Mitoxantrone, etoposide and cytarabine following epigenetic priming with decitabine in adults with relapsed/refractory acute myeloid leukemia or other high-grade myeloid neoplasms: a phase 1/2 study.

DNA methyltransferase inhibitors sensitize leukemia cells to chemotherapeutics. We therefore conducted a phase 1/2 study of mitoxantrone, etoposide and cytarabine following 'priming' with 5-10 days of decitabine (dec/MEC) in 52 adults (median age 55 (range: 19-72) years) with relapsed/refractory acute myeloid leukemia (AML) or other high-grade myeloid neoplasms. During dose escalation in cohorts of 6-12 patients, all dose levels were well tolerated. As response rates appeared similar with 7 and 10 days of decitabine, a 7-day course was defined as the recommended phase 2 dose (RP2D). Among 46 patients treated at/above the RP2D, 10 (22%) achieved a complete remission (CR), 8 without measurable residual disease; five additional patients achieved CR with incomplete platelet recovery, for an overall response rate of 33%. Seven patients (15%) died within 28 days of treatment initiation. Infection/neutropenic fever, nausea and mucositis were the most common adverse events. While the CR rate compared favorably to a matched historic control population (observed/expected CR ratio=1.77), CR rate and survival were similar to two contemporary salvage regimens used at our institution (G-CLAC (granulocyte colony-stimulating factor (G-CSF); clofarabine; cytarabine) and G-CLAM (G-CSF; cladribine; cytarabine; mitoxantrone)). Thus, while meeting the prespecified efficacy goal, we found no evidence that dec/MEC is substantially better than other cytarabine-based regimens currently used for relapsed/refractory AML.

Copy-neutral loss of heterozygosity is prevalent and a late event in the pathogenesis of FLT3/ITD AML.

Patients with high FLT3 internal tandem duplication allelic ratios (FLT3/ITD-ARs) have a poor prognosis. Single-nucleotide polymorphism/comparative genomic hybridization, single-cell PCR and colony-forming assays were used to evaluate genotypic evolution of high FLT3/ITD-ARs in 85 acute myeloid leukemia (AML) patients. Microarrays were used to examine molecular pathways disrupted in leukemic blasts with high FLT3/ITD-ARs. Copy-neutral loss of heterozygosity (CN-LOH) was identified at the FLT3 locus in diagnostic samples with high FLT3/ITD-ARs (N=11), but not in samples with low FLT3/ITD-ARs (N=24), FLT3-activating loop mutations (N=11) or wild-type FLT3 (N=39). Single-cell assays showed that homozygous FLT3/ITD genotype was present in subsets of leukemic blasts at diagnosis but became the dominant clone at relapse. Less differentiated CD34(+)/CD33(-) progenitor colonies were heterozygous for FLT3/ITD, whereas more differentiated CD34(+)/CD33(+) progenitor colonies were homozygous for FLT3/ITD. Expression profiling revealed that samples harboring high FLT3/ITD-ARs aberrantly expressed genes within the recombination/DNA repair pathway. Thus, the development of CN-LOH at the FLT3 locus, which results in high FLT3/ITD-ARs, likely represents a late genomic event that occurs after the acquisition of the FLT3/ITD. Although the etiology underlying the development of CN-LOH remains to be clarified, the disruption in recombination/DNA repair pathway, which is present before the development of LOH, may have a role.