Trained as a clinical hematologist in London UK he specialized in stem cell transplantation before moving to Washington DC in 1993 where he established the National Heart Lung Institute stem cell transplantation program at the National Institutes of Health Bethesda MD. Between 2018 and 2022 he was Director of the Stem Cell Transplantation and Cellular Therapy Program at the George Washington University Hospital in Washington DC.  

John Barrett is a pioneer of stem cell transplantation and has a lifelong expertise in treatment of blood diseases.  Dr. Barrett was elected a Fellow of the Royal College of Physicians in 1998. He served as President of the European Society for Bone Marrow Transplantation in 1983 and President of the American Society for Blood and Marrow Transplantation in 2010. He has received numerous honors including awards from the National Institutes of Health, the National Health Service UK and the 2016 award from the American College of Physicans for Science as it relates to Medicine. He has authored over 350 original scientific articles, and over 150 reviews, editorials and book chapters including 6 books. He was Editor in Chief for the journal Cytotherapy between 2001 and 2018 and is currently Editor in Chief of the British Journal of Haematology.