Interim Positive Results From Phase 2b Brain Cancer Study With Rindopepimut (PF-04948568 or CDX-110) Presented at 46th Annual ASCO Meeting

Celldex Therapeutics, Inc. (NASDAQ: CLDX) today announced that interim results from a Phase 2b study evaluating rindopepimut (formerly PF-04948568 or CDX-110) in newly-diagnosed glioblastoma multiforme (GBM) patients were presented at the 46th Annual Meeting of the American Society of Clinical Oncology (ASCO). Rindopepimut, an investigational immunotherapeutic vaccine that targets the tumor-specific molecule epidermal growth factor receptor variant III (EGFRvIII), was developed by Celldex Therapeutics and is licensed to Pfizer.

"We are pleased that interim data from ACT III is consistent with data generated from our two previous clinical studies with rindopepimut in GBM,” said Anthony Marucci, President and Chief Executive Officer of Celldex Therapeutics. "70 percent of ACT III patients were progression-free at 5.5 months after initiating treatment with rindopepimut, which corresponds to the 8.5 months seen in ACT II and ACTIVATE when measured from diagnosis and surgery. The earlier ACTIVATE and ACT II trials reported progression free rates at 8.5 months of 70 and 80 percent, respectively. Importantly, previous studies were conducted in just a few leading centers, whereas ACT III enrolled patients in over 25 centers in the United States. We look forward to the final ACT III data later this year, and are working with Pfizer to determine appropriate next steps in the development of rindopepimut.”

Approximately 10,000 patients are diagnosed with GBM annually in the United States, and it is estimated that the EGFRvIII mutation may be expressed in approximately 25 to 30 percent of the GBM population.^1,2 Based upon historic controls from Duke/MDACC, median progression free survival for patients with EGFRvIII positive GBM is 6.3 months.

ACT III Results

-- For the planned interim analysis, 40 patients out of a total 65 were evaluated at 5.5 months for Progression Free Rate (PFR), a primary endpoint.

-- Patients were newly-diagnosed with EGFRvIII-positive GBM and had undergone successful surgery to remove the tumor. All patients received rindopepimut in combination with maintenance temozolomide (TMZ) after successful completion of standard radiation therapy and concurrent TMZ.

-- 5.5 month progression free rate (PFR) of 70 percent (28/40) while on treatment with rindopepimut is consistent with data observed in previous rindopepimut clinical studies in GBM. (The 5.5 month primary endpoint correlates with approximately 8.5 months since diagnosis/surgery.)

-- Adverse events as a result of treatment with rindopepimut were limited to injection site reactions and reversible hypersensitivity reactions. One hypersensitivity reaction was reported as a serious adverse event and required discontinuation of rindopepimut.

Study Design

The ongoing ACT III Phase 2 trial is a single-arm study that has enrolled 65 patients with newly-diagnosed EGFRvIII-positive GBM who have undergone surgical (gross total) resection followed by conformal radiation therapy and concurrent oral TMZ (75 mg/m2 per day) without tumor progression. Rindopepimut mixed with granulocyte-macrophage colony stimulating factor (GM-CSF) (142mcg) was administered intradermally. Patients received rindopepimut bi-weekly for three doses prior to starting maintenance TMZ and monthly thereafter until disease progression. The primary endpoint of the interim analysis was PFR at 5.5 months from first vaccination.

The ACT III Phase 2b trial originally included a control arm but was amended to a single arm design when 14/16 control arm patients declined further participation after notification of randomization assignment. When the patients randomized to the control arm withdrew from the study, the trial could no longer achieve the planned statistical goals.

About Pfizer Oncology

Pfizer Oncology is committed to the discovery, investigation and development of innovative treatment options to improve the outlook for cancer patients worldwide. Our strong pipeline, one of the most robust in the industry, is studied with precise focus on identifying and translating the best scientific breakthroughs into clinical application for patients across a wide range of cancers, including breast, lung, prostate, sarcoma, melanoma, and various hematologic cancers. Pfizer Oncology has more than 20 biologics and small molecules in clinical development and more than 100 clinical trials underway.

By working collaboratively with academic institutions, individual researchers, cooperative research groups, governments, and licensing partners, Pfizer Oncology strives to cure or control cancer with breakthrough medicines, to deliver the right drug for each patient at the right time. For more information please visit www.Pfizer.com.

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.

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 (PF-04948568 or CDX-110), CDX-1307, CDX-011, CDX-1135 (formerly TP10), CDX-1401, CDX-1127, 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 obtain additional capital on acceptable terms, or at all; our ability to adapt APC Targeting TechnologyTM 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; our development partners’ willingness to make announcements with respect to co-developed products; the uncertainties inherent in clinical testing; our ability to manage research and development efforts for multiple products at varying stages of development; Pfizer’s and our strategy and business plans concerning the continued development and commercialization of RINDOPEPIMUT (PF-04948568 OR CDX-110) ; 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; our ability to successfully integrate the businesses, multiple technologies and programs of CuraGen and Celldex; competition; changes in the regulatory landscape or the imposition of regulations that affect the Company’s products; and other factors listed in our annual report on Form 10-K for the fiscal year ended December 31, 2009, and its Forms 10-Q and 8-K.

¹ Heimberger, A.B., et al., "Prognostic effect of epidermal growth factor receptor and EGFRvIII in glioblastoma multiforme patients.” Clin Cancer Res, 2005. 11(4): p. 1462-6.

² Pelloski, C.E., et al., "Epidermal growth factor receptor variant III status defines clinically distinct subtypes of glioblastoma.” J Clin Oncol, 2007. 25(16): p. 2288-94.