Swiss drug major Novartis has reported data revealing that its cancer drug Glivec/Gleevec has excellent long-term efficacy, although an independent study linking the drug to bone loss took some of the shine off the finding.

Data compiled from long-term users of Glivec (imatinib) for chronic myeloid leukaemia, four and a half years since the drug has been in use, show that more than 90% of patients taking the drug continued to survive and were free from progression to advanced disease.

A five-year update from the IRIS study (International Randomized Interferon versus STI571), the largest clinical trial to date for newly-diagnosed adult patients with Philadelphia chromosome-positive (Ph+) chronic myeloid leukemia, will be presented at the American Society of Clinical Oncology meeting on June 3.

Before Glivec was available, about 50% of patients with this disease progressed to the more advanced stages of Ph+ CML after only three to five years, and survival was generally short for those patients.

Novartis noted that the drug's unprecedented outcomes in Ph+ CML patients includes reduced annual progression rate with long-term use in newly-diagnosed CML patients, as well as less than 1% progress to more advanced stages in the fourth treatment year. The firm stated that no other drug for this disease has ever established such a proven and durable track record of efficacy and safety.

Meanwhile, a small study reported in the New England Journal of Medicine has suggested that Glivec can interfere with bone remodeling. The side effect was discovered after researchers at Memorial Sloan-Kettering Cancer Center in New York, USA, found a number of patients on imatinib who had low serum phosphate levels. The significance of the finding is not yet clear.