Dasatinib (D) vs high dose imatinib (IM) in patients (pts) with chronic phase chronic myeloid leukemia (CP-CML) resistant to imatinib. Results of CA180017 START-R randomized trial

Abstract

6507 Background: High dose imatinib (800 mg/day) has been shown to have efficacy in a subset of CML patients with resistance to IM, although the durability of responses is not well-established. Dasatinib (BMS-354825) is a novel, highly potent, oral multi-targeted kinase inhibitor of BCR-ABL and SRC with activity against 18/19 imatinib resistant BCR-ABL mutants tested in vitro. Methods: START-R is a multicenter randomized (2:1 ratio) trial of D 70 mg twice daily (bid) and IM 800 mg/day in pts with CP-CML resistant to prior IM 400 to 600 mg/day. Cross-over was allowed for lack of response or intolerance (grade 3–4 non hematologic toxicity). D dose escalation to 90 mg bid was allowed for inadequate response at 12 wks, and dose reduction to 50 or 40 mg bid for drug toxicity. IM dose reduction to 600 mg/day was allowed. Evaluations consisted of weekly blood counts for the first 12 wks, bone marrow cytology and cytogenetics every 12 wks. The primary endpoint was major cytogenetic response (MCyR) rate at wk 12. Results: From February 2005 to November 2005, 150 pts were randomized of whom the first 36 pts (D 22, IM 14) are reported. Median age was 57 yrs, with 12 males and 24 females. Treatment groups were balanced with respect to CML characteristics; median time from initial diagnosis was 61 months for D and IM; prior interferon 64% and 79%; no prior CyR on IM 36% and 57%. BCR-ABL mutations were documented in 10 D pts and 1 IM pt. Dose reductions were required in 8 D pts and 1 IM pt. Complete hematologic response was documented in 21 D and 13 IM pts. MCyR rate at 12 wks was 45% for D and 21% for IM (7 complete for D and 1 for IM). With a 95% CI on the difference between D and IM was - 9.9 to +51.2. Two (9%) D and 11 (79%) IM pts crossed over for intolerance (1 D and 6 IM) or no MCyR (1 D and 5 IM). Grade 3–4 neutropenia or thrombopenia occurred in 8 and 9 dasatinib pts and in 8 and 2 IM pts. Most common grade 1–2 non-hematologic toxicities in D and IM groups were diarrhea (7 and 1 pts), nausea (7 and 7 pts), and facial/peripheral edema (8 and 7 pts). Conclusions: Dasatinib was effective in pts with CP-CML resistant to IM 400 to 600 mg/day. Preliminary data suggest that D is more effective and better tolerated than high dose IM. An updated analysis of all randomized pts will be presented. [Table: see text]