Cubist Pharmaceuticals and XTL Biopharmaceuticals Announce Completion of Independent Data and Safety Monitoring Board Review of Phase 2 Data for HepeX-B.

LEXINGTON, Mass. -- DSMB Recommends Continuation of Trial

Cubist Pharmaceuticals, Inc. (Nasdaq: CBST) and XTL Biopharmaceuticals Ltd. (LSE:XTL) today announced the completion of the first scheduled review by an independent data and safety monitoring board (DSMB) of the first group of 15 patients enrolled in the ongoing Phase 2 clinical trial. The trial is the second of two planned Phase 2 trials. This study is examining the safety and efficacy of HepeX-B(TM) (libivirumab and exbivirumab for injection) for prevention of hepatitis B reinfection in patients who have received liver transplantation for end-stage hepatitis B infection, and who have been maintained on hepatitis B immune globulin (HBIg).

The clinical protocol for an open-label study of HepeX-B(TM) was designed with input from the U.S. Food & Drug Administration (FDA) and specifies for periodic scheduled open-label reviews of the clinical data by an independent DSMB. Based upon a review of the data provided by XTL, the DSMB, convened by Duke Clinical Research Institute at Duke University, has recommended continuation of the trial. Patients are currently being enrolled in the trial in the U.S. and in Israel. Centers in several Western European countries will be opened shortly.

About HBV 

Hepatitis B is most commonly caused by the Hepatitis B virus, which, according to Datamonitor, has infected over 2 billion people around the world. Although a vaccine against HBV was introduced in 1982, globally, 350 million people are infected chronically with the disease and approximately 1 million people die each year as a result of complications from HBV infection. Current treatment regimens for chronic HBV often include use of interferon alpha or an antiviral drug. Despite these treatment options, chronic HBV can lead to severe liver damage and patients may require liver transplantation To prevent re-infection of the new liver with HBV, patients are currently treated with hepatitis B immune globulin (HBIg) combined with an antiviral compound, such as lamivudine. The global market for HBIg is estimated to be about $100 million annually.

About HepeX-B(TM)

HepeX-B(TM) is a combination of two fully human monoclonal antibodies, selected using XTLbio's pre-clinical Trimera(TM) model, that target HBV surface antigens. It is currently in an international Phase 2 study for the prevention of infection by HBV in liver transplant patients who have been maintained on HBIg. In clinical studies, HepeX-B(TM) maintained serum levels similar to or higher than the current first-line treatment, HBIg, using 1,000 times less drug. HepeX-B(TM) has already been granted Orphan Drug Status in both the U.S. and the European Union.

About Cubist

Cubist Pharmaceuticals, Inc. is a biopharmaceutical company focused on the research, development and commercialization of antiinfective products that meet unmet medical needs. In the U.S., Cubist markets Cubicin(R) (daptomycin for injection), the first antibiotic in a new class of antiinfectives called lipopeptides. Cubist's pipeline includes HepeX-B(TM), a monoclonal antibody biologic currently in the second of two Phase 2 trials to determine its potential for the prevention of infection by the Hepatitis B virus (HBV) in liver transplant patients, and research efforts focused on novel members of the lipopeptide class of molecules. Cubist is headquartered in Lexington, MA.

About XTLbio

XTLbio is a drug development company committed to developing therapeutics for viral hepatitis. XTLbio's HepeX(TM) product line based on human monoclonal antibodies (now in clinical trials) has the potential to introduce therapies for prevention of re-infection with hepatitis B and C virus in patients following liver transplantation.

In addition, the Company has a pre-clinical small molecule research program directed at chronic hepatitis C. The leading compound in this program is an HCV polymerase inhibitor, presently in late stage pre-clinical development.

XTLbio believes its primary competitive advantage lies in its patented Trimera(R) technology, which enables the development of fully human monoclonal antibodies and models of human disease for pre-clinical drug validation. Established in 1993, XTLbio became a public company in 2000 with shares traded on the London Stock Exchange under the symbol XTL.

Safe Harbor Statement

Statements contained herein that are not historical fact may be forward-looking statements within the meaning of Section 27A of the Securities Act of 1933 and Section 21E of the Securities Exchange Act of 1934, and such statements are subject to a variety of risks and uncertainties. There are a number of important factors that could cause actual results to differ materially from those projected or suggested in any forward-looking statements made by Cubist. These factors include, but are not limited to: (i) the level of acceptance of CUBICIN by physicians, patients, third-party payors, and the medical community generally; (ii) Cubist's ability to continue to develop, secure additional regulatory approvals for, and successfully market, CUBICIN; (iii) Cubist's ability to manufacture CUBICIN on a commercial scale; (iv) commercialization of products that are competitive with CUBICIN; (v) Cubist's ability to discover or in-license drug candidates; (vi) Cubist's ability to successfully develop drug candidates in its pipeline, including HepeX-B; (vii) Cubist's ability to successfully commercialize any product or technology developed by Cubist; (viii) Cubist's ability to establish and maintain successful manufacturing, sales and marketing, distribution, and development collaborations; (ix) legislative or regulatory changes adversely affecting Cubist or the biopharmaceutical industry; (x) Cubist's ability to protect its intellectual property and proprietary technologies; and (xi) Cubist's ability to finance its operations. Additional factors that could cause actual results to differ materially from those projected or suggested in any forward-looking statements are contained in Cubist's recent filings with the Securities and Exchange Commission, including those factors discussed under the caption "Risk Factors" in such filings.

Cubist and Cubicin are registered trademarks of Cubist Pharmaceuticals, Inc.; HepeX-B is a trademark of XTL Biopharmaceuticals Ltd.

Additional information can be found at Cubist's web site at www.cubist.com