Press Release

HAMPTON, N.J., Dec. 10, 2013 (GLOBE NEWSWIRE) -- Celldex Therapeutics, Inc. (Nasdaq:CLDX) announced today positive results from a preclinical combination study of CDX-301 (FMS-like tyrosine kinase-3 ligand or Flt3L) and Mozobil^® (Plerixafor injection, formerly AMD3100) demonstrating that the combination of these agents significantly increases hematopoietic stem cell mobilization in mice. The data support future clinical development of CDX-301 and demonstrate a novel potent cell mobilization regimen combining CDX-301 and Mozobil^®, which may have significant potential for use in autologous and allogeneic hematopoietic stem cell transplantation. Results were presented in an oral session entitled "FLT3L and AMD3100 Combination Increases Hematopoietic Stem Cell Mobilization and Leads to Improved Transplantation Outcome" on Tuesday, December 10, 2013 at 7:30 am CT at the American Society of Hematology 55^th Annual Meeting and Exposition (ASH). The studies were conducted in collaboration with Jianhua Yu, PhD, and Steven Devine, MD, and were presented by Shun He, PhD, all of The Ohio State University.

"We need novel interventions to advance hematopoietic stem cell mobilization techniques and transplantation, and based on our studies to date, this could be a promising alternative approach for these patients," said Steven Devine, MD, Professor of Internal Medicine and Director, Blood and Marrow Transplant Program, The Ohio State University Comprehensive Cancer Center.

"The data presented today further demonstrate the potential for CDX-301 to improve both autologous and allogeneic hematopoietic stem cell transplantation and, importantly, show the ability for CDX-301 to combine effectively with other cell mobilization agents," said Tibor Keler, PhD, Senior Vice President and Chief Scientific Officer of Celldex. "If what has been demonstrated in preclinical models can be applied to a clinical setting, this regimen could improve stem cell transplantation outcomes for patients across a broad range of indications. We plan to initiate a pilot clinical study evaluating CDX-301 alone and in combination with Mozobil^® in the transplant setting in early 2014 and look forward to seeing how this program progresses."

Current standard of care mobilization treatments produce grafts, or transplanted tissues, that may not contain sufficient numbers of hematopoietic stem cells or may cause graft-versus-host disease (GVHD), a common complication following allogeneic transplantation in which the immune cells in the graft recognize the host, or recipient, as foreign and react by attacking the host's cells. This study found that the combination of CDX-301 and Mozobil^® mobilized the highest rate and amount of hematopoietic stem cells into peripheral blood compared to the mice treated with granulocyte colony-stimulating factor (G-CSF, an FDA-approved mobilization treatment) alone, or the combination of G-CSF with Mozobil^®. In a model of autologous stem cell transplantation, there was greater than 70% survival among mice exposed to an otherwise lethal dose of radiation that had received grafts mobilized with the combination of CDX-301 and Mozobil^® or CDX-301 alone, whereas survival was only 35% when grafts were mobilized by G-CSF combined with Mozobil^®, and there was no survival with either G-CSF or Mozobil^® alone. Further, in a mouse model of allogeneic stem cell transplantation, the combination of CDX-301 with Mozobil^® or CDX-301 alone again resulted in significantly greater survival at four months (80% and 66%, respectively) than did the combination of G-CSF with Mozobil^® (13%) or did either agent alone (0%). The better outcomes from the CDX-301 alone or in combination with Mozobil^® appeared to be due to suppression of GVHD and also better hematopoietic reconstitution of stem cells.

Mozobil® is a registered trademark of Genzyme Corporation.

About CDX-301

CDX-301 or Flt3L is a potent hematopoietic cytokine currently in Phase 1 development that stimulates the expansion and differentiation of hematopoietic progenitor and stem cells. Flt3L has demonstrated a unique capacity to increase the number of circulating dendritic cells in both laboratory and clinical studies. In addition, Flt3L has shown impressive results in models of cancer, infectious diseases and inflammatory/autoimmune diseases. Celldex believes this ligand may hold significant opportunity for synergistic development in combination with other proprietary molecules in the Company's portfolio.

About Celldex Therapeutics, Inc.

Celldex is developing targeted therapeutics to address devastating diseases for which available treatments are inadequate. Our pipeline is built from a proprietary portfolio of antibodies and immunomodulators used alone and in strategic combinations to create novel, disease-specific therapies that induce, enhance or suppress the body's immune response. Visit www.celldex.com.

Safe Harbor Statement Under the Private Securities Litigation Reform Act of 1995:

This release contains "forward-looking statements" made pursuant to the safe harbor provisions of the Private Securities Litigation Reform Act of 1995, including those related to the Company's strategic focus and the future development and commercialization (by Celldex and others) of rindopepimut (CDX-110), glembatumumab vedotin ("glemba"; CDX-011), CDX-1135, CDX-1401, CDX-1127, CDX-301, Belinostat and other products. 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 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 rindopepimut, glembatumumab vedotin and other drug candidates, our ability to obtain additional 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; our ability to adapt our APC Targeting Technology^TM to develop new, safe and effective vaccines against oncology and infectious disease indications; our ability to successfully complete product research and further development of our programs; the uncertainties inherent in clinical testing; our limited experience in bringing programs through Phase 3 clinical trials; our ability to manage research and development efforts for multiple products at varying stages of development; 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; and other factors listed under "Risk Factors" in our annual report on Form 10-K.

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.

CONTACT: Sarah Cavanaugh

         Vice President of Investor Relations &

         Corp CommunicationsCelldex Therapeutics, Inc.

         (781) 433-3161

         scavanaugh@celldex.com

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