In Silico Design of a Humanized Chimeric Arginine Deiminase ABSTRACT Arginine deiminase (ADI) is a bacterial enzyme with promising therapeutic potential for the treatment of arginine-auxotrophic cancers such as hepatocellular carcinoma, melanoma, and mesothelioma. ADI exerts its antitumor effect by depleting extracellular arginine, an amino acid essential for the survival of certain tumor cells lacking argininosuccinate synthetase expression. Despite its therapeutic promise, the bacterial origin of ADI leads to high immunogenicity, which may trigger immune responses, reduce enzyme efficacy, and limit repeated administration. This project aims to design a humanized chimeric ADI in silico by identifying immunogenic epitopes in bacterial ADI and substituting them with structurally analogous regions from the human arginine-metabolizing enzyme while preserving catalytic function. Structural modeling, immunogenic epitope prediction, molecular docking, and protein validation analyses will be performed to evaluate the stability and substrate-binding ability of the engineered chimera. The resulting humanized ADI is expected to exhibit reduced immunogenicity while maintaining therapeutic activity, providing a potential strategy for improving enzyme-based cancer therapies.