Background: Alterations in epigenetic control can cause defective post-translational histone modification and dysregulation of gene activity leading to cancer development. Overexpression of KDM4, a demethylase of histone lysine 9 methyl 2/3 and lysine 36 methyl 2/3 (H3K9me2/3 and H3K36me2/3), is documented in a variety of cancers and is linked to aggressive disease and poor clinical outcomes. TACH101 is a novel first-in-class, selective and potent pan KDM4 inhibitor with favorable pharmacologic properties.

Methods: TACH101 was evaluated using in vitro and in vivo studies including cell-proliferation assays in multiple cancer cell lines and patient-derived organoid models, apoptotic and cell cycle analyses, pharmacology studies in various animal species, and efficacy studies in xenograft tumor models.

Results: Inhibition mechanism studies demonstrated TACH101 to be a reversible, α-ketoglutarate competitive, selective and potent inhibitor of KDM4 isoforms A-D with IC50 values less than 0.100 μM for all four isoforms. In vitro, TACH101 demonstrated potent increase of H3K36me3 levels (EC50 <0.001 μM, HTRF) in KYSE-150 cell line engineered to overexpress KDM4C and showed potent anti-proliferative activity in multiple cell lines in OncoPanel. Sub-micromolar levels of 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. TACH101 effects on cell cycle demonstrated a dose-dependent increase in the proportion of cells in S-phase at 24 and 48 hours relative to control: TACH101 at 0.01 μM concentration yielded fold increase of 1.7 and 2.1, and at 0.1 μM concentration yielded fold increase of 2.1 and 3.2. In vivo, TACH101 triggered effective tumor growth control in xenograft models including colorectal, esophageal, gastric, breast, and lymphoma with tumor growth inhibition of up to 100%. Flow cytometric analysis performed on single cells isolated from vehicle and TACH101-treated tumors showed a significant 2.5-fold reduction in population of tumorigenic cells (CD44high; EpCAM+) compared to vehicle control, indicating TACH101 may prevent self-renewal of cancer stem cells. This was corroborated in a study evaluating TACH101 effects on tumor initiating cell (TIC) frequency in colorectal tumors where TACH101 treatment reduced TIC frequency by 4.4-fold. Pharmacologic studies showed plasma protein binding of TACH101 to be ≥99% bound in mouse, rat, dog, and human. PK studies showed TACH101 exhibited low clearance, moderate volume of distribution, and good oral bioavailability in mouse, rat, and dog. Moreover, treatment with TACH101 resulted in little or no inhibitory effects on CYP enzyme activities.

Conclusions: TACH101 is a potent pan inhibitor of KDM4 that is suggestive of broad potential in cancer treatment. Further preclinical evaluation is ongoing to advance the molecule into clinical trials.

Citation Format: Sanghee Yoo, Chandtip Chandhasin, Joselyn R. Del Rosario, Young K. Chen, Jeff Stafford, Stephen Quake, Frank Perabo, Michael F. Clarke. TACH101, a first-in-class pan inhibitor of KDM4 histone lysine demethylases [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 2128.