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Of Mice and Man
Margo Lipschitz Sugarman
 (Avi Katz) |
In their cages, the lab mice of XTL Pharmaceuticals look much like any other rodents. Don�t be deceived. For one thing, they are among the very few mice worldwide with human tissue implanted in them; for another, they may hold a key to curing hepatitis B and hepatitis C, often fatal viral diseases of the liver which affect hundreds of millions of people all over the globe.
The mice - at XTL�s headquarters, in the Kiryat Weizman high-tech park just north of Rehovot - are the fulfillment of medical researchers� dreams, offering a duplication of human tissue in laboratory animals, to speed up the process of testing new drugs. Existing lab procedures, after all, only offer absolute proof that a specific material may be, say, either a carcinogen or a cancer cure in the species being tested. And what works on mice does not, of necessity, work on humans as well.
Technology developed by XTL, called Trimera, produces mice whose reactions to drugs replicate those of humans. Researchers can infect Trimera mice with a specific malady, to produce a "disease model" on which to test new cures. Or they can use the mouse�s simulated human immune systems to produce antibodies, which can then be replicated as the basis for new medicines. That�s what the seven-year-old company has already done with XTL001, a treatment for hepatitis B that is now undergoing first-stage testing on human patients at Hadassah Medical Center in Jerusalem, and at Stanford University and the University of California at San Francisco.
What�s more, the company�s literature suggests that Trimera mice-based pharmaceutical development is cheaper and faster than standard methods, substantially cutting the $500 million-range cost of bringing a new drug to market. And perhaps just as important, that it might cut down on unwanted side effects found in many pharmaceuticals.
XTL's base technology traces its history back to the immunology lab of Prof. Yair Reisner at the Weizmann Institute of Science in the early 1990s. Reisner was looking for a way to transplant bone marrow into human subjects from people who were not genetically related to them. Unable to experiment on humans, he found that under certain conditions, it was possible to implant mice with human tissue, which within a few weeks produces cells that turn out antibodies. In addition to inhibiting transplant rejection, Reisner was able to create "models" of diseases that can be used in developing artificial antibodies, and can increase the chances of clinical success in drug tests.
In the first stage of Trimera, a normal mouse is treated with radiation to destroy its natural immune system. It then gets bone marrow from another mouse to create a new blood-building system. Finally, human immune cells are implanted to establish a system that produces fully human antibodies.
XTL�s predecessor, Xeongraph Technologies, was founded in 1993 by Reisner and Yeda, the company set up by the Weizmann Institute to develop commercial applications for technologies developed by its academics. The goal, explains Dr. Martin Becker, president and CEO of the company, (which subsequently shortened its name to XTL) has been to find other uses for these mice with human tissue.
One of the early experiments involved introducing tiny particles of human liver into a mouse, and infecting it with hepatitis B. "Until then," says Becker, "it had been very difficult to make a model of hepatitis B. And without that model, it was nearly impossible to create a drug that would deal with it."
It was a major step. Becker, who spent 15 years with a Silicon Valley-based biotech firm before joining XTL, says that lab technologies often remain exactly that, without ever becoming commercial. In this case, there was the possibility of an end product that might be worth a lot of money some day. "My initial aim was to get the technology to work," he says, "and to develop a business strategy. We decided to focus on creating drugs for infectious diseases, a field in which we thought we�d have a competitive advantage."
Because XTL had already been able to develop disease models for hepatitis B and C, the company�s primary objective was to work on drugs for those two maladies. "The potential market for hepatitis B treatments amounts to about $500 million and the currently available treatments are not really effective," says Becker. "Only 40 percent of patients have responded to what�s on the market today."
The disease is a serious problem, he adds, being about 100 times more infectious than AIDS. Hepatitis B, the most common form of the hepatitis virus, can destroy the liver or stimulate the development of liver cancer in people who seem to be completely well. There are 1 million hepatitis B carriers in the United States alone, where 70,000 new cases are reported each year, and 350 million hepatitis B carriers around the world. In addition, says Becker, about 3.9 million Americans - and 200 million people worldwide - already suffer from equally dangerous hepatitis C.
XTL estimates that the market for hepatitis treatments exceeds $3 billion, which would give the firm huge growth potential. But that�s not the strategy that Becker has in mind. Instead, he sees XTL as a think-tank that uses its patented Trimera technology to develop drugs into the clinical testing phase required by the U.S. Food and Drug Administration and other regulatory bodies around the world, and then strike deals with large pharmaceutical companies which have the manufacturing capacity, the marketing apparatus, and the money to bring a drug to market, a process that invariably costs hundreds of millions of dollars. In exchange for its half-finished product, XTL would take a transfer fee, perhaps another fee when the drug goes on the market, and 15 percent royalties, which Becker says is the industry standard. So far, XTL has struck this kind of deal with Roche, Lilly and a third major pharmaceutical company Becker declines to name.
The company has attracted a number of well-known investors, including Rothschild and Nomura of the U.K., Medica of Israel, Lombard Odier of Switzerland, Goldman Sachs and Biotechvest of the U.S. So far there�s been no entry onto the stock market - though, Becker says, the firm started the process of offering its shares in London early this year, then called them off because of the weakness of the market.
Meanwhile, the company is exploring new areas of drug development: Treatments for fungus-based diseases that attack people with weak immune systems, for inhibiting the spread of tumors, and for dealing with bacteria with a high level of resistance to antibiotics. These might open up huge new markets to XTL. But Becker is sticking to the develop-and-license model, rather than entering the competitive field of production and marketing. It is, he insists, "the best risk-benefit situation for small companies."
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