Almost 90 percent of patients with Philadelphia chromosome-positive (Ph+) chronic myeloid leukemia (CML) were alive five years after they began receiving Gleevec (imatinib), drugmaker Novartis announced at the recent 2006 annual meeting of the American Society of Clinical Oncology.

The 89.4 percent survival rate in the Phase III trial, which was started in June 2000, includes deaths from all causes, but only 4.6 percent of the patients died from causes related to their leukemia, Novartis said. Moreover, the yearly risk of progressing to advanced disease continued to decline to 0.6 percent in the fifth year. Before Gleevec became available, about half of all patients progressed to the more advanced stages of Ph+ CML after only three to five years, with poor prospects for survival.

"Gleevec is a targeted therapy," Geoffrey Cook of Novartis Oncology told FDAnews. The target is Bcr-Abl tyrosine kinase, which is one of the causes of the disease and is in turn caused by the Philadelphia chromosome genetic defect, named after two Philadelphia-based researchers who first identified it in the 1960s. The therapy "hits [the target] very well, with a very high binding ability," Cook said.

Gleevec, known as Glivec in some other countries, was formerly known as STI571. The International Randomized Interferon versus STI571 (IRIS) study is an open-label Phase III clinical trial enrolling 1,106 newly diagnosed patients with Ph+ CML in chronic phase in 177 centers across 16 countries. The results of the trial were so impressive early on that the company decided to break the original blind the study was operating under and make Gleevec available to patients who had been in the control group.