Celldex Announces Planned Transition of Chief Financial Officer

Celldex (NASDAQ:CLDX) announced today that Sam Martin, Senior Vice President and Chief Financial Officer, has informed the Company of his plans to retire in 2027. Mr. Martin has served as the Company’s Chief Financial Officer since 2017 and as a member of the Celldex finance team since April 2009. Celldex has initiated a search for a new Chief Financial Officer, and Mr. Martin will remain as the Company’s CFO through March of 2027, to support a smooth transition.

“We are grateful to Sam for his strong contributions over many years of service to Celldex and wish him the very best in his retirement,” said Anthony Marucci, Co-founder, President and Chief Executive Officer of Celldex. “Sam has played an important role in Celldex’s growth from an emerging early-stage R&D company to a late-stage leading immunology company, leading a very successful finance organization that will continue to support our work towards building a fully integrated commercial company.”

“I am proud of what we have accomplished at Celldex and honored to have worked with such a talented team,” said Sam Martin, Senior Vice President and Chief Financial Officer at Celldex. “With a robust pipeline in development, a continued focus on growing commercial capabilities and important data readouts from two Phase 3 barzolvolimab trials expected later this year, I am excited about the future of the company and confident that it is well positioned for success.”

About Celldex Celldex is pioneering new horizons in immunology to deliver life-changing therapies. We are relentless in our pursuit of novel antibody-based treatments that engage the human immune system and directly affect critical pathways to improve the lives of patients with allergic, inflammatory and autoimmune disorders. Visit www.celldex.com .

Forward Looking Statement This release contains "forward-looking statements" made pursuant to the safe harbor provisions of the Private Securities Litigation Reform Act of 1995. These statements are typically preceded by words such as "believes," "expects," "anticipates," "intends," "will," "may," "should," or similar expressions. These forward-looking statements reflect management's current knowledge, assumptions, judgment and expectations regarding future performance or events. Although management believes that the expectations reflected in such statements are reasonable, they give no assurance that such expectations will prove to be correct or that those goals will be achieved, and you should be aware that actual results could differ materially from those contained in the forward-looking statements. Forward-looking statements are subject to a number of risks and uncertainties, including, but not limited to, our ability to successfully complete research and further development and commercialization of Company drug candidates, including barzolvolimab (also referred to as CDX-0159) and CDX-622, in current or future indications; the uncertainties inherent in clinical testing and accruing patients for clinical trials; our limited experience in bringing programs through Phase 3 clinical trials; our ability to manage and successfully complete multiple clinical trials and the research and development efforts for our multiple products at varying stages of development; the availability, cost, delivery and quality of clinical materials produced by our own manufacturing facility or supplied by contract manufacturers, who may be our sole source of supply; the timing, cost and uncertainty of obtaining regulatory approvals; the failure of the market for the Company's programs to continue to develop; our ability to protect the Company's intellectual property; the loss of any executive officers or key personnel or consultants; competition; changes in the regulatory landscape or the imposition of regulations that affect the Company's products; our ability to continue to obtain capital to meet our long-term liquidity needs on acceptable terms, or at all, including the additional capital which will be necessary to complete the clinical trials that we have initiated or plan to initiate; and other factors listed under "Risk Factors" in our annual report on Form 10-K and quarterly reports on Form 10-Q.

All forward-looking statements are expressly qualified in their entirety by this cautionary notice. You are cautioned not to place undue reliance on any forward-looking statements, which speak only as of the date of this release. We have no obligation, and expressly disclaim any obligation, to update, revise or correct any of the forward-looking statements, whether as a result of new information, future events or otherwise.

Company Contact Sarah Cavanaugh Senior Vice President, Corporate Affairs & Administration (508) 864-8337 [email protected]

Elizabeth Higgins Executive Director, Investor Relations & Corporate Communications (857) 404-2088 [email protected]