Glivec is one of a new range of cancer medicines known as "smart drugs" which target cancer cells but leave normal ones alone.
Doctors describe it as a breakthrough in the treatment of chronic myeloid leukaemia (CML). Results announced in May of a clinical trial comparing Glivec to the standard
drug treatment of interferon alpha and chemotherapy showed that on one measure Glivec was nearly three times more effective.
A major disappearance of leukaemia cells was achieved in 84 per cent of Glivec patients, compared with 30 per cent in the standard-treatment group. Complete disappearance of cancer cells occurred in 69 per cent of Glivec patients, compared with 11.5 per cent of the standard-treatment group.
CML is caused by an abnormality in the DNA of the blood stem cells in bone marrow, which leads to further cell abnormalities.
The so-called Philadelphia chromosome, an abnormality, is formed. It contains an aberrant gene, Bcr-Abl, which produces an abnormal protein, an enzyme called a tyrosine kinase.
This protein drives uncontrolled production of white blood cells in the bone marrow, leading to a huge increase in their numbers in the blood.
Glivec interferes with the signal of the tyrosine kinase enzyme that promotes cancer cell growth. Patients with CML have two possible treatments - a bone marrow transplant or drug therapy.
However, transplants are available to only 30 per cent of patients, either because their age would make the operation too risky or because a suitable donor cannot be found.
Patients who have injections of the drug interferon report side effects such as diarrhoea, vomiting, lack of energy, loss of appetite, chronic pain, memory loss and hair loss.
Patients taking Glivec capsules in trials have also reported problems such as nausea, muscle cramps and skin rashes.
However, patients who have used both drugs report the side effects of interferon are far worse than those of Glivec.
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