Sadelain was previously the Steve and Barbara Friedman Chair, founding director of the Center for Cell Engineering, and the head of the Gene Transfer and Gene Expression Laboratory at Memorial Sloan Kettering Cancer Center.

[6] After obtaining his PhD in immunology at the University of Alberta in Edmonton, Canada, in 1989, he trained as a postdoctoral fellow at the Whitehead Institute for Biomedical Research, Massachusetts Institute of Technology (MIT) in Cambridge, Massachusetts.

[7] He is a past president of the American Society of Cell and Gene Therapy (2014–2015) and previously served on its board of directors from 2004 to 2007.

[8][9] Sadelain and his team study gene transfer in hematopoietic stem cells and T cells, the regulation of transgene expression, the biology of chimeric antigen receptors, and therapeutic strategies to enhance immunity against cancer.

Following the establishment of clinical CAR T cell manufacturing by Dr. Isabelle Rivière at MSK, Sadelain's team was the first to report on molecular complete responses induced by CD19 CAR T cells in adults with relapsed, refractory acute lymphoblastic leukemia.

His research with Dr. Prasad S. Adusumilli led to a collaboration with Atara Biotherapeutics, Inc. for a product candidate to treat malignant mesothelioma using mesothelin-targeted CAR T cells named icasM28z.

[23] The history of the field and Sadelain's contributions are narrated in the 2021 George Stamatoyannopoulos Memorial Lecture at the annual meeting of the American Society of Gene and Cell Therapy.