Phase II Study of Dasatinib In Patients with Relapsed Chronic Lymphocytic Leukemia.

Abstract 4488

Src-family kinases (SFK) are described to be over expressed in CLL resulting in increased BCR signaling. Aberrant activation of the SFK, Lyn, leads to defective apoptosis of CLL cells in-vitro. C-Abl kinase is also overexpressed in CLL cells compared to normal B-lymphocytes. Since dasatinib is a dual Src and c-abl kinase inhibitor with in-vitro pro-apoptotic properties in CLL cells, we investigated the activity of dasatinib in patients (pts) with CLL. We designed a phase II study of dasatinib in pts with relapsed CLL/SLL and T-PLL. Pts were eligible if they were previously treated and had indication for therapy according to NCI-working group criteria. All pts had adequate performance status, renal and liver function prior to therapy. Treatment consisted of dasatinib 50mg given orally twice daily. In case of suboptimal response the dose of dasatinib could be increased up to a maximum dose of 70mg twice daily. Dose reductions to 20mg twice daily were permitted for toxicity. Pts were assessed for treatment response according to 1996 NCI-WG criteria. Seventeen pts have been enrolled in this study. The median age was 67 years (42-83 years), 9 (52%) had Rai stage III-IV, median beta-2 microglobulin levels was 5.9 (3.0 – 11.8) mg/L. The median number of prior treatments was 4 (1 – 8). An objective response (PR) was observed in 1 patient, 13 pts had no objective response and 3 pts were not evaluable for response due to early discontinuation of therapy (0-3 days). Fourteen pts remained on therapy for a median of 2 (0-19) months with 4 pts discontinuing due to disease progression and 9 pts discontinuing due to adverse events and lack of response. Hematological toxicities consisted of grade 3–4 neutropenia in 76% of the pts, grade 3–4 thrombocytopenia in 44% of pts and grade 1–2 anemia in 80%. Non-hematological toxicity consisted of grade 3–4 fatigue in 1 patient and grade 3 pleural effusions in another patient. Grade 1 and 2, toxicities included flushing 38%, headache 38%, fatigue 46% anorexia and nausea 46%, and diarrhea 23%. Several pts showed evidence of biological activity. Treatment with dasatinib lacks efficacy in pts with heavily pretreated CLL. Responses occurred in only 6% of pts and dasatinib administration was associated with a high incidence of neutropenia.