Dose escalation continues in cohorts of 3-6 patients until the maximum tolerated dose (MTD) or minimum effective dose (MED) is determined. The MTD is defined as the dose preceding that at which 2 or more patients experience dose limiting toxicity. The MED is defined as the dose at which 4 of 6 patients achieve a complete cytogenetic or molecular response. After the MTD or MED is determined, an additional 20 patients are enrolled at this dose level.