Emergent Biosolutions' typhoid vaccine achieves positive results in Phase II clinical study

Aug 30 2005

Emergent BioSolutions today announced positive results from a Phase II clinical study evaluating a new simplified dosing regimen for the company's next generation single dose oral typhoid vaccine. The results of the study were published in the August edition of the Journal of Infectious Diseases.

The Phase II study, conducted under a company-sponsored IND led by Dr. Beth D. Kirkpatrick at the University of Vermont, evaluated the safety and immunogenicity of the vaccine in 32 healthy adult volunteers. The study demonstrated that utilization of a simpler more rapid dosing regimen did not affect the excellent safety profile or the magnitude of the immune response stimulated by the vaccine. Previously, a single dose of the oral typhoid vaccine was shown to be safe, well tolerated and highly immunogenic in human volunteers when using a lyophilised product suitable for commercialization. However in previous studies subjects were required to be pre-dosed with a bicarbonate buffer and the vaccine strain was reconstituted in bottled water prior to administration. The improved regimen tested in the Phase II study announced today is a more rapid, commercially attractive formulation in that it removes the requirement for pre-dosing with bicarbonate buffer and the vaccine is administered immediately following reconstitution in tap water.

In the current trial, 16 subjects received the vaccine using the old regimen and another 16 subjects received the vaccine using the improved rapid dosing schedule. In both groups the vaccine was well tolerated. All volunteers mounted an immune response to the vaccine after a single dose, demonstrated by measuring mucosal and systemic antibody responses. There was no significant difference in the magnitude of the response between the two groups. This important result demonstrates that the vaccine can prime both the mucosal immune system, the body's first line of defense, as well as the systemic immune system, when administered using the improved dosing regimen. This is essential for a successful single dose approach. Injected vaccines generally elicit a systemic response but a poor mucosal immune response.

Commenting on the results, investigator Dr. Beth Kirkpatrick said, "We think this oral, single dose freeze-dried vaccine, which was simple to administer, is showing great promise providing an excellent basis on which to advance further clinical development. A single oral-dose typhoid vaccine which is simple to administer would facilitate vaccination in all populations, including travelers to, and residents living in areas where typhoid fever is endemic or epidemic."

"These latest clinical results are very encouraging," said Dr. Steven Chatfield, Emergent's Chief Scientific Officer. "The fact that the vaccine was produced using a commercially viable manufacturing process coupled with a simple dosing regimen vaccine will greatly facilitate further clinical development leading to a Phase III program."

Emergent is planning to evaluate its oral typhoid vaccine further in Phase II studies in Vietnam with financial support from the Wellcome Trust prior to starting Phase III studies.

Emergent used its patented Signature Tagged Mutagenesis (STM) functional genomics technology -- which allows the development of safe live attenuated vaccines -- to develop this new vaccine. The results of this clinical study further validate the approach of using the oral typhoid vaccine to orally deliver other vaccine antigens for delivery to the immune system. The company has already developed a vaccine against a common form of traveler's diarrhea (ETEC), and a therapeutic vaccine to treat chronic Hepatitis B carriers based on this approach. Both vaccines have been evaluated in Phase I clinical trials and were shown to be safe and immunogenic. Other conditions that could be prevented, or treated, are also being investigated and include bacterial and viral diseases, allergies and cancer.