Comparing tyrosine kinase inhibitors: Higher treatment response rates with dasatinib than with imatinib

This study compared the effectiveness of two types of tyrosine kinase inhibitors – imatinib (Gleevac) and dasatinib (Sprycel) – for the first-line treatment of chronic myeloid leukemia (CML). Researchers reported superior treatment response with dasatinib than with imatinib.

Targeted therapy is the standard first-line treatment for CML. This refers to a type of treatment that uses drugs or small molecules that block the growth and spread of cancer. Tyrosine kinase inhibitors are a type of targeted therapy that block enzymes called tyrosine kinases. Imatinib and dasatinib are tyrosine kinase inhibitors commonly used to treat CML. Dasatinib is more often used as a second-line treatment in patients who did not respond to imatinib. Whether imatinib or dasatinib is more effective as a first-line treatment for chronic (early) phase CML is still being investigated.

Treatment response is often measured based on patients showing less abnormal chromosomes (cytogenetic response) or genetic abnormalities (molecular response) in the blood or bone marrow. Major molecular response is often considered the main goal of CML treatment.

The aim of this study was to compare treatment response rates between imatinib and dasatinib.

519 patients with newly diagnosed chronic-phase CML were included in this study. Patients were randomly assigned to either receive treatment with imatinib or with dasatinib. Treatment response rates at 12 months were compared between treatment groups.

The rate of complete cytogenetic response at 12 months was higher with dasatinib (77%) than with imatinib (66%). The rate of patients achieving major molecular response at 12 months was also significantly higher with dasatinib (46%) than with imatinib (28%).

The time to a complete cytogenetic and major molecular response was significantly shorter with dasatinib. The likelihood of achieving an early treatment response was 50% to 100% greater with dasatinib. Among patients who achieved complete cytogenetic response by 12 months, the rate of also reaching major molecular response was significantly higher for dasatinib (54%) than for imatinib (39%).

Disease progression occurred in 5 patients who were receiving dasatinib (1.9%) and in 9 patients treated with imatinib (3.5%).

No significant differences in the rate of side effects was observed between the two treatment groups. Common side effects (in at least 10% of patients) included nausea, vomiting, muscle inflammation, rash, and fluid retention. Very low neutrophil levels occurred in 21% (dasatinib) and 20% (imatinib) of patients.

Researchers concluded that response to treatment occurred sooner and more strongly with dasatinib than with imatinib.