Emergent BioSolutions moves forward with typhoid vaccine

The Maryland-based biopharmaceutical company is developing a single-dose oral drinkable typhoid vaccine aimed to take on Crucell's three to four dose oral formulation and Sanofi's injectable formulation. The global travellers market was worth $130m (€92m) in 2003, and is expected to increase to $200m by 2014. According to the company, the typhoid vaccine candidate achieved the study endpoints for safety and immunogenicity with an overall immune response rate of greater than 50 per cent, with 95 per cent confidence. "We are very pleased to have met the objective of this Phase II study of our typhoid vaccine candidate. This data is encouraging and indicates great promise for what would be the first single-dose, drinkable typhoid vaccine,"​ Emergent BioSolutions chairman and chief executive Fuad El-Hibri said. "Typhoid is endemic in many developing countries, putting countless international travellers and families who visit these nations at risk. With typhoid claiming 200,000 lives each year, continued progress in the development of this vaccine is an important milestone in our company's efforts to protect life." ​ The company's typhoid vaccine candidate is a live, attenuated strain of the Salmonella typhi​ bacterium designed to eliminate virulence by deletion of two specific genes. The vaccine is freeze-dried and reconstituted with water and administered orally prior to travel. Previous studies by the company have used a pre-dosing regimen using a bicarbonate buffer, but Emergent BioSolutions have looked at improving the dosing regimen to make it a more "commercially attractive formulation" and have since removed the requirement of pre-dosing. In this Phase II study, conducted in Vietnam, 101 children aged between five and 14 received the vaccine candidate and 50 children received a placebo. The vaccine was found to induce significantly higher antibody concentrations, indicative of systemic responses, in children in the vaccine group compared to the placebo control group. Previous studies have also shown the vaccine candidate to elicit a mucosal immune response as well as a systemic response. Injected vaccines tend to only produce systemic responses. According to a press release from the company: "If approved, this method of administration could provide a competitive advantage compared to currently approved typhoid vaccines."​ Currently, there are two vaccines against typhoid: Crucell's Vivotif, a three to four dose oral vaccine; and Sanofi​'s Typhim-Vi, a single-dose, injectable product. As yet there is no oral drinkable form of typhoid vaccine available. However, US-based Avant​ Immunotherapeutics started a Phase II study at the end of July on its typhoid fever​ vaccine candidate, Ty800. The aim is to develop a single-dose oral vaccine, which is freeze-dried and reconstituted with water, to be taken as a drink. Emergent BioSolutions spokeswoman Tracey Schmitt told in-PharmaTechnologist.com: "We are committed to serving under-met health needs and there is not currently a single dose drinkable typhoid vaccine on the market." ​ "Additionally, we believed this would be the best accepted form of vaccine from both a physician and patient perspective." ​ The Phase II study in Vietnam was the first study of this product candidate in a paediatric population in a region where typhoid is endemic. The study was performed in collaboration with Oxford University and Vietnam's Hospital for Tropical Diseases, and was financially supported by the Wellcome Trust. Phase III trials are expected to begin in 2009 with a safety study to be conducted in the US and EU and an efficacy study to take place in India.