P485: targeting histone lysine-specific demethylases by jib-04 improves response of aml cells to venetoclax treatment

Background: Acute myeloid leukemia (AML) is a heterogeneous, hematologic malignancy that is associated with a poor prognosis. Available treatment options are limited, especially for older patients and others who are ineligible for intensive chemotherapy. The BCL2-specific inhibitor venetoclax has proven efficacy in AML treatment particularly in combination with hypomethylating agents (HMA) or low-dose cytarabine. However, data from a clinical phase II study indicated a 30% failure rate after venetoclax+HMA treatment of newly diagnosed patients (PMID: 30361262), suggesting additional options are needed for patients who do not respond to available treatments or develop resistance. Compared to normal bone marrow histone lysine-specific demethylases are more highly expressed in AML, suggesting they are potential targets for therapeutic intervention. JIB-04 is a potent small molecule inhibitor for multiple members of the KDM 4, 5 and 6 families with KDM5A being the most sensitive. Combined pharmacological inhibition of KDM6 and KDM4 family members has been shown to reduce proliferation and increase apoptosis of primary AML cells of various subtypes (PMID: 29111428). Knockdown of KDM4 and KDM5 proteins leads to proliferation inhibition, cell cycle arrest, and apoptosis in AML cells (PMID: 34017391; PMID: 29602065). Together, these data highlight that KDM4, KDM5, and KDM6 proteins play an important role in the survival of AML cells. Aims: Describe the efficacy of JIB-04 alone and in combination with venetoclax for the treatment of AML. Identify the molecular changes due to JIB-04 in AML cells of varying genetic subtypes. Methods: We treated AML cell lines, patient AML blasts, and CD34+ cells from healthy donors with JIB-04, venetoclax, or the combination for 72 hours. Apoptosis was quantified by annexinV/propidium iodide staining. Cell proliferation of AML cell lines treated with JIB-04 was evaluated using MTT assay and transcriptome profiling was done by RNA-Seq. Results: Treatment of AML cell lines with low nanomolar doses (IC50 range from 8-60nM) of JIB-04 resulted in inhibition of proliferation and apoptosis. The combination of JIB-04 with venetoclax showed a strong synergistic effect in all AML cell lines including AML cell lines with relative resistance to venetoclax (Figure 1A). Moreover, patient AML blasts also showed a synergistic response to the drug combination compared to single-drug treatments (Figure 1B). In contrast, viability of normal CD34+ hematopoietic cells was not affected by JIB-04 treatment at a dose of 100nM that leads to apoptosis in AML cells, indicating a therapeutic window. Changes in the transcriptome after JIB-04 treatment were analyzed in AML-OCI3 and MOLM-13 cells. In both cell lines, genes related to the mTOR pathway and stress response were downregulated, indicating possible mechanisms reducing proliferation and increasing apoptosis. Further experiments will be performed to confirm the identified regulated genes as druggable targets in AML that improve venetoclax response. Image:Summary/Conclusion: While JIB-04 alone shows some anti-leukemic effect, this study highlights the potential therapeutic benefit of combining JIB-04 and venetoclax in AML. This novel drug combination synergistically inhibits cell growth and induces apoptosis in AML cells with various subtypes. In vivo studies are currently underway to show the efficacy of this drug combination in patient derived xenograft models.