Our Investigators


Thomas G. Ledbetter, M.D.

Medical Director and Investigator, Internal Medicine

Dr. Ledbetter provides physician oversight of all clinical operations. He also serves as an Investigator for adult studies, with interests focused on general health promotion and comprehensive management of chronic disease. Dr. Ledbetter received his Doctorate of Medicine from Louisiana State University School of Medicine and completed his training at Baylor University Medical Center at Dallas. He is board certified in internal medicine and has been practicing medicine for over 30 years. Dr. Ledbetter currently serves as the Chief Medical Officer at Baylor Scott and White Medical Center Waxahachie. He has a heart for the local community and is recognized for the excellent and compassionate care he provides. 

"Clinical research is a core value of the healthcare system. We must continue to better understand the basic science of diseases while looking for safer, more effective treatment for these illnesses. ClinPoint Trials now provides another community resource to expand the scope of healthcare in our community."

- Dr. Thomas Ledbetter

Photo Credit:  Mitya Ku

Peggy Linguist, M.D.

Investigator, Pediatrics

Dr. Linguist serves as an Investigator for pediatric studies. She received her Doctorate of Medicine from University of Texas Health Science Center San Antonio and completed her Pediatric internship and residency at the University of Tennessee, LeBonheur Children's Hospital in Memphis Tennessee. Dr. Linguist is a founding member of The HOPE Clinic, a healthcare facility providing care to the medically under-served in Ellis County. Dr. Linguist has been practicing pediatric medicine for 20 years and is beloved by her patients, their families, and the local community.

"Advancement of medicine through safe, responsible, and controlled clinical trials is beneficial for all of us, especially our children, grandchildren, and great-grandchildren. ClinPoint is committed to working together for the advancement of medicine. To me, "together" means our community investing in its future. The questions that are answered today through quality clinical trials will be the foundation that informs our future physicians and providers, so that they can, in turn, take the best care of our future generations."

- Dr. Peggy Linguist


Ammar Haque, M.D.

Investigator, Nephrology and Internal Medicine

Dr. Haque serves as an Investigator for adult studies conducted at ClinPoint Trials. He received his Doctorate of Medicine from the University of St. Eustatius Medical School and completed his residency and fellowship training in Nephrology at the Medical College of Wisconsin and its affiliated hospitals.  Dr. Haque is board certified in internal medicine and nephrology. In addition to practicing at Dallas Renal Group, he currently serves as the Chief of Nephrology at Baylor Scott and White Medical Center in Waxahachie and the Medical Director of Dialysis Services at Liberty Dialysis in Waxahachie. Dr. Haque has been in practice for over 10 years and is recognized for excellent and sincere care.



James Pickens, M.D.

Investigator, Family Medicine

Dr. Pickens serves as an Investigator at ClinPoint Trials. He received his Doctorate of Medicine from University of Texas Medical Branch at Galveston and completed his family medicine residency at Texas Tech Health Science Center in Lubbock. Dr. Pickens is board certified in family medicine. He not only owns a private practice, but also serves as a Hospitalist at Baylor Scott and White Medical Center Waxahachie. Dr. Pickens has been practicing family medicine for over 30 years and is known for his genuine care for his patients throughout their lifetime.


Our Staff


Sherry Johnson, RN, BSN, CCRA

Site Director

Sherry provides clinical research expertise that is rarely found at a research site. She received her nursing degree from University of Texas at Arlington and has over 18 years of nursing and clinical research experience. She has maintained certification as a Clinical Research Associate through the Association of Clinical Research Professionals (ACRP) since 2006. Her experience includes over 10 years of working directly with sponsor companies in clinical trial management. Her knowledge and leadership are a gateway to provide top-quality services to both our patients and sponsor clients. Sherry has been married for over 25 years and has three children. She loves to spend time with her family, is involved in her local church, and occasionally wishes herself away to the beaches of Florida.