To Evaluate the Safety, Tolerability and Preliminary Efficacy of EU307

This study is testing a new drug called EU307 for people with advanced liver cancer (hepatocellular carcinoma, or HCC) that has not responded to previous treatments. EU307 is designed to target a protein called GPC3, which is overexpressed on certain liver cancer cells. The study is examining safety, tolerability, and early signs of effectiveness. **You may be eligible if:** - You are 19 years old or older - You have unresectable (inoperable) liver cancer confirmed by biopsy or imaging - Your cancer has progressed after or was not responsive to first- or second-line standard treatments (such as atezolizumab + bevacizumab, sorafenib, or lenvatinib) - Your tumor tests positive for the GPC3 protein - You have at least one measurable tumor that can be tracked **You may NOT be eligible if:** - Your cancer does not express the GPC3 protein - You have no standard treatment options available and your health cannot support experimental therapy - Your organ function or performance status is too poor for treatment Talk to your doctor to see if this trial is right for you.