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Clofarabine is a second-generation purine nucleoside analog that has been synthesized to overcome the limitations and incorporate the best qualities of fludarabine and cladribine. Clofarabine acts by inhibiting ribonucleotide reductase and DNA polymerase, thereby depleting the amount of intracellular deoxynucleoside triphosphates available for DNA replication. Compared to its precursors, clofarabine has an increased resistance to deamination and phosphorolysis, and hence better stability as well as higher affinity to deoxycytidine kinase (dCyd), the rate-limiting step in nucleoside phosphorylation. Since the initiation of the first phase I study of clofarabine in 1993 in patients with hematologic and solid malignancies, clofarabine has demonstrated single-agent antitumor activity in adult acute leukemia, including acute myeloid leukemia (AML). Due to its unique properties of biochemical modulation when used in combination with other chemotherapy drugs, mainly cytarabine, combination regimens containing clofarabine have been evaluated. A review of the English literature was performed that included original articles and related reviews from the MEDLINE (PubMed) database and from abstracts based on the publication of meeting materials. This review describes the development, pharmacology and clinical activity of clofarabine, as well as its emerging role in the treatment of adult patients with AML and myelodysplastic syndrome.

Purpose Outcomes of patients with acute myeloid leukemia (AML) who are refractory to high-dose Cytarabine (HiDAC)-based induction are dismal. Allogeneic hematopoietic stem cell transplantation (AHSCT) as initial salvage may be effective and potentially superior to conventional salvage chemotherapy. Methods Eighteen percent (285 of 1597) of AML patients were primary refractory to HiDAC-based regimens at the MD Anderson Cancer Center between 1995 and 2009. AHSCT was the initial salvage in 28 cases. These patients were compared against 149 patients who received salvage chemotherapy, but never received AHSCT. Results Patients receiving salvage chemotherapy were older, had higher bone marrow blasts percentage, and higher incidence of unfavorable cytogenetics (P<0.001). Median time from induction to AHSCT was 76 days. Objective response was achieved in 23 of 28 patients (82%) undergoing AHSCT. The incidence of grade III/IV acute and chronic graft versus-host-disease was 11% and 29%, respectively. Median follow up for living patients is 80 months. Median overall survival (OS) was 15.7 months and 2.9 months for AHSCT and chemotherapy, respectively (P<0.001); the 3-year OS rates were 39% and 2%, respectively. ASHCT as initial salvage therapy was identified as an independent prognostic factor for survival in multivariate analysis (HR = 3.03; P < 0.001). Conclusion Initial salvage therapy with AHSCT in patients with primary HiDAC refractory AML is feasible and may yield superior outcomes to salvage chemotherapy.

Clofarabine is a second-generation purine nucleoside analogue that has been synthesized to overcome the limitations and incorporate the best qualities of fludarabine and cladribine. Clofarabine acts by inhibiting ribonucleotide reductase and DNA polymerase, thereby depleting the amount of intracellular deoxynucleoside triphosphates available for DNA replication. Compared with its precursors, clofarabine has an increased resistance to deamination and phosphorolysis, hence better stability, as well as higher affinity to deoxycytidine kinase (dCyd), the rate-limiting step in nucleoside phosphorylation. In 1993, the first Phase I study was initiated in patients with hematologic and solid malignancies. Since then, clofarabine has demonstrated single-agent antitumor activity in pediatric and adult acute leukemia. Owing to its unique properties of biochemical modulation when used in combination with other established antileukemic drugs, mainly cytarabine, combination regimens containing clofarabine are being evaluated. A review of the English literature was performed that included original articles and related reviews from the MEDLINE (PubMed) database and from abstracts based on the publication of meeting materials. This article describes the development, pharmacology and clinical activity of clofarabine, as well as its emerging role in the treatment of acute leukemia, myelodysplastic syndrome and solid tumors.

Acute myelogenous leukemia (AML) is a genetically heterogeneous disease in which somatic mutations, that disturb cellular growth, proliferation, and differentiation, accumulate in hematopoietic progenitor cells. Cytogenetic findings, at diagnosis, have been proven to be one of the most important prognostic indicators in AML. About half of the patients with AML are found to have “normal” cytogenetic analysis by standard culture techniques. These patients are considered as an intermediate risk group. Cytogenetically normal AML (CN‐AML) is the largest cytogenetic risk group, and the variation in clinical outcome of patients in this group is greater than in any other cytogenetic group. Besides mutation testing, age and presenting white blood cell count are important predictors of overall survival, suggesting that other factors independent of cytogenetic abnormalities, contribute to the outcome of patients with AML. The expanding knowledge at the genetic and molecular levels is helping define several subgroups of patients with CN‐AML with variable prognosis. In this review, we describe the clinical and prognostic characteristics of CN‐AML patients as a group, as well as the various molecular and genetic aberrations detected in these patients and their clinical and prognostic implications. Am. J. Hematol., 2012. © 2011 Wiley Periodicals, Inc.