Dasatinib (SPRYCEL®, formerly BMS-354825) is a potent, orally active, multi-targeted kinase inhibitor active against BCR-ABL and SRC family kinases. Studies outside Japan have demonstrated that dasatinib is highly effective in overcoming resistance and intolerance to imatinib (im), inducing durable cytogenetic and hematologic responses in this CML patient population. In establishing the dose for non-Japanese patients, the maximum tolerated dose failed to be reached and the 70-mg-twice-daily (BID) dose was determined to provide the optimal benefit-risk profile. Based on clinical experience to date, dasatinib has the potential to have a major impact on the current treatment paradigm for patients with CML resistant or intolerant to prior therapy, including im. To assess the safety and efficacy of dasatinib in Japanese patients, a phase-I/II study was conducted in patients with all phases of im-resistant or -intolerant CML. In the phase-I portion of this study, dasatinib was administered at one of three escalating dose levels for a period of 4 weeks: 50 mg, 70 mg, or 90 mg BID. As of July 2006, 15 eligible patients have been enrolled and treated. Six evaluable patients (4F, 2M; median age 43 y [range 27–56]; 4 im-resistant, 2 im-intolerant) were treated at the 50 mg BID dose level and one dose-limiting toxicity (DLT) was observed (grade 4 thrombocytopenia). Two patients experienced transient grade 3 ALT elevations but as treatment was uninterrupted, these were not considered DLTs. A further 6 evaluable patients (6M; median age 42 y [range 27–55]; 3 im-resistant, 3 im-intolerant) were treated at the 70 mg BID dose level and one DLT was observed (grade 4 thrombocytopenia). Three patients have recently been enrolled at the 90 mg BID dose level. As the safety of the 70 mg BID dose was established in the phase-I portion of the study, the use of this dose is being expanded into the phase-II element, which plans to evaluate cytogenetic response in chronic phase CML patients at 24 weeks, and hematologic response rate in accelerated- or blast-phase CML and Philadelphia chromosome-positive acute lymphoblastic leukemia (Ph+ ALL) patients at 12 weeks. Accrual to the phase-II portion of this study is ongoing. Updated data including baseline mutational analyses will be presented at the meeting.

Disclosures: Bristol Myers Squibb.; Bristol-Myers Squibb.

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