He is a three-time Hodgkin's Lymphoma cancer survivor. He was treated for cancer at Stanford University Medical Center during work on his Ph.D. Discussions with his colleagues regarding possible treatments eventually led to the discovery of so-called "texaphyrin" molecules, named as such due a semblance to the shape of the five-pointed star in the State flag of Texas.,10-Gallon Molecule Stomps Tumors  In 1996, Sessler described possible uses of these compounds in medicine in the Proceedings of the National Academy of Sciences journal.
As a cancer survivor of Hodgkin's Lymphoma, he experienced three rounds of treatment at Stanford University Medical Center during his Ph.D. research. These conversations with colleagues about potential therapies eventually led to the development of "texaphyrin" molecules.