What We Do

We consistently enroll among the top 5% of all participating sites for clinical studies including NAFLD, NASH, MRSA, ABSSSI, pain, sepsis, community-acquired pneumonia, hospital-acquired pneumonia, diabetes, dermatology, vaccines, CV, influenza, and many others.

Through our corporate-wide commitment to research excellence, it is our goal to improve the process that will bring new medicines to our global community. We will settle for nothing less than changing the paradigm of clinical trials. We will do so by continuing to be on the progressive edge of efficient innovation to become the industry leader.

Meet Our Team

William O'Riordan, M.D. - Chief Medical Officer
J. Scott Overcash, M.D. - La Mesa Medical Director, Principal Investigator
Michael Waters, M.D. - Chula Vista Medical Director, Principal Investigator

Physicians/Principal Investigators

All clinical staff are trained and certified in Good Clinical Practice, the Health Insurance Portability and Accountability Act, and on the NIH Protecting Human Research Participants course.


William O'Riordan, M.D.

Chief Medical Officer, Medical Division

Dr. William O’Riordan, Chief Medical Officer, founded eStudySite in 1999 along with twelve healthcare providers with whom he’d performed research for over ten years. Dr. O’Riordan has been involved in emergency medicine for more than thirty years at St. Francis Medical Center, Paradise Valley Hospital and Sharp Chula Vista Medical Center. His academic appointments include Harbor General Hospital–UCLA Medical Center and UCSD. His nineteen years of clinical investigation has been performed at Paradise Valley Hospital and Sharp Chula Vista Medical Center. As Principal Investigator, he has directed over 70 studies including cSSSI, Stroke, Acute Myocardial Infarction, Unstable Angina, Sepsis, Septic Shock, Hospital & Community Acquired Pneumonia, Hepatitis C, Atrial Fibrillation, Congestive Heart Failure, Hyponatremia, Complicated Appendicitis, UTI/Pyleonephritis, Occluded Central Venous Access Devices, genomic studies and more. He has served as Chief of Staff at Paradise Valley Hospital and President of the American College of Emergency Physicians in California. Dr. O’Riordan has also served on numerous advisory adjudication committees including AstraZeneca, Basilea Pharmaceutica, Aventis Pharmaceuticals, Inc., Hoechst Marion Roussel among others. He is an examiner for the American Board of Emergency Medicine and a Fellow of the American College of Emergency Physicians. Dr. O’Riordan earned his medical degree from the University of Kansas Medical School and is licensed in Kansas and California.

J. Scott Overcash, M.D.
Medical Director-La Mesa, Principal Investigator
Dr. Overcash joined eStudySite in 2012 and is the Medical Director and serves as a Principal Investigator at our La Mesa site.  Dr. Overcash is a board certified Emergency Physician with over 10 years of clinical and research experience. He attended the University of North Carolina School of Medicine where he obtained his M.D. degree and completed their highly ranked Emergency Medicine residency program. Dr. Overcash is a Diplomate of the American Board of Emergency Medicine, a Fellow of the American Board of Emergency Medicine, board certified by the American Academy of Anti-Aging, and an active member of the Association of Clinical Research Professionals. His work has been published in national peer reviewed journals including the New England Journal of Medicine.
Michael Waters, M.D.
Medical Director-Chula Vista, Principal Investigator
Dr. Waters is the Medical Director and serves as a Principal Investigator at our Chula Vista site. Dr. Waters received his medical degree at UC Irvine School of Medicine, and is board certified in Emergency Medicine. His research experience includes, but is not limited to: pneumonia; skin infections; hepatitis; influenza; diabetes; and other infectious diseases.  He has clinical experience in general medicine including: pain management; cardiovascular diseases; and dermatology.