Discovery of novel tumor-targeting peptide-oncolytic peptide based conjugates (PPCs): A new paradigm for targeted...

Oncolytic peptides, which possess synergistic oncolytic-immunotherapy effects, have exhibited advantages including unique anticancer mechanism, overcoming drug resistance and broad anticancer spectrum in clinic. Nevertheless, conventional oncolytic peptides often suffer from poor stability, limited efficacy, and moderate anticancer selectivity. In this study, the stability-, potency-, and selectivity-guided optimizations were conducted on the first-in-class oncolytic peptide Clip-71. The robust synthetic strategy, in vitro and in vivo anticancer activity, and anticancer mechanism especially immune activation ability were systematically investigated for obtained peptides. The first round of stability-guided optimization identified the mirror-image peptides represented by QY-8, which possessed strikingly high stability, as well as outstanding in vitro and in vivo anticancer activities. Subsequently, to address the limited selectivity and nonspecific distribution of oncolytic peptides, the second round of selectivity-guided and PPCs-strategy based optimization was conducted on QY-8. Strikingly, the novel PPC QY-13, which was obtained through conjugation of the SSTR2-targeting peptide Tyr³-octreotate to QY-8, exhibited most potent anticancer activities both in vitro and in vivo, enhanced immunostimulatory activity, and superior biosafety as well as tumor targeting potency. Collectively, this study not only established promising strategies to significantly improve the anticancer potential of cytotoxic peptides, but also provided the new paradigm for targeted oncolytic-immunotherapy.