All patients will receive the same doses of etoposide and cyclophosphamide. The dose of clofarabine will be escalated in successive cohorts of patients. Using a standard dose escalation design, successive cohorts of 3 patients will be treated with escalating doses of clofarabine (see Section 5.5 below). At the MTD (or highest dose-level if the MTD is not reached), the cohort will be expanded to 10 patients to better investigate correlative studies and give some preliminary idea of efficacy.
