David Biggerstaff, MHA
President
David Biggerstaff began his career at Riley Children’s Health on Monday, Feb. 3, 2025. He brings a wealth of experience and a strong record of accomplishments in healthcare leadership to the IU Health team. He is a seasoned executive with extensive experience in both adult and pediatric academic medical centers, as well as community-based programs and facilities. His leadership emphasizes fostering a culture of excellence, enhancing research and clinical programs and implementing performance management systems to improve quality, service, employee engagement and philanthropy outcomes.
Since 2022, he served as chief operating officer at Intermountain Health’s Saint Joseph Hospital in Denver, where he oversaw all service lines and clinical operations, including real estate and facility planning, physician contracting and strategic relationships. Before that, he was enterprise executive vice president and chief operating officer at Children’s Colorado for six years where his responsibilities included all aspects of nursing, clinical support and operations across four hospital campuses, including patient care services, ambulatory operations, facilities planning, professional and support services as well as performance improvement and accreditation.
Biggerstaff also served as president and chief operating officer at Children’s Medical Center of Dallas for nine years in a number of leadership roles. He was awarded “Top C-Suite Executive” by the Denver Business Journal for leadership accomplishments throughout the COVID-19 pandemic.
He holds a master’s degree in healthcare administration from Trinity University in San Antonio, Texas, and completed an administrative residency at INTEGRIS Health in Oklahoma City. He has a bachelor’s degree in business administration with an emphasis in accounting from Oklahoma State University.
Mara Nitu, MD
Vice President and Chief Medical Officer
Mara Nitu, chief medical officer, oversees clinical hospital operations and physician and APPs integration and creates an exceptional practice environment to ensure optimal patient outcomes.
Nitu joined the Department of Pediatrics at Riley Children’s Health in 2001. She previously served as Pediatric Lifeline’s medical director, PICU’s medical director and the Division of Pediatric Care’s division chief. She was vice chair of Clinical Affairs for the Department of Pediatrics and ACMO at Riley Children’s, engaging in clinical operations, statewide expansion, mentorship and professional development. Since 2018, she has led clinical effectiveness work and engaged Riley’s medical director team to eliminate waste and increase value.
A Carol Davila University of Medicine and Pharmacy graduate, she completed her residency at State University of New York at Stony Brook and fellowship at the University of Cincinnati. She is currently a professor of Clinical Pediatrics at Indiana University School of Medicine.
Simmy King, DNP, MBA, RN, NE-BC, FAAN
Vice President and Chief Nursing Officer
Simmy King serves as vice president and chief nursing officer for Riley Children's Health. In this role, she is responsible for advancing nursing practice, quality outcomes, and professional development across the organization while leading a long-term nursing strategy. She works closely with nursing and interdisciplinary leaders to foster a culture of excellence, innovation, and compassionate care for children, moms and families.
King joined Riley Children's Health in 2026 from Children's National Hospital in Washington, D.C., where she served as director of Nursing Education and Professional Development. There, she led digital technology and nursing education strategies designed to prepare nurses for a dynamic, technology-enabled healthcare ecosystem. Throughout her career, King has demonstrated a strong commitment to cultivating resilient nursing cultures and supporting professional growth among nursing teams.
A nationally recognized nursing leader, King has served on the boards of the American Organization for Nursing Leadership, the Virginia Organization for Nursing Leadership and the D.C. Board of Nursing. She currently serves as a commissioner on the American Nurses Credentialing Center Commission on Magnet and as a member of the American Academy of Nursing's determinants of health policy standing committee.
King earned her Doctor of Nursing Practice degree from George Washington University, her Master of Business Administration from the University of Maryland, her Master of Science, Healthcare Administration from the University of Maryland and her nursing degree from the University of Toronto. She is board-certified as a nurse executive and a Fellow of the American Academy of Nursing (FAAN), one of the profession's highest honors recognizing leadership and contributions that advance nursing policy and practice.
Vanessa Roshell-Stacks, MHA
Vice President and Chief Operating Officer
Vanessa Roshell-Stacks brings more than 25 years of healthcare leadership experience with a strong focus on operational efficiency, patient flow, decision support and revenue cycle management. She began her career providing therapy for autistic children and has since held senior leadership roles across premier healthcare institutions.
Most recently, Vanessa served as Vice President of Ancillary and Support Services and Site Administrator at UCSF Benioff Children’s Hospitals in Oakland, California. In this role, she oversaw a broad portfolio spanning support services, clinical ancillary departments, supply chain, emergency management, safety, regulatory compliance, facilities/design and construction.
Prior to UCSF, she was Vice President of Operations and Care Transition at Rush University Medical Center in Chicago, where she directed multi-departmental operations for the 700-bed-academic medical center, including the transfer center hub, care coordination across the system, and patient flow activities and improvements. Earlier in her career, she held leadership positions across health systems, in both Atlanta and Augusta, Georgia, South Carolina, and Alabama consistently driving improvements in operational effectiveness and care delivery.
Vanessa holds a Master of Health Administration and Bachelor of Science in Experimental Psychology and Business Administration from the University of South Carolina, along with additional studies in Molecular and Cellular biology from the University of Michigan.
Frank Runion
Vice President and Chief Financial Officer, Metro Region
As chief financial officer for Riley Children’s Health, Frank Runion directs the financial operations and strategic financial planning for Riley Children’s and its pediatric service line. He oversees the budget, financial analysis and planning, capital management and workforce contract management.
Runion has been with Indiana University Health for over 20 years. Prior, he worked at St. Vincent Health and Wishard Health Services (now Eskenazi Health). He has over 30 years of healthcare and financial experience.
With a bachelor’s degree in accounting from Anderson University, he is a certified public accountant and a member of the Children’s Hospital Association, CFO Forum. Runion also serves on the Board of the Indiana Burn Camp and is the treasurer of his church.
Douglas K. Graham, MD, PhD
Physician-in-Chief, Riley Children's Health
Chair, Department of Pediatrics, Indiana University School of Medicine
Douglas K. Graham, MD, PhD, serves as physician-in-chief for Riley Children's Health and chair of the Department of Pediatrics at Indiana University School of Medicine. In these roles, he provides strategic leadership for pediatric clinical care, research and academic programs, working alongside physicians, researchers, learners and care teams to advance outcomes for children and families while strengthening Riley's position as a national leader in pediatric medicine.
Dr. Graham joined Riley Children's Health in 2026 from Children's Healthcare of Atlanta and Emory University School of Medicine, where he served as chief of the Aflac Cancer and Blood Disorders Center and chief of the Division of Pediatric Hematology, Oncology and Bone Marrow Transplant. He led one of the nation's largest pediatric hematology and oncology programs, overseeing growth across faculty recruitment, clinical services and research while advancing programs that integrate patient care, education and scientific discovery.
A nationally recognized pediatric oncologist and physician-scientist, Dr. Graham is a leader in pediatric leukemia, cancer therapeutics and translational research. He has served as president of the American Society of Pediatric Hematology/Oncology, held leadership positions within the Children's Oncology Group and was elected to both the American Society for Clinical Investigation and Association of American Physicians. Dr. Graham leads an NIH-funded laboratory focused on identifying and advancing novel therapeutic targets for pediatric cancers. His research has helped move discoveries from the laboratory into early-phase clinical trials supporting the development of new treatment options for children.
Dr. Graham earned his medical degree and doctorate from University of North Carolina. He completed residency and fellowship training at Colorado Children’s.
Mark Cain, MD, FAAP
Vice President and Surgeon-in-Chief
Dr. Cain returns to Riley Children’s as Surgeon-in-Chief. He is also a Professor of Urology at the Indiana University School of Medicine.
Dr. Cain graduated from medical school at Oregon Health Sciences University in 1987. He completed his residency in Urology at Albany Medical Center, followed by a two-year fellowship in Pediatric Urology at the Mayo Clinic.
He was a faculty member at Georgetown University for two years, then spent the next 23 years at Riley Hospital for Children and the Indiana University Department of Urology. He served as the Robert Garrett Professor of Urology and Chief of Pediatric Urology until moving to Seattle where he was Associate Surgeon in Chief, Director of Regional Surgical Services, and Director of Surgical Ambulatory Care for Seattle Children’s Hospital from 2019-2023.
His primary clinical interests are surgical reconstruction of congenital anomalies of the genitalia, complex lower urinary tract reconstruction, management of prenatal urologic abnormalities, and surgical management of urinary tract obstruction. Dr. Cain has published nearly 300 articles and book chapters and lectured internationally regarding various topics in pediatric urology, but with a focus on both long-term and patient-centered outcomes of urologic reconstruction.
Dr. Cain is a trustee on the American Board of Urology and serves as the liaison for the examination committee and chair for pediatric urology specialization, and is president elect for the ABU in 2025. He is a past chair for the Section on Urology of the American Academy of Pediatrics, and the Society for Fetal Urology.
Dr. Cain is a native of the Pacific Northwest, growing up in Willamette Valley’s Sherwood, Oregon. He is married to Charla Cain, has three married adult children and two grandchildren.