Pedro Castillo Jr., MD
Principal Investigator
Board Certified in Internal Medicine and Rheumatology
Dr. Pedro Castillo Jr. is the Principal Investigator and clinical leader at Dallas Research Institute, where he oversees all aspects of trial execution while also providing direct care to study participants. A double board-certified physician in Internal Medicine and Rheumatology, he completed his medical education and advanced training at UT Southwestern.
Dr. Castillo brings nearly a decade of clinical experience to his role, having practiced Internal Medicine since 2017 and Rheumatology since 2019. His hands-on understanding of complex, chronic diseases informs his patient-centered approach to research and care.
Inspired by the visionary legacy of the late Dr. Stephen Harrison, Dr. Castillo helped launch DRI in early 2024. His mission is rooted in advancing medicine through research, expanding access to clinical trials, and helping bring transformative treatments to the diverse populations of the Dallas–Fort Worth Metroplex.
With a focus on compassion, education, and scientific curiosity, he approaches each trial as an opportunity to advance knowledge and improve lives. He is a proud member of the American Medical Association and the North Texas Latin American Physician Association.
In his free time, Dr. Castillo enjoys spending time with his wife and two children, martial arts training, reading, games, and travel.
Miguel Brito
Research Coordinator
Nallyve Mata
Research Assistant
Osiris Carranza
Research Coordinator
Destiny Robinson
Operations Manager
Ana Lennard
Front Desk Office Associate
Ingrid Welch
Regulatory and Quality Associate
Our Founder
Stephen Harrison, MD, COL (Ret.)
Dr. Stephen Harrison was a pioneering force in liver disease research and the visionary behind Dallas Research Institute. A decorated U.S. Army Colonel and internationally recognized hepatologist, Dr. Harrison devoted over three decades to advancing the understanding and treatment of Metabolic Dysfunction-Associated Steatohepatitis (MASH).
Throughout his distinguished career, he led groundbreaking clinical trials, shaped global research standards, and authored over 350 peer-reviewed publications, helping to define the path forward for non-invasive diagnostics and pharmacologic therapies in MASH/MASLD.
Dr. Harrison believed in empowering patients, accelerating discovery, and building research centers that combined scientific excellence with community care. His leadership, mentorship, and relentless pursuit of progress continue to guide our work at DRI.
Though he is no longer with us, his legacy lives on in every study we conduct, every patient we serve, and every breakthrough we help bring to life. We are honored to carry his vision forward.
