PRESS RELEASE: Acambis Joins Forces With Sanofi Pasteur to Develop West Nile Virus Vaccine

Acambis Joins Forces With Sanofi Pasteur to Develop West Nile Virus Vaccine

CAMBRIDGE, England and CAMBRIDGE, Massachusetts, November 1 - No Human Vaccine Currently Exists Against the West Nile Virus, Which has Caused 3,265 Cases and 92 Deaths in the US so far in 2007; Collaboration Aims to Bring Leading West Nile Virus Vaccine Candidate to Market as Rapidly as Possible

Acambis plc (Acambis) , a leading vaccine development company, announced today that it has signed an exclusive global collaboration agreement with Sanofi Pasteur, the vaccines division of sanofi-aventis Group, for the development and marketing of Acambis' ChimeriVax(TM)-West Nile vaccine, which is the leading West Nile vaccine in development.
"Since 1999 when it was first detected in the US, the West Nile virus has spread across the entire continental United States, causing 27,240 cases and 1,054 deaths," commented Ian Garland, Chief Executive Officer of Acambis. "Vaccination is the ideal approach to tackling this disease and, through this unique collaboration, we aim to bring this vaccine to market as rapidly as possible."

"Providing a vaccine against West Nile disease may now be within reach. This vaccine candidate is the most promising in the industry and would help meet a growing public health need," said Wayne Pisano, President and Chief Executive Officer of Sanofi Pasteur.

Acambis started developing a West Nile vaccine in 1999, shortly after the virus was first identified in the US. Under the terms of the agreement, Acambis will continue to perform ChimeriVax(TM)-West Nile development activities, up to and including the filing of a license application in the US.

Acambis will receive an upfront payment of $10m in 2007 from Sanofi Pasteur, and would be eligible for pre- and post-marketing milestone payments of up to $70m based on product approval and sales in the US market. It would also be entitled to receive development funding and royalties on net sales of the vaccine. In addition, if the vaccine were registered in other countries, Acambis would be entitled to further post-marketing milestone payments and royalties.
There is currently no human vaccine for the prevention of West Nile virus-related disease and no specific treatment. As of 6 November 2007, 3,265 cases of disease and 92 deaths had been recorded in 42 US States by the US Centers for Disease Control and Prevention (CDC) this year. The CDC has identified those aged 50 and above as being most at risk of severe West Nile virus-related disease. In the US, this population totals more than 87 million people.

Acambis is currently conducting a Phase 2 safety, tolerability and immunogenicity trial of ChimeriVax-West Nile in the US in adults aged 41-64 years and 65 years and above. Preliminary data from a previous Phase 2 dose-ranging trial in healthy adults have shown that over 98% of subjects seroconverted 28 days after a single vaccination. The safety profile of the vaccine has been shown to be satisfactory. Acambis' West Nile vaccine candidate uses its proprietary ChimeriVax(TM) technology, which was developed in association with St Louis University.

About West Nile virus
West Nile virus is a potentially serious illness. Experts believe it is established as a seasonal epidemic in North America that flares up in the summer and continues into the fall. About one in 150 people infected with West Nile virus will develop severe illness. The severe symptoms can include high fever, headache, neck stiffness, stupor, disorientation, coma, tremors, convulsions, muscle weakness, vision loss, numbness and paralysis. These symptoms may last several weeks, and neurological effects may be permanent. Up to 20% of the people who become infected have symptoms such as fever, headache, body aches, nausea, vomiting, and sometimes swollen lymph glands or a skin rash on the chest, stomach and back. Symptoms can last for as short as a few days, though even healthy people have become sick for several weeks. Approximately 80% of people who are infected with West Nile virus will not show any symptoms at all.

About Acambis
Acambis is a leading vaccine company developing novel vaccines that address significant unmet medical needs or substantially improve standards of care. ChimeriVax(TM)-JE, Acambis' most advanced product in its non-biodefence pipeline, has to date shown an excellent safety and efficacy profile following pivotal Phase 3 trials. It is currently undergoing paediatric trials in India and is partnered with Sanofi Pasteur and Bharat Biotech. Acambis' proprietary ChimeriVax(TM) technology, developed in association with St Louis University, has also been used to develop ChimeriVax(TM)-West Nile, which is undergoing Phase 2 clinical testing, making it the most advanced investigational vaccine against the West Nile virus. Acambis has established a global collaboration with Sanofi Pasteur for further development and commercialization of the vaccine. ChimeriVax(TM) has also been applied to development of Sanofi Pasteur's tetravalent dengue vaccine, which has successfully demonstrated proof-of-concept in a Phase 2 trial by generating 100% seroconversion to all four dengue virus serotypes.

Acambis also has the only vaccine in development against Clostridium difficile bacteria, a leading cause of hospital-acquired infections. C. difficile is estimated to cause at least 350,000 cases of C. difficile-associated disease in the US alone with annual costs to the healthcare system of $1.1bn. Acambis' influenza program aims to develop a universal vaccine against influenza, for which a universal 'A' strain vaccine, ACAM-FLU-A, is currently being tested in a Phase 1 trial, and also includes various further vaccine candidates in the research and pre-clinical stages.

Acambis is recognised internationally as the leading producer of smallpox vaccines. Acambis' ACAM2000 (Smallpox (Vaccinia) Vaccine, Live) vaccine for active immunization against smallpox disease for persons determined to be at high risk for smallpox infection was licensed by the US Food and Drug Administration in August 2007. Acambis has manufactured doses of ACAM2000 for emergency-use stockpiles held by the US Government and several other governments around the world. For safety and prescribing information, please refer to http://www.acambis.com/ACAM2000 [1].
Acambis is based in Cambridge, UK and Cambridge, Massachusetts, US, and is listed on the London Stock Exchange (ACM). More information is available at http://www.acambis.com/ [2].

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Statements contained within this news release may contain forward-looking comments, which involve risks and uncertainties that may cause actual results to vary from those contained in the forward-looking statements. In some cases, you can identify such forward-looking statements by terminology such as 'may', 'will', 'could', 'forecasts', 'expects', 'plans', 'anticipates', 'believes', 'estimates', 'predicts', 'potential', or 'continue'. Predictions and forward-looking references in this news release are subject to the satisfactory progress of research which is, by its very nature, unpredictable. Forward projections reflect management's best estimates based on information available at the time of issue.