Celldex Presents Results from Phase 1 Studies of CDX-1307 with GM-CSF

CDX-1307 well tolerated with good immune responses observed

NEEDHAM, MA, USA | October 31, 2008 | Celldex Therapeutics, Inc. (NASDAQ: CLDX) announced initial results from multi-center Phase 1 clinical trials of its cancer vaccine candidate, CDX-1307, combined with GM-CSF, at the International Society for the Biologic Therapy of Cancer (iSBTc) annual meeting in San Diego. These data provide the basis for the ongoing assessment of CDX-1307 combined with more potent adjuvants with data expected in the first half of 2009.

"These CDX-1307 data provide further support for the tolerability and immunogenicity of Celldex's novel Precision Targeted Immunotherapy Platform," said Thomas Davis, M.D., Chief Medical Officer of Celldex Therapeutics. "We believe that specific immunotherapy combinations will provide even more potent clinical effects and, based on the safety and immunogenicity seen in these dose escalation studies, Celldex is now evaluating CDX-1307 in combination with the experimental Toll-Like Receptor agonists that the Company recently accessed."

CDX-1307 is a dendritic cell targeted immunotherapy designed to focus the immune system against hCG Beta, which is frequently expressed in epithelial tumors and has been associated with poor prognosis. The Phase 1 studies are open-label, dose-escalating clinical trials in patients with incurable breast, bladder, pancreatic, or colorectal cancer, all tumors that can express hCG Beta. The studies evaluated the safety and immunogenicity of multiple dosing of CDX-1307 alone and in combination with GM-CSF at multiple dose levels. In one dose escalation scheme 25 patients have received CDX-1307 by local intradermal injection at up to 2.5mg, and in the other Phase 1 study 25 patients have received CDX-1307 systemically via intravenous injection at higher doses of up to 30 mg.

CDX-1307 has been well tolerated at all doses and via both routes of administration without any Dose Limiting Toxicity. The most frequent treatment related toxicities were mild flu-like symptoms and mild local reactions associated with the intradermal injections. The hCG Beta was shown to be localized in antigen presenting cells of the skin in post-treatment biopsies following intradermal administration of CDX-1307. Even in the absence of potent adjuvants, humoral immune responses were seen in approximately half of patients at the higher dose levels despite circulating hCG Beta antigen, with reduction or clearance of hCG Beta in some patients. Enhancement of CD8 T-cell responses after vaccination was also seen in some patients. Despite advanced disease in the majority of patients, 2 patients experienced stable disease for at least 6 months and a minor response was seen in a patient with pancreatic cancer.

Based on the safety and immunogenicity seen in the dose escalation studies, Celldex is now evaluating CDX-1307 in combination with the experimental Toll-Like Receptor (TLRs) agonists that the Company recently accessed (poly-ICLC, a TLR 3 agonist, and resiquimod, a TLR 7/8 agonist) and expects results by mid-2009. Celldex then expects to initiate a Phase 2 clinical trial of CDX-1307 in combination with selected TLR agonists in the second half of 2009.

"The CDX-1307 data define the feasibility and tolerability of Celldex's novel antibody-targeting platform for cancer vaccines, allowing the flexibility to add novel adjuvant combinations such TLR agonists. This will enable the Company to uniquely advance its broad immunotherapy portfolio across a range of disease indications," added Anthony S. Marucci, President and Chief Executive Officer of Celldex Therapeutics, Inc.

About the CDX-1307 Vaccine

The Company has developed an APC Targeting Technology(TM) that utilizes fully human monoclonal antibodies to directly target specialized types of immune system cells, known as antigen presenting cells. The Company is advancing several clinical and preclinical product candidates that use APC Targeting Technology(TM) to manipulate critical types of antigen presenting cells, known as dendritic cells and macrophages, which are key cells within the immune system. Because these cells are largely responsible for initiating the immune system's disease-fighting mechanisms, the Company believes that product candidates using its technology will create more potent immune responses than standard vaccination strategies.

The Company's lead APC Targeting Technology(TM) product candidate, CDX-1307, is in development for the treatment of epithelial tumors such as colorectal, pancreatic, bladder, ovarian and breast cancers. CDX-1307 targets the beta chain of human chorionic gonadotropin, known as hCG-Beta, which is an antigen often found in epithelial tumors. The presence of hCG-Beta in these cancers correlates with a poor clinical outcome, suggesting that this molecule may contribute to tumor growth. Normal adult tissues have minimal expression of hCG-Beta; therefore, targeted immune responses are not expected to generate significant side effects.

About Celldex Therapeutics, Inc.

Celldex Therapeutics is an integrated biopharmaceutical company that applies its comprehensive Precision Targeted Immunotherapy Platform to generate a pipeline of candidates to treat cancer and other difficult-to-treat diseases. Celldex's immunotherapy platform includes a complementary portfolio of monoclonal antibodies, antibody-targeted vaccines and immunomodulators to create novel disease-specific drug candidates. For more information, please visit http://www.celldextherapeutics.com.

SOURCE: Celldex Therapeutics, Inc.

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