Immediate Release: April 16, 2008

Immediate Release: April 16, 2008

PFIZER AND AVANT ENTER INTO LICENSING AND DEVELOPMENT AGREEMENT

FOR NOVEL THERAPEUTIC VACCINE CANDIDATE FOR BRAIN CANCER

YORK and NEEDHAM, MA (April 16, 2008) Pfizer, Inc. (NYSE: PFE) and

AVANT Immunotherapeutics (Nasdaq:

AVAN), acting through its wholly-owned subsidiary Celldex Therapeutics, Inc. today

announced that they have entered into an agreement under which Pfizer will be

granted an exclusive worldwide license to a therapeutic cancer vaccine

candidate, CDX-110, in Phase 2 development for the treatment of glioblastoma

multiforme (GBM). This agreement also gives Pfizer exclusive

rights to the use of EGFRvIII vaccines in other potential indications.

which has been granted both Fast Track and Orphan Drug designations by the U.S.

Food and Drug Administration (FDA), 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 in certain tumor types.

is only expressed in cancer cells and not in normal tissue and is a transforming

oncogene that can directly

to cancer cell growth, as it does in about 40 percent of GBM tumors.

are excited about the potential for CDX-110 and intend to partner with AVANT

and academic physician-scientists to investigate this novel vaccine candidate

with the hope of providing patients and doctors with a new treatment option for

this devastating disease, said Dr. Briggs Morrison, Senior Vice President

for Clinical Development at Pfizer.

the licensing and development agreement, Pfizer will make an upfront payment to

AVANT of $40 million and will make a $10 million equity investment in AVANT.

Pfizer will fund all development costs for these programs. AVANT is also

eligible to receive milestone payments exceeding $390 million for the

successful development and commercialization of CDX-110 and additional EGFRvIII

vaccine products, as well as double-digit royalties on any product sales.

The agreement is subject to approval under the Hart-Scott-Rodino Antitrust

Improvements Act of 1976 (as amended) and is expected to close in the second

advances the therapeutic potential for CDX-110, particularly for patients with

GBM. We are very pleased to initiate

this relationship to expand our clinical development activities for GBM and

toward other cancers, said Ron Newbold, Ph.D., Senior Vice President of Business Development

of AVANT Immunotherapeutics. Una Ryan,

CEO of AVANT, added, We see this as an important milestone for the immunotherapy

field, and we look forward to Pfizer s commitment to help even more cancer

patients in the future.

is designed to induce or enhance the body s immune responses against EGFRvIII

resulting in destruction of tumor cells that express the variant receptor. Early efficacy and

data from single arm Phase 2 clinical trials of CDX-110 in combination with the

current standard treatment for patients with GBM are very encouraging. Progression-free survival and overall

survival data from these trials compare very favorably with historical control

data. A randomized Phase 2 trial is

is the most common and aggressive form of primary brain tumor, with very poor

prognosis. There are an estimated 10,000

new cases of GBM annually in the United States, which predominantly affects

adults aged 45 to 70. The current standard treatment for patients with GBM

includes surgical resection, radiotherapy with concurrent temozolomide and then

adjuvant temozolomide chemotherapy.

AVANT Immunotherapeutics, Inc.

Immunotherapeutics and Celldex Therapeutics combined during the first quarter

of 2008. AVANT is a NASDAQ-listed

company discovering and developing innovative vaccines and targeted

immunotherapeutics for the treatment of cancer, infectious and inflammatory

diseases. AVANT focuses on the use of tumor-specific targets and human

monoclonal antibodies (mAbs) to precisely deliver therapeutic agents through

its novel targeted immunization approach. In addition, AVANT is exploiting

its access to proprietary human antibody technology for development of

therapeutic monoclonal antibodies (mAbs).

AVANT s deep product pipeline consists of products in varying stages of

development. Identification of the potential of EGFRvIII in

diagnosis, prevention and therapy was based on the collaborative efforts of Dr. Bert

Vogelstein and Dr. Albert Wong at Johns Hopkins University and Dr. Darell

Bigner at Duke University. Application

of this discovery toward the development of the CDX-110 vaccine was further

advanced by Dr. John Sampson and his colleagues at the Duke University

Brain Tumor Center in collaboration with Dr. Amy Heimberger at the MD

Anderson Cancer Center. AVANT also has

several product candidates in its development pipeline including:

a product based on its proprietary APC Targeting Technology , which

is in two Phase 1 clinical trials for patients with advanced pancreatic,

bladder, breast and colon cancer;

a complement inhibitor, in development for transplantation and other

candidates based on its oral, rapidly-protecting, single-dose and

temperature-stable vaccine technology, including combination vaccines for

travelers, the military and global health needs.

AVANT has three commercialized products, including Rotarix (partnered

with GSK) for the prevention of rotavirus infection and two human food safety

vaccines for reducing salmonella infection in chickens and eggs. Additional

information on AVANT Immunotherapeutics, Inc. can be obtained through its

web site http://www.avantimmune.com.

more information on Pfizer or AVANT please visit www.pfizer.com or

DISCLOSURE NOTICE: The information contained in this release is as of April 16,

2008. Pfizer assumes no obligation to update any forward-looking statements

contained in this release as the result of new information or future events or

release contains forward-looking information about a license agreement between

Pfizer Inc. and AVANT Immunotherapeutics relating to a therapeutic cancer

vaccine candidate, CDX-110, and other potential vaccines and the potential

benefits thereof. This information involves substantial risks and uncertainties

including, among other things, the satisfaction of the condition to closing the

agreement; the uncertainties inherent in research and development activities;

decisions by regulatory authorities regarding whether and when to approve any

drug applications that may be filed for CDX-110 and other potential vaccines as

well as their decisions regarding labeling and other matters that could affect