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Imatinib Therapy Shows Positive Results After 4 Years in Chronic Myeloid Leukemia: Presented at ASH

By Mike Fillon

ATLANTA, GA -- December 14, 2005 -- Patients with chronic myeloid leukemia (CML) in complete cytogenetic response who had an adequate reduction in their BCR-ABL transcript levels after 1 year of imatinib treatment have a good chance of achieving a much greater reduction after 4 years.

The study updates the results of molecular monitoring of patients in the prospectively International Randomized Interferon versus STI 571 (IRIS) study that compared imatinib therapy with interferon-alfa plus cytarabine.

The IRIS study was initiated in June 2000 and showed that after 1 year of imatinib treatment an estimated 40% of CML patients who achieved complete response after taking 400 mg/day achieved a major molecular response (MMR), defined as substantial reduction in BCR-ABL levels.

In a report presented here December 12^th at the 47^th Annual Meeting of the American Society of Hematology (ASH), researchers presented data, which showed that patients treated with imatinib for 4 years had continued reduction in BCR-ABL transcript levels.

This latest analysis was based on 101 patients who achieved complete cytogenetic response (CCyR) within 1 year, received first-line treatment for at least 24 months, and had blood collected for measuring transcript numbers at 1 year and 4 years.

Results are expressed as a log reduction from a standardized baseline value for untreated patients. This means they are expressed as transcript copy numbers, with a 1-log reduction equivalent to a fall from 100 to 10, and a 2-log reduction equivalent to a fall from 100 to 1.

At 1 year, BCR-ABL transcript levels fell by at least 3 logs in 46% of the 101 patients. At the most recent measurement, at or after 44 months from start of study, 75% of patients demonstrated a reduction of at least 3 logs. Of these patients, more than half had already had a 3-log reduction at year 1, whereas 49% had not. Conversely, 8 of the 47 patients with 3-log reduction at 1 year had a greater than 3-log reduction at 4 years.

At the 1- and 4-year points, 20% and 36% of patients, respectively, achieved 4-log reductions.

"The results are gratifying and show that patients in complete cytogenetic response who had an adequate reduction in their BCR-ABL transcript levels at 1 year have a good chance at achieving a much greater reduction after 4 years of imatinib treatment," said John M. Goldman, MD, professor of hematology, Imperial College in London, United Kingdom, and Fogarty Scholar Hematology Branch, National Heart, Lung, and Blood Institute (NHLBI), Bethesda, Maryland.

"This is an important observation because it means that imatinib continues for at least 4 years to reduce the quantity of residual disease and so promises to offer patients with chronic phase CML very substantial prolongation of essentially normal life, compared with previous therapies," Dr. Golman said.


[Presentation title: Continuing Reduction in Level of Residual Disease After 4 Years in Patients With CML in Chronic Phase Responding to First-Line Imatinib (IM) in the IRIS Study. Abstract 163]

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