Rehovot, Israel - XTL Biopharmaceuticals Ltd. is about to start a Phase I clinical study in the U.S. and Israel of XTL001, a combined double human monoclonal antibody.

This dose-ranging study includes 15 chronically infected hepatitis B virus patients, divided into five dose groups. The patients' viral load and general tolerance will be monitored at several intervals to determine antiviral activity and safety. The company expects the trial will be followed immediately by a Phase Ib dose-escalation study.

XTL001 is the company's lead compound and the first to be discovered and developed using its proprietary TrimeraXTL system. The system enables a normal mouse to live with a functional human liver, and thus to generate high-affinity, fully human monoclonal antibodies within a few weeks.

Preclinical studies have shown XTL001 acts at multiple distinct sites on the HBV surface antigen to neutralize the virus and limit viral escape. It binds with a high degree of specificity, enabling it to effectively neutralize the virus and also acts synergistically in combination therapy to reduce viral loads for an extended duration.

"This is the first of our drug candidates to enter clinical trials," said Martin Becker, president and CEO of XTL. "The initiation of this study validates our unique approach of generating novel MAb therapeutics as well as validating them in this versatile system. We are excited to be working with" the University of California-San Francisco, Stanford University in Palo Alto, Calif., and the Hadassah University Hospital in Jerusalem "following the very encouraging results of preclinical studies."