Roger Hajjar is the director of the Gene and Cell Therapy Institute at Mass General Brigham.

He received his BS in Biomedical Engineering from the Johns Hopkins University in  and his MD from Harvard Medical School and the Harvard-MIT Division of Health Sciences & Technology. He completed his training in internal medicine, cardiology, heart failure/cardiac transplantation and research fellowships at Massachusetts General Hospital in Boston where he then directed the Cardiology Laboratory of Integrative Physiology and Imaging. From 2007 to 2018, Dr. Hajjar was the Director of the Cardiovascular Research Center, and the Arthur & Janet C. Ross Professor of Medicine at Mount Sinai School of Medicine in New York. From 2019 to 2022, Dr. Hajjar was head of R&D at Ring Therapeutics, a Flagship Pioneering company.

Dr. Hajjar is an internationally renowned scientific leader in the field of cardiac gene therapy. His laboratory had validated a number of cardiac targets  that led to the initiation and completion under his guidance of First-in-Human gene therapy trials in patients with heart failure.

He has authored over 500 publications and has received numerous awards for his achievements in the field cardiac gene therapy including the Young Investigator Award of the American Heart Association, the Doris Duke Clinical Scientist award, the Distinguished Alumnus Award from Johns Hopkins University, the American Heart Association Distinguished Achievement Award and the Thomas W. Smith Award of the American Heart Association.

He is the founder of multiple gene therapy companies, some of which have had successful exits.