The MTD was to be the highest dose level of clofarabine in combination with etoposide and cyclophosphamide that caused <= 1 of 6 participants to experience a dose limiting toxicity (DLT) with the next higher dose level having at least 2 of 3 or 2 of 6 participants experiencing a DLT. The MTD would be used as the recommended phase 2 dose (RP2D). If the MTD could not be determined, then the target dose of clofarabine 40 mg/m^2, etoposide 100 mg/m^2 and cyclophosphamide 440 mg/m^2 as taken by Cohort 5 was to become the RP2D.

The rating scale used is 0 = not the MTD, 1 = the MTD.

All phase 1 participants

The number of participants in each cohort that had dose limiting toxicity is summarized. Toxicities were reviewed by an independent Data Safety Monitoring Board (DSMB) who determined if additional participants should be added to the cohort and the criteria for escalating to the next cohort.

All phase 1 participants

Number of participants with AEs that occurred during treatment and follow-up period (45 days after last cycle). Drug-related AEs and SAEs were followed until resolved or mutually agreed by the investigator and Genzyme to discontinue reporting. AEs were classified by the investigator according to severity (graded using National Cancer Institute [NCI] Common Terminology Criteria for Adverse Events [CTCAE] version 3.0) and relationship to study drug. The severity scale is:> Grade 1=Mild, Grade 2=Moderate, Grade 3=Severe, Grade 4=Life-threatening or disabling, Grade 5=Death related to AE

All phase 1 participants

Response categories 1) complete remission (CR): without circulating blasts or extramedullary disease, bone marrow (BM) with <5% blasts, and platelet (plt)/ANC recovery: ALL ≥75/ ≥0.75 [x 10^9/L]; AML ≥100/ ≥1.0 [x 10^9/L] 2) CR in absence of plt recovery (CRp): ALL plt ≥20 to <75 x 10^9/L; AML plt ≥20 to <100 x 10^9/L 3) partial remission (PR): no circulating blasts, appearance of normal hematopoietic progenitors, and either a BM with ≥5% and ≤25% blasts with recovery of plts/ANC or a BM with <5% blasts not meeting CR/CRp definition 4) Overall remission (OR): CR+CRp 5) Any response: CR+CRp+PR.

All phase 1 participants

The weeks between start of intervention and remission as assessed by the investigator in Phase 1. Participants who had a complete remission (CR) or complete remission with the absence of total platelet recovery (CRp) are included.

Participants in phase 1 who had an overall remission.

Duration of response is the time from the first objective measurement of complete response (CR) or complete response with the absence of total platelet recovery (CRp) to the date of first objective documentation of disease relapse or death due to any cause, plus one day. For summary purposes, results are presented as weeks.

Phase 1 participants who achieved overall remission. Data are censored at date of last known follow-up visit.

Event-free survival (EFS) is defined as the time from date of first administration of study interventions until the earliest of the following: date of death or date of first response assessment confirming relapse or date of final response assessment which fails to confirm response, plus one day. For summary purposes, results are presented as weeks.

All phase 1 participants. Data are censored at date of last known follow-up visit.

Number of participants with event-free survival at four months post first dose of therapy. A participant is considered event-free if at month 4 they have not died or had a response assessment confirming a relapse.

All participants

Overall survival is defined as the time from date of first administration of study interventions until date of death, plus one day. For summary purposes, results are presented as weeks.

All phase 1 participants

Response categories 1) complete remission (CR): without circulating blasts or extramedullary disease, bone marrow (BM) with <5% blasts, and platelet (plt)/ANC recovery: ≥75/ ≥0.75 [x 10^9/L] 2) CR in absence of plt recovery (CRp): plt ≥20 to <75 x 10^9/L 3) partial remission (PR): no circulating blasts, appearance of normal hematopoietic progenitors, and either a BM with ≥5% and ≤25% blasts with recovery of plts/ANC or a BM with <5% blasts not meeting CR/CRp definition 4) Overall remission (OR): CR+CRp 5) Any response: CR+CRp+PR.

All phase 2 participants

Number of participants with AEs that occurred during treatment and follow-up period (45 days after last cycle). Drug-related AEs and SAEs were followed until resolved or mutually agreed by the investigator and Genzyme to discontinue reporting. AEs were classified by the investigator according to severity (graded using National Cancer Institute [NCI] Common Terminology Criteria for Adverse Events [CTCAE] version 3.0) and relationship to study drug. The severity scale is:> Grade 1=Mild, Grade 2=Moderate, Grade 3=Severe, Grade 4=Life-threatening or disabling, Grade 5=Death related to AE

All phase 2 participants

The weeks between start of intervention and remission as assessed by the investigator in Phase 2. Participants who had a complete remission (CR) or complete remission with the absence of total platelet recovery (CRp) are included.

Participants in phase 2 who had an overall remission.

Duration of response is the time from the first objective measurement of complete response (CR) or complete response with the absence of total platelet recovery (CRp) to the date of first objective documentation of disease relapse or death due to any cause, plus one day. For summary purposes, results are presented as weeks.

Phase 2 participants who achieved overall remission. Data are censored at date of last known follow-up visit.

Event-free survival (EFS) is defined as the time from date of first administration of study interventions until the earliest of the following: date of death or date of first response assessment confirming relapse or date of final response assessment which fails to confirm response, plus one day. For summary purposes, results are presented as weeks.

All phase 2 participants. Data are censored at date of last known follow-up visit.

Number of participants with event-free survival at four months post first dose of therapy. A participant is considered event-free if at month 4 they have not died or had a response assessment confirming a relapse.

All participants

Overall survival is defined as the time from date of first administration of study interventions until date of death, plus one day. For summary purposes, results are presented as weeks.

All phase 2 participants. Data are censored at date of last known follow-up visit.