This document describes how real-world data was used to help expand a clinical trial for a rare disease. Specifically: 1. Claims data was analyzed to identify patients diagnosed with the rare disease and their physicians, applying inclusion criteria like diagnostic tests and drug treatments. This sized the national patient population and located diagnosing/treating doctors. 2. Physicians were mapped to local hospitals to identify areas with high concentrations of relevant patients and doctors. 3. A density analysis identified the top 20 hospitals that could serve as potential new clinical trial sites based on clusters of physicians and their patient counts. This innovative use of real-world data provided new insights to strengthen the company's rare disease research program.