UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM 8-K

CURRENT REPORT

Pursuant to Section 13 or 15(d)
of the Securities Exchange Act of 1934

Date of Report (Date of earliest event reported): July 10, 2026

Celldex Therapeutics, Inc.

(Exact name of registrant as specified in its charter)

Delaware		000-15006		13-3191702
(State or other jurisdiction of incorporation)		(Commission File Number)		(IRS Employer Identification No.)

Perryville III Building, 53 Frontage Road, Suite 220,

Hampton, New Jersey 08827

(Address of principal executive offices) (Zip Code)

(908) 200-7500

(Registrant’s telephone number, including area code)

Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions:

¨	Written communications pursuant to Rule 425 under the Securities Act (17 CFR 230.425)

¨	Soliciting material pursuant to Rule 14a-12 under the Exchange Act (17 CFR 240.14a-12)

¨	Pre-commencement communications pursuant to Rule 14d-2(b) under the Exchange Act (17 CFR 240.14d-2(b))

¨	Pre-commencement communications pursuant to Rule 13e-4(c) under the Exchange Act (17 CFR 240.13e-4(c))

Securities registered pursuant to Section 12(b) of the Act:

Title of each class	Trading Symbol(s)	Name of each exchange on which registered
Common Stock, par value $.001	CLDX	Nasdaq Capital Market

Indicate by check mark whether the registrant is an emerging growth company as defined in Rule 405 of the Securities Act of 1933 (17 CFR §230.405) or Rule 12b-2 of the Securities Exchange Act of 1934 (17 CFR §240.12b-2).

Emerging growth company ¨

If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act. ¨

Item 5.02. Departure of Directors or Certain Officers; Election of Directors; Appointment of Certain Officers; Compensatory Arrangements of Certain Officers.

On July 10, 2026, Sam Martin, Senior Vice President and Chief Financial Officer of Celldex Therapeutics, Inc. (the “Company”), notified the Company of his plans to retire effective on or about March 31, 2027. Mr. Martin joined the Company in April 2009 and has served as Chief Financial Officer since July 2017. The Company has initiated a search for a new Chief Financial Officer. To ensure a smooth transition of his responsibilities, Mr. Martin intends to continue to serve the Company as Chief Financial Officer through March 31, 2027 or until such earlier time as his successor begins to serve in such capacity.

Item 9.01. Financial Statements and Exhibits.

Exhibit No.		Description

104		Cover Page Interactive Data File (embedded within the Inline XBRL document)

-2-

SIGNATURES

Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized.

	CELLDEX THERAPEUTICS, INC.

Dated: July 15, 2026	By:	/s/ Anthony Marucci
	Name:	Anthony Marucci
	Title:	President and Chief Executive Officer

-3-