BioVex Limited has received a Notice of Allowance from the US Patent and Trademark Office in relation to one of its core patents. The patent relates to the use of HSV as a platform for antigen delivery for vaccine purposes and covers both direct in vivo and ex vivo applications of the technology. The patent specifically relates to modified versions of HSV that allow high efficiency antigen delivery to dendritic cells combined with dendritic cell activation.

Considerable evidence from advanced clinical trials has shown that antigen presentation by the immune systems key policing cells - dendritic cells -- can lead to a therapeutically effective immune response against disease associated antigens.

HSV infects and delivers antigen-encoding genes to dendritic cells at very high efficiency and has the potential to become the method of choice for antigen delivery to these cells. However, dendritic cells infected with HSV are usually in-activated by the infection process. BioVex has identified the HSV genes responsible for this inactivation. The deletion of these genes provides a proprietary vaccine platform which combines very efficient antigen delivery to, and optimal stimulation of, this key class of antigen presenting cell.

The Company's lead product from this platform, ImmunoVEX tri-melan is for the therapy of malignant melanoma. The product, which delivers three complete melanoma associated antigens to dendritic cells, is expected to enter a Phase I/II trial in the first quarter of 2004. The Company believes it is the only triple whole antigen vaccine being developed for the treatment of melanoma. In addition, the Company is developing a number of prophylactic ImmunoVEX vaccines for various infectious diseases including those caused by HSV2, HIV and HPV.