His clinical and research interests are primarily focused on development of methods to induce immunological tolerance in organ transplantation. He was the first to report a consistent model for induction of renal allograft tolerance in nonhuman primates through a mixed chimerism approach. This and subsequent pre-clinical reports have extended this approach to the world’s first clinical trials for induction of renal allograft tolerance in HLA mismatched kidney transplantation. This is a seminal achievement of a clinical protocol leading to the first reproducibly successful induction of renal allograft tolerance in humans and was reported in the New England Journal of Medicine in 2008 and 2013. He was awarded the Martin Research Prize at MGH in 2009 and the New Key Opinion Leader Award by the Transplantation Society in 2010 for this work.

Most recently, he was appointed an inaugural director of the MGH Legorreta Center for Clinical Transplantation Tolerance, which was built to become the world’s leading center dedicated to preventing organ rejection after transplant surgery without the use of lifelong immunosuppression.

In the field of xenotransplantation, he has collaborated extensively with eGenesis over the past five years, achieving over two years of survival for genetically edited kidney xenografts in nonhuman primates, which was published in Nature in 2023. In March 2024, he successfully performed the world first kidney xenotransplantation from the pig with 69 genomic edits in a living patient with end stage renal disease.