Study cohort
The study included seven patients with refractory acute leukemia: two males and five females aged 3 to 16 years. Five of the patients were diagnosed with ALL (four BCP-ALL and one T-ALL ) and two with AML (one de novo and one sAML after previous treatment of BCP-ALL). All patients had active disease, i.e., > 5% of leukemic blasts in bone marrow at the time of enrollment. One patient had primary refractory disease and never achieved complete remission before the first course of CloEC. One patient had a very early relapse of T-ALL (while on treatment) and was recruited directly to the study. The remaining patients had either first or subsequent refractory relapse and had failed two or more lines of treatment, in two patients including allogeneic HSCT. Characteristics of the patients are presented in Table 1.