Anti-PD-L1 nanobody guided in situ self-assembly and release of IOX1 and FDU for enhanced cancer chemo-immunotherapy

The clinical outcomes of immunotherapy are limited by the immunosuppressive tumor microenvironment (TME) and immune-related adverse effects. To address these issues, here we develop a tumor-specific chemo-immunotherapy prodrug FDU-IOX1-FF-Nb for highly-effective and low-toxic cancer therapy. This prodrug incorporates fluorouracil (FDU) to induce immunogenic cell death and reshape the TME, while the checkpoint inhibitor 5-carboxy-8-hydroxyquinoline (IOX1) provides immune checkpoint blockade (ICB) treatment and inhibits the expression of P-glycoproteins to overcome drug resistance. Furthermore, a small-sized anti-PD-L1 nanobody selectively delivers the prodrug to PD-L1 overexpressing tumor cells and blocks the PD-1/PD-L1 pathway for improved ICB treatment effect. The prodrug self-assembles into large nanoparticles within tumor cells via the π-π stacking interaction between FF after the reduction of glutathione, accumulating and preserving the drugs in the tumor sites. Finally, the esterase that are highly expressed in tumor cells cleave the ester bonds on nanoparticles, releasing free IOX1 and FDU for the chemotherapy and immunotherapy. Through the process of PD-L1 targeting, glutathione-triggered self-assembly, and esterase-mediated release of IOX1 and FDU, efficient cancer chemo-immunotherapy and precise tumor suppression with minimal non-target toxicity are achieved.