The company has secured a source of influenza antigen, allowing it to push forward with plans for Phase I clinical trials of the flu vaccine based on the firm's innovative GelVac dry powder technology.

This will be the first powder-based nasal flu vaccine to be used in a human trial, the company claims, although a liquid flu vaccine formulation, MedImmune's Flumist, has been on the market since 2003 and was the first needle-free flu jab to be launched.

Despite the availability if Flumist there seems to be room in the market for another non-injectable candidate. Medimmune's product has failed to make significant inroads into the injectable seasonal flu vaccine market and remains unprofitable, according to analyst comments regarding a proposed $15bn acquisition of the firm by AstraZeneca.

The GelVac powder is based on DelSite's GelSite natural carbohydrate polymer product. When the powder comes into contact with nasal fluids it forms a wet, mucoadhesive gel that entraps the vaccine antigen. According to the company, this provides a mechanism for prolonged exposure of the antigen to the nasal lymphoid tissue, potentially enhancing the protective immune response.

The vaccine itself boasts several attractive features that could make it particularly appealing as an option to meets the needs for pandemic preparedness and epidemic control, according to DelSite.

For example, the vaccine is stable at room temperature and therefore doesn't require freezing or cold chain distribution systems, making it a viable option in developing as well as developed countries.

The vaccine also has a prolonged shelf-life, having successfully been stored at room temperature for over two years, which is another point in its favour as a candidate for pandemic stockpiling.

The vaccine itself is also manufactured without the need for any organic solvents and uses no preservatives.

As well as this, the powder vaccine can be administered intranasally without the need for needles, making it perhaps more consumer friendly, but the product can also be reconstituted with sterile water and delivered via a standard injection, thus offering a choice of delivery method.

According to DelSite, the vaccine also boasts therapeutic advantages that make it a superior choice compared to standard vaccines. As a nasal vaccination, the GelVac system provides both local mucosal immunity in the nasal passage as well as system protection throughout the body. Injectable vaccination, on the other hand, tends to only induce a systemic immune response.

This double-immunity feature and the speed with which the nasal passage become protected could prove particularly useful when immunising children and the elderly who may have immature or weakened immune systems.

On top of this, the company asserts that its intranasal vaccination could also confer protection at other mucosal sites, such as the lungs or intestines, and provide cross-protection against variant strains though lymphocyte trafficking within the body.

GelVac is currently being developed to provide a vaccine to protect humans against the H5N1 avian flu virus, but has been designed to provide controlled release of a variety of peptide- and protein-based drugs and vaccines.

Formulations can be adjusted by varying the polymer concentrations, formulation parameters, and through the addition of selected adjuvants. Being a water-based system, GelVac is also suitable for a variety of antigen types, and the company also hopes that this nasal delivery platform could be suitable for delivering live attenuated viruses, live vectors and DNA vaccines.

The company has been encouraged by the positive results reported regarding FluMist's enhanced efficacy when compared to standard injected vaccines.

While this could help encourage the broader uptake of nasal vaccines in general, DelSite's product already has several plus points over FluMist, which despite being on the market several years had suffered poor sales due to impractical storage requirements that were only resolved with a new formulation approved earlier this year.

DelSite completed pre-investigational new drug (IND) talks with the US Food and Drug Administration (FDA) covering its nasal powder vaccine in November last year, and anticipates the IND application to be filed in late 2007 for clinical trials in the US.