BioWorld International Correspondent
LONDON - Acambis plc said it has positive results from a Phase I/II trial of its Japanese Encephalitis (JE) vaccine, providing the first validation of its ChimeriVax platform technology for genetically engineered vaccines against diseases caused by flaviviruses. These include potential blockbuster vaccines against dengue fever and hepatitis C.
Chief Financial Officer Gordon Cameron told BioWorld International, "The results for JE validate the platform technology. This is the first time ChimeriVax has been tested in man. It has proven safe and efficacious, thereby increasing confidence for the other products using the same methodology."
ChimeriVax is derived from the live, attenuated 17D strain of the yellow fever virus, which is the basis for existing yellow fever vaccines. To create a ChimeriVax vaccine, the genes that encode the two proteins that confer immunity to yellow fever are replaced with the corresponding genes from the target flavivirus.
The randomized, double-blind Phase I/II trial in healthy volunteers showed the JE vaccine was safe, well tolerated and highly immunogenic after a single dose.
Because it is not possible to do a challenge trial, immunogenicity was accepted as proof of efficacy. "We will now conduct a larger-scale Phase IIb version of the trial to establish dose level in around 100 subjects," said Cameron. Acambis, based in Cambridge, UK, expects to start the trial later this year, and conclude it in 2002.
The JE vaccine is not partnered, and Cameron said the company, which changed its name from Peptide Therapeutics at the start of 2001, will wait until it has completed the next trial before looking for a partner. It sees two distinct markets for the product: as a pediatric vaccine in countries in Southeast Asia, where the disease is endemic, and as a travelers' vaccine.
"We will aim to find a partner for Asia and keep the rights in North America," Cameron said.
Vaccines against JE are available, and are used for universal immunization in Japan, Korea and Taiwan, but they require multiple doses and frequent boosters for protection. For this reason, the travelers' vaccine market is not developed.
Cameron said the validation of ChimeriVax would give Acambis "greater confidence to push its flavivirus programs in other diseases." The vaccine against dengue fever, a mosquito-borne virus affecting over 100 million people annually, is partnered with Aventis, and Cameron said the pharmaceutical company was "awaiting these results," before finalizing its development plans.
Last year Acambis was awarded a US$3 million grant from the U.S. National Institutes of Health to develop a ChimeriVax vaccine against West Nile encephalitis. The virus occurs in Europe, Africa and Asia, and was identified in the U.S. for the first time in 1999, when an outbreak in New York infected 62 people and killed seven.