This book discusses the optimization of protein therapeutic products for treatment of human diseases. It is based on the fact that though numerous important therapeutic protein products have been developed for life threatening and chronic diseases that possess acceptable safety and efficacy profiles, these products have generally not been reexamined and modified for an improved clinical performance, with enhancements both to safety and efficacy profiles. Advances in protein engineering, coupled with greatly enhanced understanding of critical product quality attributes for efficacy and safety, make it possible to optimize predecessor products for clinical performance, thereby enhancing patient quality of life and with the potential for great savings in health care costs. Yet despite such knowledge, there is little movement towards such modifications. This book examines engineering protein therapeutic products such that they exhibit an optimal, not just an adequate, clinical performance profile.