A Phosphatidyl Conjugated Telomerase-Dependent Telomere-Targeting Nucleoside Demonstrates Colorectal Cancer Direct Killing and Immune Signaling

Telomerase and telomeres are crucial in cancer cell immortalization, making them key targets for anticancer therapies. Currently, 6-thio-dG combined with the anti-PD1 inhibitor Cemiplimab is under Phase 2 clinical investigation (NCT05208944) in NSCLC patients resistant to prior immunotherapies. This study presents the design, synthesis, and evaluation of novel bimodular conjugate molecules combining telomere-targeting nucleoside analogs and phosphatidyl diglyceride groups. Among them, dihexanoyl-phosphatidyl-THIO (diC6-THIO) showed high anticancer activity with sub-µM EC50 values in vitro across various cancer cell lines. In mouse colorectal cancer models, diC6-THIO demonstrated strong anticancer effects alone and in combination with PD1/PD-L1 inhibitors. Administration of this compound resulted in the efficient formation of Telomere dysfunction Induced Foci (TIFs) in vitro, indicating an on-target, telomerase-mediated telomere-modifying mechanism of action for the molecule. Systemic treatment also activated CD4+ and CD8+ T cells while reducing regulatory T cells, indicating immune system enhancement. These findings highlight diC6-THIO as a promising telomere-targeting prodrug with dual effects on telomere modification and immune activation.