Poster Presented on Study Design for Phase 2 Study of CDX-1307 in Bladder Cancer

CHICAGO, IL, USA | June 7, 2010 |  Celldex Therapeutics, Inc. (NASDAQ: CLDX – News) today announced the presentation of promising clinical data on CDX-011 in metastatic melanoma at the 46th Annual Meeting of the American Society of Clinical Oncology (ASCO) in Chicago, Illinois. The Phase 2 study has met its primary endpoint and the results support additional studies in this indication. CDX-011 is an antibody-drug conjugate (ADC) in Phase 2 development for the treatment of melanoma and advanced breast cancer. In addition, in a separate presentation today at ASCO, the Company presented the study design for its recently initiated Phase 2 trial of CDX-1307 in bladder cancer. CDX-1307 is an antibody-based cancer vaccine candidate and is being evaluated as a treatment for bladder cancer.

“Both CDX-011 and CDX-1307 have demonstrated tremendous potential for the treatment of the most difficult to treat cancers,” said Anthony Marucci, President and Chief Executive Officer of Celldex Therapeutics. “Further development is warranted for both candidates and we look forward to reporting additional clinical data in the near future.”

CDX-011 Phase 2 Melanoma Study Results

In the poster entitled Frequent Dosing and GPNMB Expression with CDX-011 (CRO11-vcMMAE), an Antibody-Drug Conjugate (ADC), in Patients with Advanced Melanoma, Celldex described updated results from the Phase 2 portion of the multicenter, open-label Phase 1/2 study of CDX-011 in patients with unresectable Stage III/IV melanoma. A total of 34 patients were enrolled in the Phase 2 expansion and the primary activity endpoint of overall response rate (ORR) in the cohort was achieved with an ORR of 15%. Median progression free survival (PFS) was 3.9 months. CDX-011 was found to be active in advanced melanoma patients in the study.

In the Phase 2 expansion study, CDX-011 was administered at the pre-defined maximum tolerated dose (MTD) once every three weeks. A more frequent dosing schedule at MTD was evaluated in two additional, parallel dose-escalation arms in which patients received CDX-011 weekly (n=15) or twice every three weeks (n=6). The response rate was observed to be 20% and 33%, respectively.

CDX-011 consists of the potent cellular toxin MMAE conjugated to a fully-human monoclonal antibody (CR011) to GPNMB. The destruction of GPNMB-expressing cells, or transmembrane glycoprotein NMB, a novel glycoprotein expressed in over 80% of melanomas, may be involved in growth delay and reduction of a tumor’s metastatic potential. CDX-011 is designed to be stable in the bloodstream but to release MMAE upon internalization in GPNMB-expressing tumor cells, resulting in a targeted cell-killing effect. 83% (33/40) of patients with tumor sample analyzed by immunohistochemistry to date were positive for GPNMB expression. Preliminary data suggest an increase in PFS in patients with high tumoral GPNMB expression. The subset of seven patients, whose tumors were found to express high amounts of GPNMB, and who were treated at the maximum tolerated doses across all dosing schedules, demonstrated a median PFS of 4.9 months. The development of rash, which may be associated with the presence of GPNMB in the skin correlated with greater PFS. The most frequent treatment-related adverse events included rash, fatigue, alopecia (hair loss), pruritus, diarrhea and neuropathy.

CDX-1307 Bladder Cancer Study Design

In the poster entitled A Randomized Phase II Study of a Novel Antigen-Presenting Cell-Targeted hCG-β Vaccine (the CDX-1307 Regimen) in Muscle-Invasive Bladder Cancer, Celldex describes the study design for its Phase 2 trial of CDX-1307 in bladder cancer initiated in May of 2010. Recently CDX-1307 successfully completed a Phase 1 study in epithelial cancer.

In the multi-center Phase 2 controlled trial, 60 chemotherapy-naive patients with newly diagnosed, non-metastatic, resectable, muscle invasive hCG-beta positive bladder cancer will be randomized to receive either a neoadjuvant gemcitabine/cisplatin chemotherapy (GC) or CDX-1307 in combination with GC, poly-ICLC (PIC) and resiquimod (R) (the CDX-1307 regimen). The CDX-1307 dual mechanism of action shows that cytotoxic T cell responses specific to hCG-beta can directly kill tumor cells and that humoral anti-hCG-beta responses may neutralize anti-hCG-beta activity.

About CDX-011

CDX-011 is an antibody-drug conjugate (ADC) that consists of a fully-human monoclonal antibody, CR011, linked to a potent cell-killing drug, monomethyl-auristatin E (MMAE). The ADC technology, comprised of MMAE and a stable linker system for attaching it to CR011, was licensed from Seattle Genetics, Inc. Following intravenous administration, CDX-011 targets and binds to GPNMB, a specific protein that is predominantly expressed in cancerous tumors, including melanoma, breast cancer and gliomas. Upon internalization into the targeted cell, CDX-011 is designed to release MMAE from CR011 to produce a cell-killing effect. CDX-011 has been shown to be safe and active, with observed objective responses, in two positive trials in breast cancer and advanced melanoma.

About CDX-1307

CDX-1307 is the first antibody-based cancer vaccine designed to induce robust immune responses against cells containing the beta chain of human chorionic gonadotropin (hCG-beta) which are found in several epithelial tumors. hCG-beta appears to directly facilitate cancer progression and has been shown to correlate with poor prognosis. CDX-1307 consists of a fully human monoclonal antibody with specificity for the mannose receptor on dendritic cells, genetically linked to the hCG-beta tumor antigen and combined with the adjuvants TLR-7/8 agonist (toll-like receptor) and Hiltonol™ (a TLR-3 agonist). It is in development for colorectal, pancreatic, bladder, ovarian and breast cancers. CDX-1307 is derived from Celldex’ APC Targeting Technology™ platform.

About Celldex Therapeutics, Inc.

Celldex Therapeutics is the first antibody-based combination immunotherapy company. Celldex has a pipeline of drug candidates in development for the treatment of cancer and other difficult-to-treat diseases based on its antibody focused Precision Targeted Immunotherapy Platform. The PTI Platform is a complementary portfolio of monoclonal antibodies, antibody-targeted vaccines and immunomodulators used in optimal combinations to create novel disease-specific drug candidates. For more information, please visit http://www.celldextherapeutics.com.

SOURCE: Celldex Therapeutics, Inc.