A Study of Clofarabine and Cytarabine for Older Patients With Relapsed or Refractory Acute Myelogenous Leukemia (AML)(CLASSIC I)

Clofarabine (injection) is approved by the Food and Drug Administration (FDA) for the treatment of pediatric patients 1 to 21 years old with relapsed acute or refractory lymphoblastic leukemia (ALL) who have had at least 2 prior treatment regimens. There is no recommended standard treatment for relapsed or refractory acute myelogenous leukemia in older patients. Cytarabine is the most commonly used drug to treat these patients. This study will determine if there is benefit by combining clofarabine with cytarabine. Patients will be randomized to receive up to 3 cycles of treatment with either placebo in combination with cytarabine or clofarabine in combination with cytarabine. Randomization was stratified by remission status following the first induction regimen (no remission \[i.e., CR1 = refractory\] or remission \<6 months vs CR1 = remission ≥6 months). CR1 is defined as remission after first pre-study induction regimen. The safety and tolerability of clofarabine in combination with cytarabine and cytarabine alone will be monitored throughout the study.

After screening and eligibility assessment, patients were randomized (in a 1:1 ratio) to receive either clofarabine or matching placebo, in addition to cytarabine. Randomization was stratified by remission status following the first induction regimen (CR1): no remission \[i.e., CR1 = refractory\] or remission \<6 months vs remission ≥6 months. During randomization by interactive voice response system (IVRS), there were 10 participants misclassified to the CR1 \<6 months stratum and 12 participants misclassified to CR1 ≥6 months stratum. The error did not affect the participants' treatment, only the stratification. Due to the misclassification, outcomes that used strata in their analysis were analyzed twice: once with the 'randomized stratification' which includes the misclassification and once with the 'calculated stratification' in which participants appear in the 'correct' strata. Two clinical study reports were written for this study. 1. Clinical study report dated 7 April 2011 includes the entire treatment period of all participants plus much of the follow-up. At that time, 33 participants in the Clofarabine+cytarabine group and 29 participants in the placebo+cytarabine group were still being follow-up post treatment. Results were reported on clinicaltrials.gov in August 2011. Outcomes that used strata reported the 'calculated strata' on clinicaltrials.gov. 2. Clinical study report dated 9 July 2012 includes all patient treatment experience plus all long-term follow-up (a minimum of 2 years from the end of treatment or until the patient died). The study was completed at that time. Outcomes that used strata reported the 'randomized strata' on clinicaltrials.gov. AE records on clinicaltrials.gov reflect the final database. Outcomes that changed between the two clinical study reports due to the additional long-term follow-up data are reported twice on clinicaltrials.gov (once from each clinical study report) and the appropriate report date is included in the outcome description. Outcomes from the 9 July 2012 report represent more complete data.