Sprycel® Superior to High-dose Gleevec® for Gleevec-resistant CML

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leukemia cellsAccording to results presented at the 2006 annual meeting of the American Society of Hematology, treatment with Sprycel® (dasatinib) provides superior outcomes compared to escalated doses of Gleevec® (imatinib) in patients with chronic myeloid leukemia (CML) who have stopped responding to previous treatment with standard doses of Gleevec.

Chronic myelogenous leukemia (CML) is a cancer that originates in the immune cells. It affects approximately 4,600 people annually in the U.S. In the case of CML, large numbers of young immune cells do not mature, resulting in an excess accumulation of these cells. These leukemia cells then crowd the bone marrow and blood, suppressing formation and function of other blood cells normally present in these areas. In addition, the leukemia cells cannot perform their function properly, leaving patients susceptible to infection.

Chronic myelogenous leukemia begins with a chronic phase, during which few clinical problems, if any, occur. However, when left untreated, the chronic phase progresses into acute phases; these phases, called the accelerated and blastic phases, are characterized by fast-growing and aggressive cancer. Patients reaching these acute phases have a poor prognosis for long-term survival.

Philadelphia chromosome-positive (Ph-positive) CML refers to the majority of cases of CML in which a genetic abnormality, referred to as the Philadelphia chromosome, results in the constantly activated growth of cancer cells. Roughly 30% of adult patients with acute lymphocytic leukemia (ALL) also have this genetic abnormality.

Gleevec is a biological agent that binds to and slows or stops the uncontrolled growth of cancer cells with the Philadelphia chromosome genetic mutation. Unfortunately, a small number of patients stop responding to Gleevec and/or are not able to tolerate treatment with Gleevec. Researchers are evaluating new therapies for these patients. Research has indicated that some patients who stop responding to standard doses of Gleevec will experience anticancer activity if the doses of Gleevec are escalated.

Sprycel is an oral agent that has recently been approved by the U.S. Food and Drug Administration. It is targeted against multiple conformations of the genetic abnormalities in Philadelphia chromosome-positive leukemia. Sprycel stops the production of proteins involved in cancer growth.

Researchers affiliated with the START-R trial recently conducted a study to compare Sprycel to increased doses of Gleevec among patients with CML who had stopped responding to standard doses of Gleevec. This study included patients with chronic-phase CML who had stopped responding to prior therapy with Gleevec. These patients were subsequently treated with either Sprycel or increased doses of Gleevec.

  • Among patients who had achieved a major cytogenetic (chromosomal) anticancer response with previous therapy including standard-dose Gleevec, 35% achieved a complete cytogenetic response to Sprycel, compared with only 7% of those treated with escalated doses of Gleevec.
  • Among patients who did not achieve a cytogenetic anticancer response with standard-dose Gleevec, 44% achieved a major cytogenetic response to Sprycel, compared with only 7% of those treated with escalated doses of Gleevec.
  • No patients who crossed over from the Sprycel group to the higher-dose Gleevec group demonstrated a major cytogenetic response; however, 45% of patients who crossed over from the higher-dose Gleevec group to the Sprycel group demonstrated a major cytogenetic response.
  • The main side effect of Sprycel was low levels of blood cells, which may be partly corrected with the use of Neulasta.

The researchers concluded that Sprycel provides superior responses compared to increased-doses of Gleevec among patients with chronic-phase CML who have stopped responding to prior therapy with standard-doses of Gleevec. Patients with CML who have stopped responding to Gleevec may wish to speak with their physician regarding their individual risks and benefits of treatment with Sprycel.

Reference: Shah N, Pasquini R, Rousselot P, et al. Dasatinib (Sprycel®) vs escalated dose of imatinib (im) in patients (pts) with chronic phase chronic myeloid leukemia (CP-CML) resistant to imatinib: Results of the CA180-017 START-R randomized study. Proceedings from the 2006 annual meeting of the American Society of Hematology. December 2006.  Blood. 2006;108:53a. Abstract 167.

source Cancer Consultants 

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