George Coukos, MD, PhD, is a physician-scientist whose career has focused on uncovering fundamental mechanisms in the tumor microenvironment (TME) that govern antitumor immunity, particularly through the function of tumor-infiltrating lymphocytes (TILs). He has held key leadership roles at the University of Pennsylvania, where he founded the Ovarian Cancer Research Center, and at the University Hospital of Lausanne and the Ludwig Institute, where he directs the Department of Oncology and the Ludwig Institute’s Lausanne Branch and leads a comprehensive program in cancer immunotherapy and cell therapy, bridging basic discovery and early-phase clinical development. Dr. Coukos’ discovery of spontaneous antitumor immunity in ovarian cancer helped overturn the dogma that most solid tumors are immunologically inert and catalyzed global research into T cell responses in cancer. His lab went on to characterize mechanisms of immune dysfunction in the TME, including suppression by the tumor vasculature. He was the first to describe the tumor endothelial barrier, showing that vascular cells actively regulate T cell infiltration—a finding that opened a new avenue of therapeutic targeting. His group has also identified key chemokine pathways essential for T cell trafficking, as well as tumor-intrinsic features that promote immune infiltration, including the role of tumor myeloid antigen-presenting cell niches and CD28 costimulation for effective T cell attack. These insights have informed new therapeutic strategies now undergoing clinical testing. Dr. Coukos efforts integrating mechanistic discovery, development and clinical translation have enabled the rational design and testing of neoantigen dendritic cell vaccines and personalized T cell therapies. His work continues to advance mechanism-driven immunotherapies for solid tumors.