Our Team
Kathryn Hassell, MD
Director and Professor
Dr. Hassell has been the Director of the Center since 2003, after serving as its Associate Director since 1992. She has been with the University since 1989. Dr. Hassell provides inpatient and outpatient care to adults with sickle cell disease at the University of Colorado Hospital. She is a site principal investigator for multi-center clinical trials for adults with sickle cell disease, and has provided national leadership on study steering and executive committees.
Dr. Hassell has led several regional projects through the Mountain States Genetics Regional Collaborative Center, and serves on the Newborn Screening Advisory Committee for the Colorado State Department of Health. She also sits on the steering committees of a number of national projects including the Sickle Cell Disease Treatment Demonstration Project for HRSA, the American Society of Hematology’s Public Health Taskforce, and the Registries and Surveillance for Hemoglobinopathies (RuSH) Project for the CDC and NIH.Dr. Hassell recently completed a four-year, part-time, IPA assignment with the National Heart, Lung and Blood Institute (NHLBI).
Rachelle Nuss, MD
Associate Director and Professor
Dr. Nuss has been with the University since 1988. She directs the pediatric program of the Colorado Sickle Cell Treatment and Research Center at The Children’s Hospital in Denver and conducts outreach clinics in Colorado Springs.
Dr. Nuss is a site principal investigator for multi-center clinical trials for children with sickle cell disease; she has led investigator-initiated translational and early phase clinical studies, and collaborates with basic science investigators.
Christopher McKinney, MD
Associate Professor
Dr. McKinney has been caring for patients with sickle cell disease at Children's Hospital Colorado since 2012. He became the Director of the Pediatric Sickle Cell and Hemoglobinopathy Program in 2022.
Dr. McKinney clinical focus includes providing comprehensive medical care for patients with sickle cell disease and other hemoglobinopathies from birth until transition to adulthood including provision of curative therapy options including allogeneic hematopoietic stem cell transplant and autologous gene therapy.
He is the local Principal Investigator for several clinical trials for patients with sickle cell disease. He is interested in medical education and serves as the Assistant Course Director for the School of Medicine Hematology course for first year medical students.
Gemlyn George, MD
Assistant Professor
Gemlyn George, MD has been an Assistant Professor with the Division of Hematology at the University of Colorado Anschutz Medical Center since 2021. Dr. George provides treatment to adults with sickle cell disease at the University of Colorado Hospital.
Dr. George started his research career studying the gut microbiome and during Fellowship worked closely with Investigators at the Blood Center of Wisconsin and the Center for International Blood and Marrow Transplant Research (CIBMTR).
Dr. George is currently an Investigator at the Colorado Sickle Cell Treatment and Research Center and is actively involved in multi-center clinical trials and translational research for adults with sickle cell disease.
| Center Personnel | Title | Contact Information |
| Kathryn Hassell, MD | Director and Professor Adult Hematologist | 720-848-0300 Clinic / Patient Needs 720-848-4017 Clinic FAX Number 303-724-9070 Center Administration |
| Gemlyn George, MD | Assistant Professor Adult Hematologist | 720-848-0300 Clinic / Patient Needs 720-848-4017 Clinic FAX Number 303-724-9070 Center Administration |
| Rachelle Nuss, MD | Associate Director and Professor Pediatric Hematologist | 720-777-6740 Clinic / Patient Needs 720-777-7230 Clinic FAX Number 303-724-9070 Center Administration |
| Christopher McKinney, MD | Associate Professor Pediatric Hematologist | 720-777-6740 Clinic / Patient Needs 720-777-7230 Clinic FAX Number 303-724-9070 Center Administration |
| Theresa M. Martinez, BA | Center Administrator Finance and Business | 303-724-9070 Center Administration |
| Michael Regier, MSW, LCSW | Transition Program Coordinator | 303-724-9066 Office |
| Julie McAfee, BS | Clinical Research Coordinator | 303-724-9072 Office Julie.McAfee@cuanschutz.edu |
| Donna Holstein, RN, BSN | Coordinator and Clinical Educator Newborn Screening Follow-Up Program | 303-724-9075 Donna.Holstein@cuanschutz.edu |