Comparing tyrosine kinase inhibitors: Higher response rates with radotinib than with imatinib

This study compared the effectiveness of two types of tyrosine kinase inhibitors – imatinib (Gleevac) and radotinib (Supect) – for chronic myeloid leukemia (CML). Researchers concluded that response to treatment occurred sooner and more strongly with radotinib than with imatinib.

Tyrosine kinase inhibitors, such as imatinib (Gleevac), are a common first-line treatment for CML. This refers to a type of targeted therapy that block enzymes called tyrosine kinases. Radotinib is a more recently developed tyrosine kinase inhibitor. Whether imatinib or radotinib is more effective in treating 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.

241 newly diagnosed CML patients were randomly assigned to treatment groups. 79 patients were treated with 300 mg of radotinib. 81 patients received 400 mg of radotinib. 81 patients were treated with imatinib. All patients included were positive for the Philadelphia chromosome (a genetic abnormality that can make CML more difficult to treat).

Major molecular response at 12 months was observed in 52% of patients in the 300 mg radotinib group and in 46% of patients in the 400 mg radotinib group. This was significantly higher compared to patients treated with imatinib (30%). The average time to major molecular response was faster for radotinib at 300 mg (5.7 months) and radotinib at 400 mg (5.6 months) versus imatinib (8.2 months).

Complete cytogenetic response rates at 12 months were also significantly higher for patients treated with 300 mg of radotinib (91%) compared to imatinib (77%).

At 12 months, there were no cases of progression to a more advanced disease stage (accelerated or blast crisis). Treatment-related side effects were observed in most patients (91 to 94%). The most common side effects were related to low white blood cell counts, of which 16 to 30% were considered serious. Most side effects were manageable with dose reduction.

This study concluded that radotinib was associated with better treatment outcomes compared to imatinib.

An author of this study received funding from manufacturers of radotinib.