Celldex Therapeutics, Inc. Receives Fast-Track Designation for CDX-110, a Novel EGFRvIII Vaccine for Glioblastoma

Celldex Therapeutics, Inc. Receives Fast-Track Designation for CDX-110, a Novel EGFRvIII Vaccine for Glioblastoma

PHILLIPSBURG, N.J., Jan. 7 -- Celldex Therapeutics announced today that the U.S. Food and Drug Administration (FDA) has granted Fast Track designation to Celldex's CDX-110 for the treatment of EGFRvIII expressing Glioblastoma Multiforme (GBM). GBM is the most common and aggressive form of primary brain cancer and carries a very poor prognosis with current therapy. CDX-110 is an immunotherapy that targets the tumor-specific growth promoter EGFRvIII that can be expressed by GBM.

In the ACTIVATE Phase 2a study, GBM patients treated with CDX-110 showed a median survival time of 30 months, more than a 100 percent increase in survival, versus the historical control's median of 14.5 months. The study has demonstrated a median time-to-progression of 13 months (p=0.0001) versus the historical control's median of 6.4 months. GBM that recurred after treatment with CDX-110 consistently lost EGFRvIII expression with its aggressive growth signal. An extension study, ACT II, which combines CDX-110 with chemotherapy in a similar patient population, has not yet reached median time-to-progression or survival. Preliminary progression free survival (PFS) and overall survival (OS) data in ACT II look very similar to the ACTIVATE experience, and the data suggest that chemotherapy and CDX-110 can be administered concurrently while still maintaining strong immune responses.

In September, Celldex randomized its first patient into ACT III, a definitive Phase 2/3 randomized study of CDX-110 with radiation and temozolomide in patients with newly-diagnosed GBM. The clinical trial is investigating the anticancer activity, impact on survival, and safety of the addition of CDX-110 vaccine to standard of care, versus standard of care alone. Celldex recently announced that CDX-110 has also been granted Orphan Drug Status by the FDA. Celldex Therapeutics announced a definitive merger agreement with AVANT Immunotherapeutics, Inc. in October 2007.

"Fast Track status acknowledges CDX-110's potential to fill an unmet need for glioblastoma patients and gives it priority within the FDA," said Thomas Davis, M.D., Chief Medical Officer of Celldex Therapeutics. "Confirmation of the promising results we've already observed is a high priority at Celldex, as it is within the brain cancer community in general."

About CDX-110

CDX-110 is an investigational immunotherapy that targets the tumor specific molecule EGFRvIII, a functional variant of the epidermal growth factor receptor (EGFR), which is a protein that has been well validated as a target for cancer therapy. This particular variant, EGFRvIII occurs in about 40 percent of Glioblastoma Multiforme (GBM) patients. It was discovered in a collaborative effort between Dr. Bert Vogelstein and Dr Albert Wong at Johns Hopkins University and Dr. Darell Bigner at Duke University. Unlike EGFR, EGFRvIII is not present in normal tissues, suggesting this target will enable the development of a tumor-specific therapy for cancer patients. Furthermore, EGFRvIII is a transforming oncogene that can directly contribute to cancer cell growth. While originally discovered in GBM, the most common and aggressive form of brain cancer, the expression of EGFRvIII has also been observed in various other cancers such as breast, ovarian, metastatic prostate, colorectal, and head & neck cancers. Celldex has exclusive rights to EGFRvIII vaccines and is pursuing the development of CDX-110 for GBM therapy, as well as in other cancers through additional clinical studies.

About Fast Track Drug Designation

Under the FDA Modernization Act of 1997, designation as a Fast Track product for a new drug or biological products means that FDA will take such actions as are appropriate to expedite the development and review of the application for approval of such product. FDA may also evaluate for filing and commence review of portions of an application for approval of a Fast Track product under certain conditions.

About Celldex Therapeutics, Inc.

Celldex Therapeutics, Inc. is a biotechnology company focused on developing therapeutic vaccines that target and stimulate the body's immune system for the treatment of cancer, infectious and autoimmune diseases. Celldex has three product candidates already in or about to enter clinical development targeting multiple cancers and Hepatitis B. Four additional product candidates are in preclinical development for cancer and autoimmune disease. Celldex's proprietary technology platform uses fully human monoclonal antibodies administered directly to patients to target and stimulate dendritic cells - key cells within the immune system. The Company is headquartered in Phillipsburg, New Jersey. On October 22, 2007, Celldex and AVANT Immunotherapeutics, Inc. announced that they had signed a definitive merger agreement. The all-stock transaction, approved by both companies' Boards of Directors, will combine Celldex and AVANT. Closing of the merger is contingent upon a vote of approval by the current stockholders of AVANT at a special meeting expected to take place in the first quarter 2008. For more information, please visit the website: http://www.celldextherapeutics.com.

Additional Information about the Merger and Where to Find It This communication contains "forward-looking" statements within the meaning 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 are subject to risks and uncertainties that may cause actual future experience and results to differ materially from those discussed in these forward-looking statements. Important factors that might cause such a difference include, but are not limited to, costs related to the Merger, failure of AVANT's stockholders to approve the Merger; AVANT's or Celldex's inability to satisfy the conditions of the Merger; AVANT's inability to maintain its NASDAQ listing; the risk that AVANT's and Celldex's businesses will not be integrated successfully; the combined company's inability to further identify, develop and achieve commercial success for new products and technologies; the possibility of delays in the research and development necessary to select drug development candidates and delays in clinical trials; the risk that clinical trials may not result in marketable products; the risk that the combined company may be unable to successfully secure regulatory approval of and market its drug candidates; the risks associated with reliance on outside financing to meet capital requirements; risks associated with Celldex's new and uncertain technology; risks of the development of competing technologies; risks related to the combined company's ability to protect its proprietary technologies; risks related to patent-infringement claims; risks of new, changing and competitive technologies and regulations in the U.S. and internationally; and other events and factors disclosed previously and from time to time in AVANT's filings with the Securities and Exchange Commission, including AVANT's Annual Report on Form 10-K for the year ended December 31, 2006. The companies do not undertake any obligation to release publicly any revisions to such forward-looking statements to reflect events or circumstances after the date hereof or to reflect the occurrence of unanticipated events.

This communication may be deemed to be solicitation material in respect of the proposed merger of AVANT and Celldex. In connection with the proposed merger, AVANT and Celldex intend to file relevant materials with the SEC, including AVANT's joint registration statement/proxy statement on Form S-4. SHAREHOLDERS OF AVANT ARE URGED TO READ ALL RELEVANT DOCUMENTS FILED WITH THE SEC, INCLUDING AVANT'S PROXY STATEMENT, BECAUSE THEY WILL CONTAIN IMPORTANT INFORMATION ABOUT THE PROPOSED TRANSACTION. Investors and security holders will be able to obtain the documents free of charge at the SEC's web site, http://www.sec.gov, and AVANT shareholders will receive information at an appropriate time on how to obtain transaction-related documents for free from AVANT. Such documents are not currently available.

Participants in the Solicitation

The directors and executive officers of AVANT and Celldex may be deemed to be participants in the solicitation of proxies from the holders of AVANT common stock in respect of the proposed transaction. Information about the directors and executive officers of AVANT is set forth in the proxy statement for AVANT's most recent 10-K, which was filed with the SEC on March 16, 2007. Investors may obtain additional information regarding the interest of AVANT and its directors and executive officers, and Celldex and its directors and executive officers in the proposed transaction by reading the proxy statement regarding the acquisition when it becomes available.