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Phase 2 Trial of Anthrax Vaccine Candidate Initiated

BRISBANE, Calif., April 15 /PRNewswire-FirstCall/ -- VaxGen, Inc. announced today that it has initiated a Phase II trial of its recombinant anthrax vaccine, rPA102. The 13-month trial is taking place at up to 12 medical centers in the United States and is one of two studies of rPA102 that VaxGen intends to initiate this year under a multi-year, $80.3 million U.S. government contract from the National Institute of Allergy and Infectious Diseases (NIAID), part of the National Institutes of Health.

"Given the urgent unmet need for a next-generation anthrax vaccine, VaxGen is particularly pleased to advance the clinical development of rPA102," said Lance K. Gordon, Ph.D., VaxGen's president and chief executive officer. "The ability to start a Phase II clinical trial of rPA102 within months of winning our latest anthrax contract from NIAID is a testament to VaxGen's ability to deliver results under tight deadlines and to satisfy the regulatory and contractual requirements of the program. We look forward to continuing what has been a very productive public-private sector collaboration."

The Phase II study will evaluate the safety and immunogenicity of different formulations of rPA102 among 480 healthy volunteers. Each formulation will contain varying concentrations of recombinant Protective Antigen (rPA) and aluminum hydroxide, an adjuvant designed to enhance the immune response. The goal of the study is to determine the optimal combination of rPA and the adjuvant required to induce the most robust immune response. rPA is a synthetic protein that induces antibodies that are designed to prevent illness by neutralizing anthrax toxins.

VaxGen plans to conduct a second Phase II trial of rPA102 later this year that will be designed to determine the optimal dosing schedule for the anthrax vaccine candidate, both for prevention and treatment of exposure to inhalation anthrax.

Based on the work of the U.S. Army Medical Research Institute of Infectious Diseases, rPA102 combines the potential safety benefits of a product made through modern recombinant technology with efficacy demonstrated in animal models. rPA102 cannot cause anthrax infection.

VaxGen began developing rPA102 to address the need for an anthrax vaccine that has an improved safety profile and a more practical dosing schedule compared to the existing licensed anthrax vaccine. The approved dosing regimen for the only currently licensed anthrax vaccine in the United States, AVA, requires six doses administered over an 18-month period.

VaxGen launched a Phase I trial of rPA102 in the second quarter of 2003 that compared the safety and immunogenicity of escalating doses of rPA102 to those of AVA. The results of the study, presented at the International Conference on Emerging Infectious Diseases (ICEID) in Atlanta on March 2nd, indicated that rPA102 elicited an immune response comparable to that of AVA, even though AVA contained more than 10 times the amount of adjuvant. The study also demonstrated a dose-response relationship in all rPA treatment groups. rPA102 was well-tolerated, with no significant safety or reactogenicity issues.

Source: VaxGen, Inc.

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