Top advances of the year: Myeloproliferative neoplasms

The rapid pace of drug development in hematology has led to multiple approvals for myelofibrosis (MF) and polycythemia vera (PV) in recent years. Moreover, there are many innovative agents and combinations being explored for myeloproliferative neoplasms (MPNs). In the past year, there have been several advances in MF, PV, and essential thrombocythemia. In MF, investigational approaches are focusing on strategies to optimize inhibition of signal transduction (including JAK inhibition), modify epigenetics, enhance apoptosis, target DNA replication, transform host immunity, and/or alter the tumor microenvironment. In PV, ropeginterferon alfa-2b has been introduced to the market in the United States, and data continue to accumulate to support the safety and efficacy of this treatment. Hepcidin mimesis is also emerging as a novel way to treat erythrocytosis. In essential thrombocythemia, ropeginterferon alfa-2b is being evaluated, as are therapies to modify epigenetics and inhibit CALR. The enhanced focus on MPNs brings hope that our field can improve morbidity and mortality in this group of diseases.

SWOG 1318: A Phase II Trial of Blinatumomab Followed by POMP Maintenance in Older Patients With Newly Diagnosed Philadelphia Chromosome-Negative B-Cell Acute Lymphoblastic Leukemia

PURPOSE

Chemotherapy outcomes in older patients with Philadelphia (Ph) chromosome-negative B-acute lymphoblastic leukemia (ALL) are very poor. Here, we evaluated blinatumomab as induction and consolidation therapy followed by prednisone, vincristine, 6-mercaptopurine, and methotrexate (POMP) maintenance chemotherapy in this patient population.

PATIENTS AND METHODS

Patients were treated at National Clinical Trial Network sites. Eligibility criteria included age ≥ 65 years and newly diagnosed Ph chromosome-negative B-ALL. Patients received blinatumomab as induction for one-two cycles until attainment of response (complete remission (CR) and CR with incomplete count recovery). Patients then received three cycles of consolidation with blinatumomab followed by 18 months of POMP maintenance chemotherapy. Eight doses of intrathecal methotrexate were administered as central nervous system prophylaxis.

RESULTS

Twenty-nine eligible patients were enrolled. The median age was 75 years, and the median bone marrow blast count at diagnosis was 87%. Cytogenetic risk was poor in 10 patients (34%), and five of 14 patients (36%) tested had the Ph-like ALL gene signature. Nineteen patients (66%; 95% CI, 46 to 82) achieved CR. Kaplan-Meier 3-year disease-free survival and overall survival estimates were 37% (95% CI, 17 to 57) and 37% (95% CI, 20 to 55), respectively.

CONCLUSION

Blinatumomab was well tolerated and effective in the treatment of older patients with newly diagnosed Ph chromosome-negative B-ALL, including patients with poor-risk cytogenetics. The 3-year disease-free survival and overall survival results are encouraging and suggest that this approach should be further explored.

Phase II trial of cytarabine and mitoxantrone with devimistat in acute myeloid leukemia

Devimistat is a TCA cycle inhibitor. A previously completed phase I study of devimistat in combination with cytarabine and mitoxantrone in patients with relapsed or refractory AML showed promising response rates. Here we report the results of a single arm phase II study (NCT02484391). The primary outcome of feasibility of maintenance devimistat following induction and consolidation with devimistat in combination with high dose cytarabine and mitoxantrone was not met, as maintenance devimistat was only administered in 2 of 21 responders. The secondary outcomes of response (CR + CRi) and median survival were 44% (21/48) and 5.9 months respectively. There were no unexpected toxicities observed. An unplanned, post-hoc analysis of the phase I and II datasets suggests a trend of a dose response in older but not younger patients. RNA sequencing data from patient samples reveals an age-related decline in mitochondrial gene sets. Devimistat impairs ATP synthesis and we find a correlation between mitochondrial membrane potential and sensitivity to chemotherapy. Devimistat also induces mitochondrial reactive oxygen species and turnover consistent with mitophagy. We find that pharmacological or genetic inhibition of mitochondrial fission or autophagy sensitizes cells to devimistat. These findings suggest that an age related decline in mitochondrial quality and autophagy may be associated with response to devimistat however this needs to be confirmed in larger cohorts with proper trial design.

Combining cytarabine and mitoxantrone with the tricarboxylic acid cycle inhibitor devimistat has been reported in a phase I clinical trial with relapsed or refractory acute myeloid leukaemia (AML). Here, the authors report the outcomes of a phase II study, analyse samples from both phases and perform preclinical analyses that show mitochondrial fission or autophagy inhibition sensitizes AML cells to devimistat.

Efficacy of 10-day decitabine in acute myeloid leukemia

The azanucleotide decitabine is used in the treatment of acute myeloid leukemia (AML). Studies have shown conflicting results with 10-day regimens used in previously untreated AML patients. Additionally, there is little data on 10-day decitabine regimens in the relapsed setting. This study investigated outcomes of 108 adult patients with AML in the upfront and relapsed setting treated with a 10-day decitabine regimen. In the upfront group, the overall response rate (ORR, CR + CRi) was 36.1% and the median overall survival (OS) was 6.6 months, while the relapsed/refractory group had an ORR of 25% with an OS of 4.8 months. When analyzed with respect to cytogenetics, the upfront group featured an ORR of 28.1% with an OS of 9.4 months in the intermediate cytogenetic cohort compared to a 40.5% ORR and an OS of 5.4 months in the unfavorable cytogenetic cohort. An analysis of the relapsed/refractory group demonstrated an ORR of 26.3% with an OS of 7.9 months for intermediate cytogenetics versus 25.0% with an OS of 1.8 months in the unfavorable cohort. While these response rates are similar to previously published data, the median OS appears shorter.

Prostaglandin E1 and Its Analog Misoprostol Inhibit Human CML Stem Cell Self-Renewal via EP4 Receptor Activation and Repression of AP-1

Effective treatment of chronic myelogenous leukemia (CML) largely depends on the eradication of CML leukemic stem cells (LSCs). We recently showed that CML LSCs depend on Tcf1 and Lef1 factors for self-renewal. Using a connectivity map, we identified prostaglandin E1 (PGE1) as a small molecule that partly elicited the gene expression changes in LSCs caused by Tcf1/Lef1 deficiency. Although it has little impact on normal hematopoiesis, we found that PGE1 treatment impaired the persistence and activity of LSCs in a pre-clinical murine CML model and a xenograft model of transplanted CML patient CD34⁺ stem/progenitor cells. Mechanistically, PGE1 acted on the EP4 receptor and repressed Fosb and Fos AP-1 factors in a β-catenin-independent manner. Misoprostol, an FDA-approved EP4 agonist, conferred similar protection against CML. These findings suggest that activation of this PGE1-EP4 pathway specifically targets CML LSCs and that the combination of PGE1/misoprostol with conventional tyrosine-kinase inhibitors could provide effective therapy for CML.