Development of a novel targeting antimicrobial peptide conjugate for selective membrane disruption in non-receptor-targetable cancer cells

Introduction: Chemotherapy remains a cornerstone in cancer treatment, but its non-selective toxicity to normal cells often leads to severe adverse effects. Targeted ligand-drug conjugates(TDCs) have emerged as promising alternatives to improve therapeutic specificity. Conventional TDCs rely on overexpressed surface proteins in tumour cells, limiting their applicability. In this study, we present a novel TDC strategy employing antimicrobial peptides(AMPs) as cytotoxic payloads to selectively disrupt cancer cell membranes without the need for specific intracellular targets. <br/><br/>Methods and Results: Compound 174-3 is a structure-refined AMP derived from an amphibian temporin peptide (compound 111). Using compound 174-3 as potent cytotoxic payload tagged at the C-terminus with a protease-cleavable linker and PEG(n), we synthesised a peptide conjugate, namely compound 209. Compound 209 exhibited a much wider therapeutic window compared to it precursors, paclitaxel, etoposide, 5-fluorouracil and cisplatin. LDH release and Sytox Green uptake assays were performed to assess membrane disruption in both NCI-H460 cancer cells and normal cell lines (MRC-5, HEK-293, HMEC-1). At the IC50 concentrations, compound 209 induced 20%LDH release and 35% Sytox Green uptake in NCI-H460 cancer cells, with no significant effects on normal cells, while compound 111 and compound 174-3 caused considerable membrane damage in both cancer and normal cells, indicating that compound 209 exhibits significantly improved membrane selectivity. The antiproliferative effect of compound 209 was also confirmed in chemoresistant NCI-H460/R cells, where it retained significant activity. <br/><br/>Conclusion: This novel strategy of using AMPs in TDCs offers a promising approach for selectively targeting non-receptor-targetable cancer cells. Compound 209 demonstrated enhanced selectivity and retained activity in drug-resistant NCI-H460 variants, indicating its potential as a targeted therapeutic with reduced toxicity to normal cells. This approach could expand treatment options for heterogeneous tumours that evade receptor-dependent and traditional chemotherapy, helping to address the challenge of drug resistance in cancer treatment.