Recombinant Protective Antigen (rPA)

Avecia is developing this vaccine for the prevention of anthrax infection. It has completed Phase I trials and is in the final reporting stage of a Phase II trial. The vaccine has been shown to be well tolerated and induces an immune response in humans.

The vaccine is a recombinant Protective Antigen (rPA), absorbed on Alhydrogel. It was invented by Dstl (Defence Science & Technology Laboratory) part of the UK Ministry of Defence). Avecia’s role and technology expertise has been in developing the processes needed to move from laboratory scale to volume production and in progressing the product’s clinical development.

The Avecia route is a three-stage process, involving fermentation (using an E.coli expression system), downstream purification and formulation. The vaccine is designed to induce an immune response to protective antigen, which prevents the anthrax toxins from entering, disabling and killing cells and from interfering with certain aspects of the body’s immune system. Production of the protective antigen does not involve the anthrax germ itself, but is based on a highly purified and modified genetic sequence derived from it.

The drug substance for the vaccine is manufactured in Avecia’s facility in the Tees Valley, UK, and the drug product is manufactured by a leading contractor in the USA. The drug substance manufacturing process has recently been validated at full commercial scale and is capable of producing batches of up to one million doses.

To date there have been three sets of clinical trials: a Phase I trial to test safety and two Phase II trials to test safety, dose and schedule. The results show:

• the vaccine is well tolerated at all doses and schedules tested
• no safety differences were identified between male and female volunteers
• no vaccine related SAEs (Serious Adverse Effects) were seen

Avecia believes it has optimised the primary dose and schedule.