Efficacy of Dasatinib in Patients (pts) with Previously Untreated Chronic Myelogenous Leukemia (CML) in Early Chronic Phase (CML-CP)

Background: Dasatinib (BMS-354825) is a multi-targeted kinase inhibitor of BCRABL and SRC with significant activity in pts with CML-CP resistant to or intolerant of imatinib (IM). We initiated a phase II trial to study efficacy and safety of dasatinib in pts with previously untreated CML-CP.

Aims: To investigate the efficacy and safety of dasatinib as initial therapy for patients with CML-CP.

Methods: The primary objective was to estimate the proportion of pts attaining major molecular response (MMR) at 12 months (mo). Pts with previously untreated CML-CP were eligible and received dasatinib 100 mg/day, randomized to either 50 mg-twice-daily (BID) or a 100 mg-once-daily (QD).

Results: Fifty pts have been enrolled (25 on the QD schedule, 25 BID). Median age was 45 years (yrs) (range 18–76 yrs); 75% are Sokal low risk. Median follow-up is 24 months (mo). Overall, 44/45 (98%) evaluable patients achieved complete cytogenetic response [CCyR]. The CCyR rate at 3, 6 and 12 mo compares favorably to that observed in historical controls treated with imatinib 400mg or 800 mg daily:

MMR was achieved in 12/35 (34%) at 12 mo and 12/25 (48%) at 18 mo. One of 46 (2%) evaluable pts have achieved confirmed complete molecular response, and 1 other unconfirmed (ie, only achieved on their last assessment). Grade 3–4 non-hematologic toxicity (regardless of causality) included pruritus (13%), fatigue (6%), neuropathy (4%), and memory impairment (4%). Pleural effusion occurred in 21% evaluable pts (grade 3–4 in 2%). Grade 3–4 hematologic toxicity (transient) was thrombocytopenia in 11%, neutropenia in 21%, and anemia in 9%. Twenty-seven (54%) pts required transient treatment interruption. The actual median daily dose for all pts was 100mg. There is no significant difference in grade 3–4 toxicity by treatment schedule. Four pts came off study: 1 pts choice after 1 dose, 1 for toxicity (pleural effusion, QD schedule), and 2 lost response after multiple treatment interruptions (1 myelosuppression, 1 pleural effusion, both BID schedule). Two other pts have lost response because of non-compliance. 24 month EFS (event = loss of CHR, loss of MCyR, AP/BP, death, or off because of toxicity) is 81%.

Conclusion: Rapid CCyR occurs in most patients with previously untreated CML-CP treated with dasatinib frontline therapy with a favorable toxicity profile. Accrual to this trial continues.