Targeting β-catenin and PD-L1 simultaneously by a racemic supramolecular peptide for the potent immunotherapy of hepatocellular carcinoma

Objective: The low clinical utility of immune checkpoint inhibitors (ICIs) against PD-1 or PD-L1 has recently been associated with the activation of the Wnt/β-catenin signaling pathway in hepatocellular carcinoma (HCC), which promotes tumor immune escape and resistance to anti-PD-1/PD-L1 therapy. Hence, we aimed to fabricate a supramolecular peptide which could target the Wnt/β-catenin signaling pathway coupled with ICIs blockage therapy for optimizing HCC immunotherapy. Methods: A racemic spherical supramolecular peptide termed sBBI&PDP nanoparticle was constructed by hierarchical self-assembly, comprising an L-enantiomeric peptide as an inhibitor of BCL9 and β-catenin (sBBI) and a D-enantiomeric peptide as an inhibitor of PD-1/PD-L1 (PDP). Results: sBBI&PDP nanoparticle potently suppressed the hyperactivated Wnt/β-catenin signaling pathway in vitro and in vivo, while blocking endogenous PD-L1 effectively. Furthermore, sBBI&PDP increased the infiltration and action of CD8(+) T cells at tumor sites. Notably, compared with the original sBBI and commercial Anti-PD-L1 inhibitors, the designed sBBI&PDP showed stronger antitumor efficacy in an orthotopic homograft mice model of HCC and a PDX HCC model in Hu-PBMC-NSG mice. Moreover, sBBI&PDP possessed a favorable biosafety profile. Conclusion: The successful implementation of this strategy could revitalize ICIs blockage therapy and promote the discovery of artificial peptides for HCC immunotherapy.