pSivida Limited Reports Positive Phase IIa Trial Results in Liver Cancer; BrachySil Trial Confirms Safety and Tumor Regression in Further Patients

PERTH, Australia--(BUSINESS WIRE)--Feb. 14, 2005--Global nanotechnology company pSivida Limited (NASDAQ:PSDV, ASX:PSD, Xetra:PSI) today announced that its trial in inoperable primary liver cancer patients continues to show excellent results. Data from the second patient cohort of the current Phase IIa trial has further demonstrated that BrachySil(TM) (32-P BioSilicon(TM)) is safe and effective in tumor regression with increased efficacy.

Results of the second group of four patients, 12 weeks after their BrachySil(TM) treatment, revealed an average tumor regression by volume of 80% as determined by CT scanning. In some smaller tumors 100% regression was observed, a level of performance not seen with other intratumoral approaches. The study also demonstrated that there were no product-related adverse effects. Patients will continue to be monitored for six months post treatment.

These excellent results follow the announcement in October 2004 of the interim results from the first four patients, which also showed no product-related adverse effects and reported up to 60% regression of tumors.

BrachySil(TM) is a micron-sized particle in which the isotope 32-phosphorus is immobilized. pSivida believes that this product is unique in that it demonstrates a very high degree of isotope retention, thus reducing the risk of soluble radioactive material affecting healthy hepatic tissue, or entering the circulation and causing systemic toxicity.

pSivida's Managing Director, Mr. Gavin Rezos, said, "This further human evaluation of BioSilicon(TM) has met our expectations in terms of safety and the performance of the fine gauge needle injection procedure. We are also very pleased with the significant level of tumor regression achieved given the low dose being administered. Proof of the ability of BrachySil(TM) to retain radioactivity at the injection site is another significant outcome of the trial."

Other treatments for primary liver cancer include a variety of embolization and radio frequency ablation techniques. pSivida believes that BrachySil(TM) potentially offers the interventional radiologist a more versatile and safer product for the treatment of such tumors. The procedure is undertaken without surgery under local anesthetic and patients can be discharged the following day.

pSivida currently plans to pursue a 'device-based' regulatory approval route for BrachySil(TM), which could result in a much shorter development and registration timeframe than that commonly associated with a drug-based approval.

Following the completion of analysis of the final Phase IIa trial results, pSivida expects to begin a dose profiling study during 2005. pSivida then intends to commence multi-center pivotal registration trials during 2005 involving patients in Asia, Europe and the U.S. The objective of these trials is to obtain data to support registration of BrachySil(TM) as an approved treatment for primary liver cancer.

pSivida plans to expand the use of BrachySil(TM) as a treatment for a wider range of solid tumor indications. A Phase IIa clinical trial is scheduled to commence for a second cancer indication within the next year.

The brachytherapy market is currently over $600 million (US) per annum and is expected to exceed $1 billion (US) within the next few years (Bio-Tech Systems). BrachySil(TM) has the potential to significantly expand the current market size through its application to other cancers.

    The study has established four key findings:

    --  SAFETY - No product related adverse events
        Unlike other liver brachytherapy approaches that involve
        delivery via the hepatic artery and, in some cases, result in
        radioactivity affecting healthy tissue, BrachySil(TM) is
        administered directly into tumors restricting radioactivity to
        the tumor itself.

    --  EFFICACY - Treated tumors demonstrate significant tumor
        regression
        Implantation of tumors with BrachySil(TM) has resulted in
        tumoricidal activity around the implantation site. Although
        the primary objective of the study was to determine the safety
        profile of BrachySil(TM), CT scan analysis of tumors at the
        time of treatment and three months later demonstrates
        significant tumor regression in targeted lesions with a
        maximum regression of 100% from the dose used in the trial.

    --  SPECIFICITY - Retention of radioactivity in the tumor
        A key finding is that the radioactive 32P-BioSilicon(TM)
        nanostructured microparticles remain in the tumor with no or
        insignificant detectable radioactive leakage.

    --  EASE OF APPLICATION - Practical and rapid treatment of tumors
        with ultrasound and CT guidance
        The procedure has been shown to be straightforward and
        accurate for the treatment of tumors. From a market
        perspective, this demonstration is in line with the company's
        strategy to develop a simple procedure for the interventional
        radiologist to selectively treat specific tumors. A multi
        injector is in design phase to treat larger tumors with
        multiple implantations from a single entry.


    NOTES ON BRACHYSIL AND COMPETITIVE ADVANTAGES IN BRACHYTHERAPY

    1. BrachySil(TM) is being manufactured to worldwide regulatory
    guidelines by supply chain contract partners including HighForce,
    Micron Group, Atomizing Systems and AEA Technology QSA subsidiary
    Auriga Medical, a leading global producer and supplier of
    radioisotopes for healthcare.

    2. Brachytherapy treatment utilizing BioSilicon(TM) includes the
    following significant potential advantages:

    --  Short range - 32-P isotope has a short active range resulting
        in less damage to healthy tissue.
    --  Immobilization - 32-P device is immobilized in the tumor,
        significantly reducing risk of leakage or systemic side
        effects.
    --  Ease of application - BrachySil(TM) is delivered under local
        anesthetic and patients can be discharged the next day.
    --  Direct delivery - BrachySil(TM) is delivered via fine gauge
        needle, minimizing side effects and tissue trauma without the
        need for shielded rooms or robotic injectors allowing
        treatment in hospitals without the need for investment in
        specialized facilities.
    --  Range of tumors - fine gauge needle delivery allows potential
        application to many solid tumors, unlike current brachytherapy
        products.
    --  Distribution - 32-P half-life of 14 days allows more
        convenient distribution to hospitals and application in the
        patient.
    --  Manufacture - BioSilicon(TM) is radiation hard, allowing ease
        of manufacture of BrachySil(TM) from phosphorous-doped silicon
        used in the electronics industry without the need to build
        costly manufacturing facilities.

About pSivida Limited

pSivida is a global nanotechnology company committed to the biomedical sector and the development of products in healthcare. The company's focus is the development and commercialization of a modified form of silicon (porosified or nano-structured silicon) known as BioSilicon(TM). As a new and exciting biocompatible material, BioSilicon(TM) offers multiple potential applications across the high growth healthcare sector, including controlled release drug delivery, targeted cancer therapies (including brachytherapy and localized chemotherapy), tissue engineering and orthopedics. Potential diagnostics applications are being developed through its subsidiary AION Diagnostics Limited. More information is available at www.psivida.com.

This document contains forward-looking statements that involve risks and uncertainties. Although the company believes that the expectations reflected in such forward-looking statements are reasonable at this time, it gives no assurance that such expectations will prove to be correct. Given these uncertainties, readers are cautioned not to place undue reliance on such forward-looking statements. Actual results could differ materially from those anticipated in these forward-looking statements due to many important factors including: the company's failure to develop applications for BioSilicon(TM) due to regulatory, scientific or other issues. Other reasons are contained in cautionary statements in the Registration Statement on Form 20-F filed with the U.S. Securities & Exchange Commission, including, without limitation, under Item 3.D., "Risk Factors" therein. The company does not undertake to update any oral or written forward-looking statements that may be made by or on behalf of pSivida.