Discovery of novel and highly potent XIAP-targeted peptide inhibitors using virtual screening

Lung cancer, a globally prevalent fatal malignancy, remains a major therapeutic challenge. X-linked inhibitor of apoptosis protein (XIAP) is overexpressed in various cancers, driving uncontrolled proliferation, while its specific inhibition suppresses tumour growth. Through virtual screening, we identified five novel candidate peptides (Peptides 1-5) with picomolar-level inhibitory activity. Peptide-5 showed the highest binding affinity (Kd = 10.2 ± 0.5 pM), and FP assay indicated that Peptide-5 competitively binds the BIR3 domain of XIAP against caspase-9. Molecular dynamics simulations confirmed the structural stability of its complex with XIAP. Meanwhile, Peptide-5 showed good serum and metabolic stability, as well as favourable cellular permeability. Notably, Peptide-5 exhibited potent antiproliferative activity against various tumour cells with no obvious toxicity to normal cells. Peptide-5 potentially activates apoptotic signalling through modulating the Bcl-2/Bax mRNA expression. In summary, our study confirms that Peptide-5 is a highly potent and promising XIAP-targeted inhibitor for the treatment of cancer.