Dr. Williams is the Senior Vice President and Chief Scientific Officer at Boston Children’s Hospital and Chief of Hematology/Oncology at Boston Children’s Hospital. He was a Howard Hughes Medical Institute Investigator for 16 years and his laboratory has been continuously funded by the NIH since 1986. He has trained over 45 fellows and post-doctoral fellows and numerous residents and medical students in his laboratory, the majority of which are still in academic medicine. 

He is a member of the National Academy of Medicine and has published over 250 peer-reviewed manuscripts and textbook chapters. He formerly served on the NIH Recombinant DNA Advisory Committee and Gene Therapy Safety Assessment Board. He is actively involved in gene therapy trials for immunodeficiency and neurological genetic diseases and has been the investigator, co-investigator or sponsor (IND holder) of multiple previous gene therapy trials and is sponsor or investigator of four current trials. He served as the Editor-In-Chief of Molecular Therapy from 2004-2009 and is co-founder of the Transatlantic Gene Therapy Consortium and the North American Pediatric Aplastic Anemia Consortium (NAPAAC).

His basic research has focused on hematopoietic stem cell biology, including genetic diseases of the blood and specifically molecular and biochemical analysis of the interaction between hematopoietic stem cells and the bone marrow supporting environment. His laboratory has significant experience in stem cell biology, hematopoiesis and gene correction and transfer techniques. His research has described the molecular basis for two rare immunodeficiency diseases due to mutations of RAC2 and RHOH, members of the RHO GTPase family of signaling molecules.

He has multiple patents of which two have been developed into FDA-approved drugs (Neumega™ and Retronectin™) and is co-founder of two biotech companies, Orchard Therapeutics and Alerion Biosciences. Dr. Williams is a past President of the International Society of Experimental and the American Society of Hematology.