Targeted therapy of AML1-ETO positive acute myeloid leukemia with histone deacetylase inhibitors

In t(8;21) acute myeloid leukaemia (AML), the leukemogenesis is supposed to be promoted by interference with expression of AML1 target genes. Repressor complex associated with AML1-ETO fusion protein recruits class I histone deacetylases (HDAC). Valproic acid (VPA) was found to have an extensive effect on AML blasts, via inhibition of class I HDAC. We aimed to characterize the differentiation effect of VPA on AML1-ETO-positive leukemic cells and to determine the expression pattern of AML1 target genes. Kasumi-1 (M2 AML1-ETO-positive), Kasumi-6 (M2 AML1-ETO- negative), MV4-11 (MLL-AF4-positive) and K562 cells were treated with VPA and 12-0-tetra- decanoylphorbol-13-acetate (TPA) and examined by flow cytometry and qRT-PCR. Two AML1-ETO- positive and two negative patients' bone marrow diagnostic samples were treated with VPA and TPA to confirm in vitro findings. Valproic acid induced apoptosis in AML1-ETO-positive and MLL- AF4-positive cells in dose dependent manner. But changes of immunophenotype proving the differentiation were observed purely in AML1-ETO-positive cell line (decreased CD33/34/117 and increased CD11a/11b expression). However, differentiated cells exhibited positivity of AnnexinV; hence the relationship between cell death and differentiation had to be evaluated. Apoptosis was blocked by..

Targeted therapy of AML1-ETO positive acute myeloid leukemia with histone deacetylase inhibitors

In t(8;21) acute myeloid leukaemia (AML), the leukemogenesis is supposed to be promoted by interference with expression of AML1 target genes. Repressor complex associated with AML1-ETO fusion protein recruits class I histone deacetylases (HDAC). Valproic acid (VPA) was found to have an extensive effect on AML blasts, via inhibition of class I HDAC. We aimed to characterize the differentiation effect of VPA on AML1-ETO-positive leukemic cells and to determine the expression pattern of AML1 target genes. Kasumi-1 (M2 AML1-ETO-positive), Kasumi-6 (M2 AML1-ETO- negative), MV4-11 (MLL-AF4-positive) and K562 cells were treated with VPA and 12-0-tetra- decanoylphorbol-13-acetate (TPA) and examined by flow cytometry and qRT-PCR. Two AML1-ETO- positive and two negative patients' bone marrow diagnostic samples were treated with VPA and TPA to confirm in vitro findings. Valproic acid induced apoptosis in AML1-ETO-positive and MLL- AF4-positive cells in dose dependent manner. But changes of immunophenotype proving the differentiation were observed purely in AML1-ETO-positive cell line (decreased CD33/34/117 and increased CD11a/11b expression). However, differentiated cells exhibited positivity of AnnexinV; hence the relationship between cell death and differentiation had to be evaluated. Apoptosis was blocked by..

Original Article Experimental Therapy with 9-[2-(Phosphonomethoxy)ethyl]- 2,6-diaminopurine (PMEDAP): Origin of Resistance (MRP4 / MRP5 / PMEDAP resistance)

Abbreviations: DTX -docetaxel, MRP (1-5) -multiple drug resistance protein, PMEA -9-[2-(phosphonomethoxy)ethyl]adenine, PMEDAP -9-[2-(phosphonomethoxy)ethyl]-2,6-diaminopurine, RQ-RT-PCR -real-time quantitative reverse transcriptasepolymerase chain reaction, SD/Cub -Sprague-Dawley inbred rats/Charles University Biology. Abstract. The role of MRP4 and MRP5 transporters in the acyclic nucleoside phosphonate PMEDAP efflux was studied in vitro (CCRF-CEM cells) and in vivo (spontaneous transplantable T-cell lymphoma of SD/Cub inbred rats). The increased resistance against the cytostatic agent PMEDAP during longterm treatment was found to be associated with overexpression of MRP4 and MRP5 genes. The course of both gene activation differs significantly. While the MRP5 function is important in the onset of PMEDAP resistance, the intensity of the relative MRP4 gene expression increases rather continuously. Our data indicate cooperative acting of both MRP4 and MRP5 genes during the PMEDAP resistance development

LOGGIC/FIREFLY-2: a phase 3, randomized trial of tovorafenib vs. chemotherapy in pediatric and young adult patients with newly diagnosed low-grade glioma harboring an activating RAF alteration

Abstract Background Pediatric low-grade glioma (pLGG) is essentially a single pathway disease, with most tumors driven by genomic alterations affecting the mitogen-activated protein kinase/ERK (MAPK) pathway, predominantly KIAA1549::BRAF fusions and BRAF V600E mutations. This makes pLGG an ideal candidate for MAPK pathway-targeted treatments. The type I BRAF inhibitor, dabrafenib, in combination with the MEK inhibitor, trametinib, has been approved by the United States Food and Drug Administration for the systemic treatment of BRAF V600E-mutated pLGG. However, this combination is not approved for the treatment of patients with tumors harboring BRAF fusions as type I RAF inhibitors are ineffective in this setting and may paradoxically enhance tumor growth. The type II RAF inhibitor, tovorafenib (formerly DAY101, TAK-580, MLN2480), has shown promising activity and good tolerability in patients with BRAF-altered pLGG in the phase 2 FIREFLY-1 study, with an objective response rate (ORR) per Response Assessment in Neuro-Oncology high-grade glioma (RANO-HGG) criteria of 67%. Tumor response was independent of histologic subtype, BRAF alteration type (fusion vs. mutation), number of prior lines of therapy, and prior MAPK-pathway inhibitor use. Methods LOGGIC/FIREFLY-2 is a two-arm, randomized, open-label, multicenter, global, phase 3 trial to evaluate the efficacy, safety, and tolerability of tovorafenib monotherapy vs. current standard of care (SoC) chemotherapy in patients < 25 years of age with pLGG harboring an activating RAF alteration who require first-line systemic therapy. Patients are randomized 1:1 to either tovorafenib, administered once weekly at 420 mg/m2 (not to exceed 600 mg), or investigator’s choice of prespecified SoC chemotherapy regimens. The primary objective is to compare ORR between the two treatment arms, as assessed by independent review per RANO-LGG criteria. Secondary objectives include comparisons of progression-free survival, duration of response, safety, neurologic function, and clinical benefit rate. Discussion The promising tovorafenib activity data, CNS-penetration properties, strong scientific rationale combined with the manageable tolerability and safety profile seen in patients with pLGG led to the SIOPe-BTG-LGG working group to nominate tovorafenib for comparison with SoC chemotherapy in this first-line phase 3 trial. The efficacy, safety, and functional response data generated from the trial may define a new SoC treatment for newly diagnosed pLGG. Trial registration ClinicalTrials.gov: NCT05566795. Registered on October 4, 2022