ATLANTAStudy results presented at ASH 2007 showed efficacy of the novel tyrosine kinase inhibitor dasatinib (Sprycel) in imatinib (Gleevec) resistant or intolerant chronic myelogenous leukemia patients in chronic, accelerated, and blast phase.
Richard M. Stone, MD, of the Dana-Farber Cancer Institute, presented 2-year follow-up data of the international phase II START-C trial (abstract 734). The study involved 387 patients with CP-CML who had imatinib resistance (n = 288) or intolerance (n = 99). Treatment consisted of dasatinib 75 mg twice daily.
With a median follow-up of 24 months, a complete cytogenetic response (CCyR) was achieved in 53% of patients and a major cytogenetic response (MCyR) in 62%. Nearly half of the patients (47%) experienced a major molecular response.
Overall survival at 24 months for the entire population was 94%, and for the imatinib-resistant and imatinib-intolerant populations, 92% and 100%, respectively. Progression-free survival rates for these three groups were 80%, 75%, and 94%, respectively.
"The drug appears to be active in a variety of patient subgroups examined," Dr. Stone said. Responses occurred across 42 different Bcr-Abl baseline mutations (but not T3151) and were achieved in patients with P-loop mutations and those with no prior cytogenetic response to imatinib.
Responses to dasatinib were durable, especially in patients with imatinib intolerance; 97% of those with MCyR sustained this response for more than 2 years.
At 24 months, severe (grade 3-4) hematologic toxicities consisted of leukopenia (27%), neutropenia (50%), and thrombocytopenia (49%).