Clinical Efficacy and Safety Of Dasatinib For Newly Diagnosed Chronic Myeloid Leukemia In Chronic Phase In Japan

Dasatinib is a second-generation BCR-ABL inhibitor that has a 325-fold higher potency than imatinib and a 16-fold higher potency than nilotinib in vitro. The previous report from the global DASISION trial showed dasatinib resulted in significantly higher and faster rates of complete cytogenetic response (CCyR) and major molecular response (MMR) compared with imatinib. We conducted a phase II study to evaluate the efficacy and safety of dasatinib in patients with newly diagnosed chronic-phase chronic myeloid leukemia (CML-CP) in Japan.

Eighty newly diagnosed CML-CP patients were include in this study. Patients received dasatinib 100mg once daily. Treatment was continued until disease progression or unacceptable toxicity. Primary end point was the rate of major molecular response (MMR) by 12 months. MMR defined as a BCR-ABL transcript level of 0.1% or lower on the International scale by means of a real-time quantitative reverse transcriptase-polymerase chain reaction (RT-PCR) in peripheral blood. Secondary end points were the rate of complete cytogenetic response (CCyR) by 12 months, the rate of MR^4.5 (either (i) detectable disease with <0.0032% BCR-ABL1 IS or (ii) undetectable disease in cDNA with >32,000 ABL1 transcripts in the same volume of cDNA used to test for BCR-ABL1) by 12 months and adverse events of dasatinib (UMIN #000006358).

Eighty newly diagnosed CML-CP patients were included in this study. All except one patient administered dasatinib 100 mg once daily. One patient was withdrawal before administration of dasatinib. So far, there were 71 patients with 6 months follow-up and 51 patients with 12 months follow-up. The estimated MMR rates were 69.5 % (95%CI, 58.7-80.3 %) by 6 months and 82.7% (95%CI, 73.0-92.4 %) by 12 months. The estimated MR^4.5 rates were 27.1 % (95%CI, 16.7-37.5 %) by 6 months and 48.9% (95%CI, 36.0-61.7 %) by 12 months. Only 6 patients were withdrawal because of adverse event (5 patients) and ineffectiveness (1 patient).

Dasatinib treatment results in higher rates of molecular responses in newly diagnosed CML-CP patients in Japan. Dasatinib as the first-line agent might be acceptable for CML-CP patients because of better clinical efficacy and less toxicity.

No relevant conflicts of interest to declare.