Acambis Commences First Human Clinical Trial of West Nile Vaccine

CAMBRIDGE, U.K. and CAMBRIDGE, Mass. -- Acambis, a leading developer of vaccines against infectious diseases, announces the start of a Phase I trial of its investigational vaccine against West Nile virus, ChimeriVax-West Nile.

Since it was first identified in New York in 1999, the West Nile virus has swept through 45 U.S. states, causing disease in more than 12,000 people and resulting in the deaths of several hundred individuals. In 2003 alone, it has affected more than 8,200 people and caused 182 deaths. The virus has also spread south to Central America and the Caribbean, and north into Canada where it has been identified in seven provinces.

Acambis used its proprietary ChimeriVax technology to develop the investigational ChimeriVax-West Nile vaccine and has conducted a series of successful pre-clinical studies on the vaccine. Acambis has now started a Phase I clinical trial in humans.

The trial is being conducted in Lenexa, Kan. under a Food and Drug Administration (FDA) Investigational New Drug application. The trial is a randomized, double-blind out-patient study in 60 healthy adult volunteers. It will test the safety, tolerability and immunogenicity of the ChimeriVax-West Nile vaccine.

The 60 volunteers will receive either a single vaccination with one of the three different dose levels of ChimeriVax-West Nile being tested or a licensed yellow fever vaccine that is being used as a control in the trial. Safety and tolerability will be judged by recording adverse reactions to the vaccine and immunogenicity will be measured in terms of antibody levels and T cell responses generated against West Nile virus.

"West Nile virus has become established as an endemic and epidemic disease that poses a significant threat to human health and a preventive vaccine could become a major factor in the fight against this virus," said Dr. John Brown, CEO of Acambis. "Acambis began work on this project within months of the virus being diagnosed in the US and we are pleased to be the first company to start human clinical trials to evaluate a vaccine against West Nile."

Acambis' work on ChimeriVax-West Nile has been partly financed by a $3 million grant from the U.S. National Institutes of Health, awarded to Acambis in August 2000.

West Nile virus was first identified in 1937 in the West Nile district of Uganda from which it takes its name. Since then, it has been seen in Africa, Europe, the Middle East, west and central Asia, Oceania and, most recently, North America. Recent human outbreaks have occurred in Algeria (1994), Romania (1996/7), Czech Republic (1997), the Democratic Republic of Congo (1998), Russia (1999), US (1999-2002) and Israel (2000). West Nile was first detected in New York in the summer of 1999. That year, the city experienced 62 cases of West Nile infection and seven people died. Although human cases of West Nile were found only in New York City during 1999, the virus was detected in animals and birds in the states of Connecticut, New Jersey, New York and Maryland. By the end of 2000, the virus had been found in a further nine states taking the total number of infected states to 13. That year, the virus caused severe infections in 18 people and for two of them it was fatal. During 2001, the virus spread through another 16 states, killing nine and causing severe illness in 66.

This year, the virus has had a greater impact than in any of the previous years. It has spread to a total of 45 U.S. states, and there have been more than 8,200 human infections and 182 deaths.

Source: Acambis plc