Phase 1 study of the histone deacetylase inhibitor entinostat plus clofarabine for poor-risk Philadelphia chromosome-negative (newly diagnosed older adults or adults with relapsed refractory disease) acute lymphoblastic leukemia or biphenotypic leukemia

Abstract

Purpose: Despite advances in immunotherapies, the prognosis for adults with Philadelphia chromosome-negative, newly diagnosed (ND) or relapsed/refractory (R/R) acute lymphoblastic leukemia/acute biphenotypic leukemia (ALL/ABL) remains poor. The benzamide derivative entinostat inhibits histone deacetylase and induces histone hyperacetylation. The purine nucleoside analogue clofarabine is FDA-approved for R/R ALL in children 1-21 years of age. Low doses of clofarabine have been reported to induce DNA hypomethylation. We conducted a phase 1 study of low dose clofarabine with escalating doses of entinostat in adults with ND or R/R ALL/ABL.

Experimental design: Adults ≥60 years with ND ALL/ABL or ≥21 years with R/R ALL/ABL received repeated cycles every 3 weeks of entinostat (4 mg, 6 mg or 8 mg orally days 1 and 8) and clofarabine (10 mg/m2/day IV for 5 days, days 3-7) (Arm A). Adults aged 40-59 years with ND ALL/ABL or age ≥21 years in first relapse received entinostat and clofarabine prior to traditional chemotherapy on day 11 (Arm B). Changes in DNA damage, global protein lysine acetylation, myeloid-derived suppressor cells and monocytes were measured in PBMCs before and during therapy.

Results: Twenty-eight patients were treated at three entinostat dose levels with the maximum administered dose being entinostat 8 mg. The regimen was well tolerated with infectious and metabolic derangements more common in the older population versus the younger cohort. There was no severe hyperglycemia and no peripheral neuropathy in this small study. There were 2 deaths (1 sepsis, 1 intracranial bleed). Overall response rate was 32 %; it was 50 % for ND ALL/ABL. Entinostat increased global protein acetylation and inhibited immunosuppressive monocyte subpopulations, while clofarabine induced DNA damage in all cell subsets examined.

Conclusion: Entinostat plus clofarabine appears to be tolerable and active in older adults with ND ALL/ABL, but less active in R/R patients. Further evaluation of this regimen in ND ALL/ABL appears warranted.

Trial registration: ClinicalTrials.gov NCT01132573.

Keywords: Acetylation; Acute lymphoblastic leukemia; Clofarabine; Entinostat; HDAC inhibition.

Copyright © 2021. Published by Elsevier Ltd.

Figures

Figure One:. Consort Diagram and Treatment/Lab Schema for Entinostat Clofarabine in Adults with Acute Leukemia.

Patients started at DL1. DLMinus1 was a dose de-escalation arm in case of toxicity. No patients required DLMinus1.

Figure 2.

Evaluation of DNA damage and acetylation status. γH2AX median fluorescence intensity (MFI) in the tumor cell population, (A) non-responders, (B) responders. Acetylated lysine median fluorescence intensity (MFI) in each PBMC immune subset; B cells (C), T cells (D), and NK cells (E). C1D1 pre=cycle 1 day 1 pre entinostat dosing, C1D1 2hr=cycle 1 day 1, 2 hours post entinostat dosing, C1D8 pre=cycle 1 day 8 pre entinostat dosing, C1D8 2hr=cycle 1 day 8, 2 hours post entinostat dosing.

Figure 3.

Changes induced in monocytic MDSCs. (A) Changes in the frequency of monocytic MDSCs among viable PBMCs, (B) Changes in CD40 expression (MFI) on monocytic MDSCs, (C) Fold change of monocytic MDSCs at C1D8 from C1D1 pre, (D) Fold change of CD40 expression on monocytic MDSCs at C1D8 from C1D1 pre. C1D1 pre=cycle 1 day 1 pre entinostat dosing, C1D1 2hr=cycle 1 day 1, 2 hours post entinostat dosing, C1D8 pre=cycle 1 day 8 pre entinostat dosing, C1D8 2hr=cycle 1 day 8, 2 hours post entinostat dosing. NR=nonresponder, CR=Complete response, PR=partial response and SD=stable disease, MDSC=myeloid-derived suppressor cell.

Figure 4.

Changes induced in monocytes. (A,B,C) Changes in the frequency of total monocytes (A), classical monocytes (B), nonclassical monocytes (C) among viable PBMCs and (D) HLA-DR expression (MFI) on nonclassical monocytes at C1D8. C1D1 pre=cycle 1 day 1 pre entinostat dosing, C1D1 2hr=cycle 1 day 1, 2 hours post entinostat dosing, C1D8 pre=cycle 1 day 8 pre entinostat dosing, C1D8 2hr=cycle 1 day 8, 2 hours post entinostat dosing.