This book provides an overview of the essential characteristics and clinical applications of therapeutic proteins against human diseases, including cancers, immune disorders, infections, and other diseases. It presents the latest advancements in protein engineering techniques for producing desirable therapeutic proteins. The book also covers the strategies used to formulate and deliver systemic therapeutic proteins, approved protein therapeutics and their targets, and pharmacogenetic biomarkers. Further, it discusses challenges associated with the clinical implications of therapeutic proteins, including safety, immunogenicity, protein stability, degradation, and efficacy. It illustrates the development of biosimilar antibodies, optimization strategies for producing biobetter antibodies, and presents fundamental concepts about biosuperior therapeutics. Lastly, it includes a discussion about protein-based vaccines against bacterial and viral infections.