A cancer-fighting drug developed in Oxford has been approved as a new treatment for leukaemia patients.

The medicine, known commercially as Campath, will now be used by doctors in America to treat people suffering from chronic lymphocytic leukaemia - the most common form of the blood cancer to affect adults.

Doctors expect it to be approved for UK use by the end of the year.

The American approval comes after clinical trials at the John Radcliffe Hospital, where a third of patients who had not responded to chemotherapy showed signs of improvement after using Campath.

The treatment has been developed at the Therapeutic Antibody Centre, based at the Churchill Hospital, in Headington, since 1995, when the research team moved to Oxford from Cambridge.

It works by protecting a patient's blood stream, bone marrow and organs by detecting and destroying cancerous white blood cells.

It also attacks healthy white blood cells, which although leaving patients susceptible to infection, could mean it proves useful for other conditions, like multiple sclerosis.

Prof Geoff Hale, Therapeutic Antibody Centre research director, said: "This is a key moment because it is now on sale in America and people can be treated with it and a lot more trials will be done.

"Once it is approved in Europe, this will be extended and continue. I feel thrilled about this because I have been working on it for more than 20 years."

Prof Hale said experts had already advised the European Agency for the Evaluation of Medicinal Products to approve Campath for use across Europe.

He said: "At the moment, Campath is being used as a third-line treatment - for patients who have tried everything else. But we are continuing to look at ways of using it as a front-line treatment.