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.
He is a three-time cancer survivor of Hodgkin's Lymphoma. His treatment at Stanford University Medical Center while pursuing his Ph.D. led to discussions with colleagues about cancer treatments, which ultimately led to the discovery of "texaphyrin" molecules.