A disease is defined as rare if the prevalence is fewer than 200, 000 in the United States. It is estimated that there are more than 7, 000 rare diseases, which collectively affect 30 million Americans or 10% of the US population. This diverse and complex disease area poses challenges for patients, caregivers, regulators, drug developers, and other stakeholders. This book is proposedto give an overview of the common issues facing rare disease drug developers, summarize challenges specific to clinical development in small populations, discuss drug development strategies in the evolving regulatory environment, explain generation and utilization of different data and evidenceinside and beyond clinical trials, and use recent examples to demonstrate these challenges and the development strategies that respond to the challenges.Key Features:* Rare disease.* Drug development.* Innovative clinical trial design.* Regulatory approval.* Real-world evidence.