new discovery. announcement

ASX/MEDIA RELEASE 5 July 2006

New Discovery: BioSilicon TM Demonstrates Adjuvant Properties
Potential to be exploited in delivery of vaccines

Boston, MA. and Perth, Australia – Global bio-nanotech company pSivida Limited
(ASX:PSD, NASDAQ:PSDV, Xetra:PSI) is pleased to announce that its novel drug delivery platform, BioSiliconTM has demonstrated the capability to act as an adjuvant when delivered with an antigen. A patent application has been filed in the U.K. which covers the application of BioSiliconTM as an adjuvant.

• A vaccine is any substance bearing antigens (any substance capable of eliciting an immune response) on its surface that causes activation of a human’s or animals' immune system without causing actual disease.

• An adjuvant is any substance that is capable of enhancing a host response towards an active agent and is often used in conjunction with antigens to enhance the immune response of humans and animals.

Recent in vivo pre-clinical data demonstrate that BioSiliconTM alone does not stimulate the immune system. This finding is critical since it confirms the biocompatible attribute of this novel biodegradable biomaterial. The controlled study also demonstrated that certain forms of BioSiliconTM, delivered in specific combinations with a specific antigen, showed an adjuvant activity equivalent to the well established and widely used adjuvant, alum (aluminium salts).

The BioSiliconTM-antigen combinations resulted in an enhanced immune response based on in vivo antibody responses. This finding opens up the potential for exploiting BioSiliconTM not only for the delivery of vaccines, but also for enhancing the immune response to those vaccines. The global market for vaccines is estimated at $8 billion.

“This finding indicates the potential utility of BioSiliconTM in the vaccine delivery market,” said Mr Gavin Rezos, CEO of pSivida Limited. “The discovery of the adjuvant properties of BioSiliconTM presents an exciting new development and widens the potential market for this novel biodegradable biomaterial”.

-ENDS