Session: 614. Acute Lymphoblastic Leukemias: Therapies, Excluding Transplantation and Cellular Immunotherapies II
Hematology Disease Topics & Pathways:
Lymphoid Leukemias, Fundamental Science, Non-Biological, Chemotherapy, Lymphoid Leukemias, Clinically Relevant, Diseases, Therapies, Lymphoid Malignancies
Firstly, B-ALL cell lines (IKZF1del: MUTZ-5, MHH-CALL-4; IKZF1wt: NALM6) and primary patient samples (n=10, 5 with IKZF1del and 5 with IKZF1wt) were treated with different HDACi, including valproic acid, vorinostat, romidepsin, RGFP966 and a novel HDAC-selective inhibitor tucidinostat. But noteworthily, only tucidinostat yielded specific and selective proliferation inhibition in IKZF1del cell line(IC50=1.377±0.05) and IKZF1del patients samples (IC50=2.318±0.07), compared with the effect on IKZF1wt cells. Interestingly, tucidinostat induced remarked increase of mRNA and protein of IKZF1 expression in leukemia bulk and IKZF1del single cell. Seahorse metabolic flux assay, lactate and ATP measurements was performed and revealed that tucidinostat treatment reduced glycolysis (P=0.0067), lactic acid (P＜0.0001) and ATP level (P＜0.0001) in IKZF1del B-ALL cell lines. To verify metabolic change is depend on IKZF1 induction or not,dominant-negative Ikaros isoform 6 (DN-IK6), deletion of exons 4-7, was transfected into IKZF1wt Nalm-6 cell line to negative regulate of IKZF1 wide-type expression. Overexpression of DN-IK6 in Nalm-6, increases sensitivity to tucidinostat, glycolytic capacity(p=0.05) and glycolytic reserve (p=0.012) also increases. While tucidinostat treating with the IK6-Nalm-6, tucidinostat would restore the transcriptional repressor function of the remaining wild-type IKZF1 allele and decrease glycolytic capacity(p=0.011) and glycolytic reserve(p=0.014). Notably, the metabolic rate-limiting enzymes HK2 and PKM2 were strongly repressed. These data indicate that tucidinostat reverses the metabolic reprogramming of glycolysis or Warburg effect in IKZF1del B-ALL in an IKZF1-inducing dependent manner. For in vivo study, PDX model with immunodeficient NOD/SCID/IL2Rgnull mice were injected with heavily-treated refractory/relapsed IKZF1del B-ALL patient samples (n=2) and treated with tucidinostat with different dosage of 5-12.5mg/kg/day. Administration of tucidinostat observed IKAROS expression trajectory and resulted in prolonged animal survival in IKZF1del B-ALL PDX model（P＜0.0001). Secondary transplantation of ALL cells from tucidinostat or vehicle-treated (1 x106) recipients revealed significantly improved survival in tucidinostat -treated group (p= 0.0235). These results indicate that tucidinostat treatment might elimination leukemia-initiating cells.Additionally, to profile the IKZF1del B-ALL chromatin accessibility changes after tucidinostat-treatment. We performed ATAC-seq and observed a clear increase in accessibility at TCA cycle related gene and decrease in accessibility at glycolysis related gene.Furthermore, tucidinostat, formerly known as chidamide, was added to an open-label, one-arm PDT-Ph-like-ALL trial targeting adult Ph-like ALL, which is characterized with high frequency in IKZF1 deletions (Clinicaltrials.gov. NCT03564470). Preliminary data of PDT-Ph-like-ALL indicate that tucidinostat was effective and well-tolerated, yielded promising response in IKZF1del Ph-like ALL (ASH2018, poster 4011; EHA 2019, PF181).
Collectively, our study demonstrates that the novel HDAC-selective inhibitor, tucidinostat, could specifically target IKZF1del high-risk B-ALL, by restoring the IKZF1 expression, resulting in attenuation of proliferation, reverse the Warburg effect and improvement of the survival in PDX model and preliminary data in clinical trial. These findings provide mechanistic insights and a promising therapeutic strategy for IKZF1 haploinsufficiency alterations B-ALL patients.
Disclosures: No relevant conflicts of interest to declare.
See more of: Oral and Poster Abstracts