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Enasidenib induces acute myeloid leukemia cell differentiation to promote clinical response.

ABSTRACT: Recurrent mutations at R140 and R172 in isocitrate dehydrogenase 2 (IDH2) occur in many cancers, including ∼12% of acute myeloid leukemia (AML). In preclinical models these mutations cause accumulation of the oncogenic metabolite R-2-hydroxyglutarate (2-HG) and induce hematopoietic differentiation block. Single-agent enasidenib (AG-221/CC-90007), a selective mutant IDH2 (mIDH2) inhibitor, produced an overall response rate of 40.3% in relapsed/refractory AML (rrAML) patients with mIDH2 in a phase 1 trial. However, its mechanism of action and biomarkers associated with response remain unclear. Here, we measured 2-HG, mIDH2 allele burden, and co-occurring somatic mutations in sequential patient samples from the clinical trial and correlated these with clinical response. Furthermore, we used flow cytometry to assess inhibition of mIDH2 on hematopoietic differentiation. We observed potent 2-HG suppression in both R140 and R172 mIDH2 AML subtypes, with different kinetics, which preceded clinical response. Suppression of 2-HG alone did not predict response, because most nonresponding patients also exhibited 2-HG suppression. Complete remission (CR) with persistence of mIDH2 and normalization of hematopoietic stem and progenitor compartments with emergence of functional mIDH2 neutrophils were observed. In a subset of CR patients, mIDH2 allele burden was reduced and remained undetectable with response. Co-occurring mutations in NRAS and other MAPK pathway effectors were enriched in nonresponding patients, consistent with RAS signaling contributing to primary therapeutic resistance. Together, these data support differentiation as the main mechanism of enasidenib efficacy in relapsed/refractory AML patients and provide insight into resistance mechanisms to inform future mechanism-based combination treatment studies.

SUBMITTER: Amatangelo MD

PROVIDER: S-EPMC5553578 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:Recurrent mutations affecting cellular metabolism and epigenetic regulation are implicated in the pathogenesis of acute myeloid leukemia (AML). Isocitrate dehydrogenase 2 (IDH2) gene mutations are described in 12% of patients with AML and 5% of patients with myelodysplastic syndromes. IDH2 enzyme is involved in the Krebs cycle, catalyzing ?-ketoglutarate from isocitrate. Mutant IDH2 enzymes acquire a neomorphic enzymatic activity with the ability to produce 2-hydroxyglutarate from ?-ketoglutarate, inhibiting multiple ?-ketoglutarate-dependent dioxygenase reactions; leading to aberrant DNA hypermethylation and differentiation block in myeloid precursors and ultimately promoting leukemogenesis. Enasidenib (formerly AG-221) is an oral small molecule selective targeted inhibitor of the mutant IDH2 enzyme, approved in August 2017 by the United States Food and Drug Administration for the treatment of patients with relapsed or refractory (R/R) IDH2-mutated AML. Preclinical studies showed the effectiveness of enasidenib in inhibiting the production of 2-hydroxyglutarate with high potency, and alleviating the mutant IDH2-induced differentiation block. In the original AG221-001 phase I/II trial, patients with R/R AML were treated with enasidenib single agent therapy at escalating doses up to 650 mg daily, with the 100 mg dose level identified to be safe and effective for further evaluation. Overall, 113 patients were treated in the dose-escalation and 126 in the dose-expansion cohorts. The overall response rate for R/R patients was 40%, including a complete remission of 19%. At a median follow up of 7.7 months, the median overall survival was 9.3 months, and reached 19.7 months in responders. Enasidenib was well tolerated, although adverse events of clinical interest include indirect hyperbilirubinemia and IDH-inhibitor-induced differentiation syndrome, which can be life threatening if not identified and treated promptly. Ongoing clinical trials evaluating enasidenib in combination with intensive chemotherapy and hypomethylating agents in newly diagnosed AML, and in rational combinations for R/R AML patients are underway.

Project description:A cute myeloid leukemia is a malignant disease of immature myeloid cells. Despite significant therapeutic effects of differentiation-inducing agents in some acute myeloid leukemia subtypes, the disease remains incurable in a large fraction of patients. Here we show that SK053, a thioredoxin inhibitor, induces differentiation and cell death of acute myeloid leukemia cells. Considering that thioredoxin knock-down with short hairpin RNA failed to exert antiproliferative effects in one of the acute myeloid leukemia cell lines, we used a biotin affinity probe-labeling approach to identify potential molecular targets for the effects of SK053. Mass spectrometry of proteins precipitated from acute myeloid leukemia cells incubated with biotinylated SK053 used as a bait revealed protein disulfide isomerase as a potential binding partner for the compound. Biochemical, enzymatic and functional assays using fluorescence lifetime imaging confirmed that SK053 binds to and inhibits the activity of protein disulfide isomerase. Protein disulfide isomerase knockdown with short hairpin RNA was associated with inhibition of cell growth, increased CCAAT enhancer-binding protein α levels, and induction of differentiation of HL-60 cells. Molecular dynamics simulation followed by the covalent docking indicated that SK053 binds to the fourth thioredoxin-like domain of protein disulfide isomerase. Differentiation of myeloid precursor cells requires the activity of CCAAT enhancer-binding protein α, the function of which is impaired in acute myeloid leukemia cells through various mechanisms, including translational block by protein disulfide isomerase. SK053 increased the levels of CCAAT enhancer-binding protein α and upregulated mRNA levels for differentiation-associated genes. Finally, SK053 decreased the survival of blasts and increased the percentage of cells expressing the maturation-associated CD11b marker in primary cells isolated from bone marrow or peripheral blood of patients with acute myeloid leukemia. Collectively, these results provide a proof-of-concept that protein disulfide isomerase inhibition has potential as a therapeutic strategy for the treatment of acute myeloid leukemia and for the development of small-molecule inhibitors of protein disulfide isomerase.

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Enasidenib induces acute myeloid leukemia cell differentiation to promote clinical response.

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