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.

Eligibility Criteria:
Inclusion Criteria:

* Have a diagnosis of Acute Myelogenous Leukemia (AML) according to World Health Organization (WHO) classification
* Relapsed after receiving up to 2 prior induction regimens (i.e. first or second relapse)or are refractory to not more than one prior combination chemotherapy induction regimen
* Be ≥ 55 years of age
* Have an Eastern Cooperative Oncology Group (ECOG) score of 0-2
* Be able to comply with study procedures and follow-up examinations
* Be nonfertile or agree to use birth control during the study through the end of treatment visit and for at least 90 days after the last dose of study drug
* Have adequate liver and renal function as indicated by certain laboratory values

Exclusion Criteria:

* Received previous treatment with clofarabine
* Received bolus, intermediate or high-dose cytarabine as induction therapy unless certain remission criteria are met
* Have received a hematopoietic stem cell transplant (HSCT) within the previous 3 months
* Have moderate or severe graft versus host disease (GVHD), whether acute or chronic
* Are receiving any other chemotherapy or investigational therapy. Patients must have been off prior AML therapy for at least 2-6 weeks prior to entering study.
* Have a psychiatric disorder that would interfere with consent, study participation, or follow-up
* Have an active, uncontrolled infection
* Have any other severe concurrent disease, or have a history of serious organ dysfunction or disease involving the heart, kidney, liver, or other organ system
* Have been diagnosed with another malignancy, unless disease-free for at least 5 years; patients with treated nonmelanoma skin cancer, in situ carcinoma, or cervical intraepithelial neoplasia, regardless of the disease-free duration, are eligible for this study if definitive treatment for the condition has been completed; patients with organ-confined prostate cancer with no evidence of recurrent or progressive disease are eligible if hormonal therapy has been initiated or the malignancy has been surgically removed.
* Have clinical evidence suggestive of central nervous system (CNS) involvement with leukemia unless lumbar puncture confirms absence of leukemic blasts in the cerebrospinal fluid(CSF)
* Known HIV positivity
* Are pregnant or lactating