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High Dose Imatinib Achieved Better Response Rates Than Standard Dose in Chronic Myeloid Leukemia
Researchers found that 53% of evaluable patients with newly diagnosed CML who were taking 800 mg of Gleevec achieved a CCR at three months compared to 37% of patients who were taking the standard dose. At 12 months, 92% of evaluable patients taking 800 mg achieved a CCR compared to 72% of those taking the standard dose. A CCR is the elimination of cells containing the Ph chromosome, the genetic abnormality that characterizes most cases of CML. CCR is a major goal of therapy.
"Previously published data of other therapies suggest that the earlier patients achieve a CCR, the better their prognosis," said Jorge Cortes, Associate Professor of Medicine and Deputy Chair, Department of Leukemia, The University of Texas, M.D. Anderson Cancer Center. "If confirmed, these early results may provide a new approach for initial treatment."
In addition to more rapid CCR, researchers found that more patients achieved a molecular response with 24% (15/62) patients achieving undetectable Bcr-Abl at the higher dose (800 mg/day) compared to 5% (2/43) patients taking the standard dose (400 mg/day). Molecular response is a relatively new and more sensitive tool capable of detecting extremely minute quantities of residual leukemia cells in the body following treatment. Molecular response may prove a possible new benchmark for evaluating drug therapy effectiveness and prognosis.
In two consecutive trials in patients with previously untreated newly diagnosed Ph+ CML, researchers treated 167 patients with previously untreated CML in early chronic phase with Gleevec. One trial included 50 patients treated with the standard dose of Gleevec (400 mg/day). The other trial included 117 patients treated with a total daily dose of 800 mg. At 12 months, 105 patients were evaluable (43 at the 400 mg dose and 62 at the 800 mg dose).
The median follow-up for patients treated at the standard dose was 24 months while the median follow-up for patients treated at the 800 mg dose was 13 months. Although side effects were similar with the two dose schedules, myelosuppression was more common at the higher dose, with grade greater than or equal to 3 anemia, neutropenia and thrombocytopenia occurring in 10%, 35%, and 25% of patients treated with 800 mg, respectively, versus 4%, 20% and 10% of patients treated with 400 mg, respectively. Generally, in most patients side effects such as neutropenia were transient and did not require permanent dose reduction below 600 mg. At 12 months, the median actual dose for the group started at 800 mg was still 800 mg with 19% (15/79) of patients requiring dose reduction to 400 or 300 mg of Gleevec.
Gleevec is indicated for the treatment of newly diagnosed adult patients with Ph+ CML in chronic phase. Follow-up is limited. Gleevec is also indicated for the treatment of patients with Ph+ CML in blast crisis, in accelerated phase, or in chronic phase after failure of interferon-alpha therapy. Gleevec is also approved for the treatment of pediatric patients with Ph+ chronic phase CML whose disease has recurred after stem cell transplant or who are resistant to interferon-alpha therapy.
In February 2002, just nine months following the initial CML approval, Gleevec received FDA approval for the treatment of patients with Kit (CD 117) positive unresectable (inoperable) and/or metastatic malignant gastrointestinal stromal tumors (GISTs). The effectiveness of Gleevec in GIST is based on the objective response rate. In the pediatric indication, the original CML indication and in the GIST indication in adults, there are no controlled trials demonstrating a clinical benefit, such as improvement in disease-related symptoms or increased survival.
Gleevec is approved as Glivec(R) (imatinib) in the EU, Switzerland and other countries.
Contraindications, Warnings and Adverse Events
The majority of CML patients who received Gleevec in clinical studies experienced adverse events, but they were usually mild or moderate. The most frequently reported adverse events (all grades) regardless of suspected relationship to treatment were superficial edema (53%-71%), nausea (43%-71%), diarrhea (30%-55%), muscle cramps (27%-55%), musculoskeletal pain (34%-46%), rash (32%-44%), and abdominal pain (23%-33%). In most cases, these events were managed without having to reduce the dose of Gleevec or interrupt treatment. Gleevec was discontinued because of adverse events in only 2% of patients in chronic phase, 3% in accelerated phase, and 5% in blast crisis.
Severe (NCI Grades 3/4) neutropenia (2%-48%), thrombocytopenia ( In the GIST trial that was the basis for GIST approval, drug was discontinued for adverse events in six patients (8%). In this clinical trial, the most common adverse events were edema, nausea, diarrhea, abdominal pain, muscle cramps, fatigue and rash. In this trial, seven patients (5%) were reported to have gastrointestinal bleeds and/or intratumoral bleeds. Gastrointestinal tumor sites may have been the source of GI bleeds.
Use of Gleevec is contraindicated in patients with hypersensitivity to imatinib or to any other component of Gleevec.
Women of childbearing potential should be advised to avoid becoming pregnant while taking Gleevec.
Gleevec should be taken with food and a large glass of water to minimize GI irritation.
Dose adjustments may be necessary due to hepatotoxicity, other nonhematologic adverse events, or hematologic adverse events.
Gleevec is metabolized by the CYP3A4 isoenzyme and is an inhibitor of CYP3A4, CYP2D6, and CYP2C9. Please see full Prescribing Information for potential drug interactions.
Patients should be weighed and monitored regularly for signs and symptoms of edema, which can be serious or life threatening.
Numbers indicate the range in percentages in 4 studies among patients with CML in blast crisis, accelerated phase, and chronic phase.
Source: Novartis, Inc.