Project Summary Incidence of liver cancer has tripled since the 1980s, and it is currently the third leading cause of cancer- related deaths worldwide. The 5-year survival rate of advanced liver cancer is currently below 12%, indicating the poor prognosis of this malignancy. One reason for the poor outcome is the lack of effective therapies for HCC. Less than 2% of patients respond to sorafenib, the only FDA-approved drug for liver cancer. Given the increased incidence of liver cancer worldwide, there is an urgent need to develop improved therapies for HCC. Monoclonal antibodies represent an important group of targeted therapies that have been adopted in the treatment of most major cancer subtypes. However, the anti-EGFR antibody is minimally effective in liver cancer due to intrinsic resistance. One mechanism of drug resistance is the overexpression of fucose residues on the surface of liver cancer cells. Consequently, overexpression of a fucosylated protein is used clinically as a biomarker for liver cancer. Functionally, these fucose residues diminish the activity of the anti-EGFR antibody by promoting the hyperactivation of EGFR protein. The proposed research seeks to develop a targeted therapy for liver cancer by developing an antibody? enzyme conjugate. The anti-EGFR antibody will direct the fucosidase enzyme to liver cancer cells in order to cleave off fucose residues. Once the residues are cleaved, the antibody will efficiently inhibit EGFR-mediated cell proliferation, leading to cell death. Conjugates will be synthesized using established protocols and evaluated against a panel of liver cancer cells in vitro and in mice to determine their anticancer efficacy. In the short term, the antibody?enzyme conjugate will aid in elucidating the role of fucosylated glycans in mediating resistance to anti-EGFR therapies. The proposed study will also lead to the identification of a potent conjugate with markedly increased anticancer activity in liver cancer cells, providing crucial preclinical validation of this strategy. In the long term, the proposed work will have a significant impact in the development of the first effective targeted therapy for the management of liver cancer.