 - Patients must have completed all previous anti-leukemic therapy for at least 2 weeks, except as noted, and have fully recovered from side effects of a previous therapy, unless disease progression necessitates early therapy. Patients may receive leukapheresis, hydroxyurea and anagrelide for up to 24 hours prior to start of study treatment. Patients receiving imatinib mesylate may continue to receive it uninterrupted, except for a 3-day window at treatment cycle 1. 