Background: TACH101 is a novel, selective and potent inhibitor of KDM4 in development for advanced cancers. KDM4 plays a key role in epigenetic regulation by removing methyl marks on histone H3K9 and H3K36. Overexpression of KDM4 leads to dysregulation of transcription, cell cycle, and DNA replication/repair processes and has been associated with many cancer types. Methods: Candidate pharmacodynamic (PD) and sensitivity biomarkers for TACH101 were evaluated in vitro and in vivo using cancer cell lines, mouse xenograft models, gene microarrays, ChIP-seq, and ChIP-qPCR. Results: Evaluation of differential gene expression from tumor tissue identified several candidates as potential PD markers for TACH101 activity. In particular, direct binding of KDM4 to Protein Phosphatase 1 Regulatory subunit 10 (PPP1R10 or PNUTS) was confirmed by ChIP-seq in cell lines from esophageal (KYSE-150), breast (MDA-MB-231) and lymphoma (OCI-Ly19) cancers. TACH101 treatment caused 86% repression of PNUTS mRNA, as well as a 51% increase in H3K9me3, a mark of repressed transcription. A 78% decrease in H3K36me3 at the PNUTS gene was also observed. PNUTS as a target of KDM4 was validated via ChIP-qPCR in xenograft tumors of KYSE-150, OCI-Ly19 and SU-60 (colorectal). In vivo, maximum inhibition of PNUTS was reached at 8 hours post TACH101 administration, when TACH101 concentration was 100-200 nM in tumors. In addition, extensive bioinformatics analysis using >300 cancer cell lines showed that cell lines with MSI-high (MSI-H) status tended to be more sensitive to TACH101 in vitro. This association was found with other markers of MSI-H status such as MMR gene mutations, MLH1 methylation status, and overall mutation frequency. To further test this association, TACH101 was evaluated in a panel of patient-derived xenograft (PDX) and organoid models. The results showed a strong correlation of TACH101 sensitivity with MSI-H status (IC50 ranges 1-150 nM). Conclusions: Candidate PD biomarkers of TACH101 activity for clinical evaluation have been identified and further studies are ongoing to explore current and additional markers. In addition, MSI-H status was associated with increased sensitivity to TACH101, which may be useful for enriching for select patient populations in clinical studies.

Citation Format: Frank Perabo, Sanghee Yoo, Chandtip Chandhasin, Joselyn Del Rosario, Young K. Chen, Ellen Filvaroff, Jeffrey A. Stafford, Stephen Quake, Michael F. Clarke. Identification of pharmacodynamic and sensitivity biomarkers for TACH101, a pan-inhibitor of KDM4 histone lysine demethylase [abstract]. In: Proceedings of the AACR-NCI-EORTC Virtual International Conference on Molecular Targets and Cancer Therapeutics; 2021 Oct 7-10. Philadelphia (PA): AACR; Mol Cancer Ther 2021;20(12 Suppl):Abstract nr P086.