Pioneer in gene therapy wins pivotal patent

Innovation: first for Therexsys

THE UK's only company specialising in human gene therapy - treating disease by replacing faulty genes with healthy ones - will be granted a key patent this month on getting genes to the right place in the body.

The patent keeps the company, Therexsys, on target for a stock market flotation in two years. "This is a pivotal piece of intellectual property in the development of this new area of medicine," said Dr Roger Craig, chief executive.

It is a further boost for the high-risk biotechnology industry and follows the launch last week of a £9m scheme by Michael Heseltine, the President of the Board of Trade. He wants to see biotechnology used not just in the drugs industry but in areas from food manufacture to waste disposal.

Therexsys was set up in 1992 to commercialise research carried out by the state-owned Medical Research Council. After seed funding of £400,000 from 3i, Schroder Ventures and Biotechnology Investments, the company raised £6.4m in venture capital in November 1993.

"All the leading sponsors of biotechnology from the US, Europe and Japan are represented, demonstrating the significance of our technology," said Dr Craig.

Rather than granting a licence and waiting for royalties, the MRC has equity in Therexsys: licences granted to earlier biotech companies have failed to bring in any revenue so far for the research council.

There are two existing methods of trying to insert a therapeutic gene into humans. One involves putting the gene into a virus. Viruses survive by getting into the cells of a host and taking over the genetic machinery in order to reproduce themselves. In gene therapy, the viruses are disabled so they cannot replicate but still have the ability to slot the therapeutic gene into the cell nucleus. The worry is that the viruses could regain the ability to replicate, causing serious infections.

A second, less risky method, involves wrapping the genes in envelopes of fatty material called liposomes, which dissolve inside the body. The problem is that there is no way of targeting liposomes to the cells where the gene is needed.

Therexsys's approach, based on a string of genes called a locus control region (LCR), avoids these pitfalls. Each type of cell has a characteristic locus control region, which is responsible for switching on other genes.

The therapeutic gene is attached to the LCR of the target cell type and will only be switched on in these cells. Therexsys is also developing delivery systems based on proteins rather than viruses, to get the package of LCR and its attached gene into the cell.

To date, there are only two other human gene therapy companies in Europe. In the United States, there are 44.

The first clinical trials, which are due to take place towards the end of this year, will involve either an attempt to slow the progress of Aids by boosting T cells - the blood cells that fight the infection, or to treat Gaucher's disease. This is an inherited metabolic disorder caused by a single faulty gene.

The first treatments will be carried out ex vivo - blood will be removed from the patient and the therapeutic gene added before the blood is transfused back.

The genetic modification of blood cells "offers a scope of treatment possibly unequalled by any other physiological system in the body", said Dr Craig. The long-term aim is to develop injectable medicines.

Therexsys has spent £750,000 of its funds equipping a research laboratory and manufacturing facility, which opened at Keele University Science Park four months ago.

The company now has 21 staff and this will rise to 30 by the end of the year, when Dr Craig expects to begin another round of funding. On the current plan, the company will go public in 1997.

Although the first therapy will not reach the market before 2000-2001, Therexsys will set up licensing deals with pharmaceutical companies to develop its technology. The first deal will be signed this year. "This will be a relationship the investors can believe in," said Dr Craig.