Preface

This book provides a comprehensive overview of drug repurposing as well as its role in developing drugs for infectious diseases. These drugs include antivirals and antibacterial and anticancer drugs, and several immunotherapeutics. It highlights recent advancements as well as future directions for effective utilization of drug repurposing. Due to the high costs and time associated with the new drug discovery process, the inclination towards drug repurposing is increasing for common as well as rare diseases. The book covers various aspects and features of drug repurposing, which is crucial for promptly identifying drugs of choice for communicable and non-communicable diseases.

Drug repurposing (also known as drug repositioning, reprofiling, or re-tasking) is a drug discovery strategy for identifying new uses for already approved or investigational drugs that are not envisaged by the original medical indication. The drug repurposing approach has numerous advantages over new drug discovery. The most important is the reduction of risk of failure due to the available safety data of the repurposed drugs. Another important aspect of drug repurposing is that the time frame required for the development of drugs can be reduced due to available preclinical safety assessments. Moreover, the investment is less in the case of repurposed drugs. However, the regulatory and phase 3 trial costs may be similar to those of new drugs. Importantly, the cost for repurposed drugs to come to the market is estimated to be US\$300 million in comparison with the estimated cost of US\$2-3 billion for new drug discovery.

This book discusses research methodologies, resources, and technologies for identifying molecular aspects and therapeutic applications of drug repurposing for various communicable and non-communicable diseases. Within the frame of drug discovery, the book includes seven chapters, each of which focuses on a specific aspect of drug repurposing. This book is a self-contained collection of scholarly contributions targeting an audience of practicing researchers, academics, Ph.D. students, and other scientists.

I am overwhelmed in all humbleness and gratefulness to acknowledge all the contributors who trusted me and supported me in this work. I am especially thankful to Dr. Raymond Chang (Institute of East-West Medicine, New York, USA) and Dr. Angus Dalgleish (St. Georges, University of London, London, UK) for providing excellent assistance in editing Chapters 9–11 on drug repurposing for anticancer drug discovery. My research fellows and students are central to all my research and academic work. They are the motivating force behind anything constructive I do. They are truly brilliant and have a bright future. I would like to express our special thanks to our mentors, teachers, and students who gave me the strength to see this project to fruition. Also, I would like to thank the

colleagues, family, and friends who provided encouragement and support. A happy environment at home is essential for any kind of growth, and I thank my family, especially my talented wife and children, for the same.

> **Dr. Shailendra K. Saxena** Professor, Center for Advanced Research (CFAR), Faculty of Medicine, King George's Medical University (KGMU), Lucknow, India

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Section 1

Drug Repurposing

for Infectious Diseases

Section 1
