GLIX1: A first-in-class oral molecule targeting the DNA damage response by restoring TET2 activity.

e14072 Background: The Ten-Eleven Translocation methylcytosine dioxygenase 2 (TET2) initiates the DNA demethylation by oxidizing 5-methylcytosine to 5-hydroxymethylcytosine (5hmC), 5-formylcytosine and 5-carboxycytosine. The later two oxidized species are processed by base excision repair (BER) generating single-stranded DNA breaks that are well tolerated in normal cells. In cancer, DNA hypermethylation is common and TET2 activity is inhibited, giving rise to increased DNA methylation in close genomic proximity. Restoration of TET2 activity in cancer cells leads to excessive BER, resulting in numerous single-strand DNA breaks in close proximity, which ultimately converge to form lethal double-strand DNA breaks overwhelming DNA repair capacity, resulting in cell death. This mechanism is applicable to hematological and solid tumors and is particularly pronounced in glioblastoma (GBM). GLIX1 is a small molecule administered orally, targeting the DNA damage response by enhancing TET2 activity. Methods: Mechanistic studies evaluated the effect of GLIX1 on TET2 activity and 5hmC generation using biochemical assays, in vitro cellular systems, and in vivo models. Brain penetration of GLIX1 was assessed in rodents following oral administration with determination of brain-to-plasma exposure ratios. Antitumor activity was evaluated in multiple subcutaneous and orthotopic GBM xenograft models (U87-MG and SNB-19). Safety was evaluated in repeat-dose toxicology studies in rats and dogs. Results: GLIX1 increased TET2-dependent 5hmC generation in biochemical assays, in vitro, and in vivo systems. High potency of GLIX1 was observed in vitro in a broad range of cancer cell lines. GLIX1 demonstrated robust brain penetration, with brain exposure corresponding to 68–85% of plasma levels in mice following oral dosing. In GBM xenograft models, GLIX1 showed pronounced antitumor activity following oral administration. Toxicology studies demonstrated that GLIX1 is safe and well tolerated, up to the highest feasible doses tested (2000 mg/kg rats and 1000 mg/kg dogs). Conclusions: GLIX1 targets the DNA damage response by enhancing TET2 activity. Its unique mechanism is applicable to a broad range of cancers. GLIX1 crosses the blood brain barrier and has shown significant activity in various in vitro and in vivo GBM and glioma tumor models. These data, together with the fact that high grade gliomas are characterized by markedly reduced genomic levels of 5hmC compared with normal tissue, reflecting impaired TET2 activity and a potential therapeutic vulnerability, support clinical evaluation of GLIX1 in GBM as the first indication. A first-in-human Phase I clinical trial with GLIX1 in Adults with Recurrent or Progressive High-Grade Glioma is planned to initiate in Q1 2026.