the parties with respect to the subject matter hereof, and supersedes all prior dealings between them with respect to such subject matter. No delay or omission on the part of either party to this Amendment in requiring performance by the other party or exercising any right hereunder shall operate as a waiver of any provision hereof or any rights hereunder, and no waiver, omission or delay in requiring performance or exercising any right hereunder on any one occasion shall be construed as a bar to or waiver of such performance or right on any future occasion.

10.Counterparts and Authority, This Amendment may be executed in multiple counterparts, each of which shall be deemed an original and all of which together shall constitute one and the same document. Landlord and Tenant each warrant to the other that the person or persons executing this Amendment on its behalf has or have authority to do so and that such execution has fully obligated and bound such party to all terms and provisions of this Amendment.

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IN WITNESS WHEREOF, the undersigned executed this Amendment as of the date and year first written above.

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