3105 Background: The KDM4 family of histone lysine demethylases consists of four main isoforms (KDM4A, B, C, D), all of which have been identified as key oncogenic drivers. They function as epigenetic regulators and control transitions between transcriptionally silent and active chromatin states via removal of methyl marks on histone H3K9 and histone H3K36. KDM4 isoforms play an important role in the epigenetic dysregulation in various cancers and is linked to more aggressive disease and poorer clinical outcomes. Functional redundancy and cross-activity have been observed across KDM4 family members, thus, selective inhibition of one isoform appears to not be effective. TACH101 is a novel, first-in-class pan inhibitor of KDM4 that simultaneously targets multiple isoforms of KDM4. Here we present data that show TACH101 has promising pre-clinical and pharmacologic properties as a cancer therapeutic. Methods: TACH101 was evaluated in in vitro and in vivo studies including cell-proliferation assays in multiple cancer cell lines, apoptotic and cell cycle analyses, and efficacy studies in various xenograft tumor models and patient-derived organoid models. Results: In vitro, TACH101 was broadly effective in killing 67% (200 out of 300) of cancer cell lines screened. TACH101 demonstrated potent increase of H3K36me3 levels (EC50 < 0.001 mM, HTRF) in KYSE-150 cell line engineered to overexpress KDM4C and potent anti-proliferative activity in multiple cell lines in OncoPanel. TACH101 treatment increased cancer cell population in S-phase in multiple cancer cell lines indicating cell-cycle arrest. TACH101 induced apoptosis in human colorectal (HT-29), esophageal (KYSE-150), and triple negative breast cancer (MDA-MB-231) cell lines with EC50s ranging from 0.033-0.092 µM. In vivo, TACH101 triggered effective tumor control in xenograft models including colorectal, esophageal, gastric, breast, and lymphoma with tumor growth inhibition of up to 100%. Further evaluation using a panel of patient-derived colorectal models and patient-derived organoids showed a strong correlation of TACH101 sensitivity with MSI-H status (IC50 ranges 1-150 nM). TACH101 also reduced tumorigenic potential by 4.4-fold as determined by FACS analysis using sorted CD44High EpCAM+ population in Limiting Dilution Assays in vivo, suggesting that reduction of cancer stem cells by TACH101 may be effective in therapy-resistant settings. Pharmacologic studies showed TACH101 demonstrated favorable cell permeability, good oral bioavailability, and high metabolic stability. Conclusions: Extensive preclinical work on TACH101 KDM4 inhibitor shows compelling data and broad applicability as a potential anti-cancer agent. Further evaluation is ongoing to advance the molecule into clinical trials.
EXTH-69. INCREASED CANCER CELL PERMEABILITY FOLLOWING TUMOR TREATING FIELDS (TTFIELDS) APPLICATION IN VITRO
