PROJECT SUMMARY Hepatocellular carcinoma (HCC) is the 5th most common malignancy in the world and the 4th leading cause of cancer death in the US. Resection and transplantation are the sole potentially curative treatments for HCC, but only 10-15% of patients are candidates. Nivolumab (human anti-PD-1 mAb) was FDA approved in 2017 for HCC patients previously treated with sorafenib. Recent clinical trials demonstrate the potential of immune checkpoint blockade (ICB) antibodies against programmed cell death 1 (PD-1) and its ligand PD-L1 for the treatment of HCC. However, the immune suppressive tumor microenvironment (TME) of HCC leads to a resistance to ICB immunotherapy and immune related adverse effects (irAEs); thus, the efficacy of ICB immunotherapy may not be sufficient to elicit durable clinical benefits. Combinational ICB immunotherapies pairing with immunogenic local therapies are a promising approach for the treatment of HCC. Recently pre- clinic and clinical trials have tested aPD-L1 ICB immunotherapy in a combination with interventional local ablation therapies with the promise for enhancing overall therapeutic effects. One limitation that accounts for the compromised efficacy of systemic ICB immunotherapy in the combination is low tumor specific accessibility and off-target binding of ICB antibodies to normal tissues upon systemic administration. Tumor site specific delivery of ICBs will enhance tumoral immune checkpoint blockage efficacy with avoiding systemic non-specific activation of the immune system resulting in irAEs. Locally delivered ICB conjugated nano-carriers have enabled the emergence of platforms for safely delivering effective dose of ICBs in the tumor. We propose catheter-directed intra-arterial (IA) infusion of oriented anti-PD-L1 conjugated ferumoxytol using Z-domain (aPD-L1-Z-Fer) for a synergistic combination ICB immunotherapy with immunogenic irreversible electroporation (IRE) local therapy. An engineered Z domain, immunoglobulin G (IgG) Fc domain-specific binding protein, is proposed to enhance the immune checkpoint blocking efficiency of aPD-L1 with FDA approved iron oxide nanoparticles (ferumoxytol; Fer). Our recent results demonstrated that Z-domain adaptors provided a convenient and controlled aPD-L1 ICB conjugation onto Fer (aPD-L1-Z-Fer) and subsequent the enhancement of immune checkpoint blockade efficiency. Our proposed IA infusion of aPD-L1-Z-Fer will permit further efficient and targeted delivery of immunostimulatory aPD-L1 to allow an increase in the dosage and improved safety profile after the immunogenic interventional local ablation therapy for superior therapeutic outcomes. MRI visible aPD-L1-Z-Fer and MR image guidance should also permit to monitor/track/quantify the delivery of aPD-L1-Z-Fer to the targeted tumor tissues treated with an immunogenic local therapy. Through a collaborative project building upon our strengths in nano-immunotherapy, interventional oncology, and radiology, we seek to dev...