N-Substituted-2-(9H-Xanthen-9-yl)acetamide Derivatives Induce In Vitro Colon Cancer Cell Death via TASK-1 Inhibition: Lead Compounds for Further Optimization as TASK-1-Targeted Therapeutics in Colorectal Cancer.

Colorectal cancer (CRC) is the third most prevalent cancer globally. TASK-1, encoded by the KCNK3 gene, is emerging as a putative target in cancer; it regulates resting membrane potential, cell proliferation, and apoptosis. A series of 27 novel xanthene derivatives, modified at position 9, were synthesized via azide coupling of 2-(9H-xanthen-9-yl)acetohydrazide with selected amines and amino acids, followed by hydrazine-mediated conversion to the corresponding hydrazides. The cytotoxic activity of selected compounds (5a-5g, 6a-6h, 7b, 7f-7h) was evaluated against the HCT-116 cell line in vitro. In addition, molecular docking and molecular dynamics simulations were performed to investigate binding interactions and assess the stability of the protein-ligand complexes. Several compounds (5f, 5g, 6c, 6d, 6f, 6g, 7b, 7f, and 7h) exhibited moderate cytotoxic activity against HCT-116 cells (IC50: 66.97-99.62 µM), compared to cisplatin (IC50: 18.25 µM). Compound 7h demonstrated pronounced antiproliferative effects, evidenced by DAPI staining showing chromatin condensation and apoptotic body formation, along with a marked reduction in cell count and coverage. Molecular docking indicated favorable binding within the TASK-1 potassium channel, and molecular dynamics simulations confirmed the stability of the protein-ligand complex, with consistent interactions, including a key hydrogen bond with Asn240. These findings support 7h as a promising lead candidate. These findings identify xanthene-based derivatives as promising lead compounds for further optimization as TASK-1-targeted therapeutic candidates in colorectal cancer.