The University of Vienna and the Faculty of Chemistry are deeply saddened by the passing of Professor Isaac P. Witz, who died on January 12, 2026, at the age of 91. The scientific community has lost a visionary immunologist and a cherished friend of the Viennese academic world.

Born in Vienna in 1934, Isaac P. Witz and his family were forced to flee the Nazi regime in 1939, emigrating to the British Mandate of Palestine. He earned his PhD from the Hebrew University of Jerusalem in 1965 and spent his distinguished career at Tel Aviv University. As a pioneer in the study of the tumor microenvironment, he was among the first to recognize that the tissue surrounding a tumor is crucial to its growth and the development of metastases.

Despite his experience of displacement, he remained deeply connected to Vienna. He maintained a close scientific collaboration with Professor Michael Micksche from early on, at a time when the Institute for Cancer Research was still part of the Faculty of Medicine at the University of Vienna. This partnership continued through the joint research cluster "Translational Cancer Therapy Research," a collaboration between the Institute of Inorganic Chemistry and the Center for Cancer Research. Throughout several visiting professorships—most recently in the winter semester of 2017/18 at the Faculty of Chemistry at the invitation of Dean Bernhard Keppler—he shared his expertise with Viennese students.

In recognition of his life's work and his contributions to science, the University of Vienna awarded him an honorary doctorate in 2018. In 2023, he was honored with the prestigious Szent-Györgyi Prize by the National Foundation for Cancer Research, and in 2024, the Medical University of Vienna appointed him Adjunct Professor at the Center for Cancer Research.

It is with deep sorrow that we accept the fact that a great friend and wonderful person has left us. We bow our heads in honor of Isaac. When we think of him, we remember his humanity, generosity, and open-mindedness. He dedicated his scientific life to studying the tumor microenvironment, an incredibly complex field. Together, we investigated molecular mechanisms characteristic of brain metastases—a major obstacle in clinical practice. He possessed a remarkable talent for distilling meaningful insights from vast amounts of molecular profiling data. Isaac always encouraged us to persevere, especially when faced with seemingly unsolvable problems. He remains a great role model for all of us.

In Isaac Witz, we lose a great researcher and a role model of humanity. His legacy will live on through his scientific contributions and the many colleagues he inspired.

Univ.-Prof. Christopher Gerner and emer. Univ.-Prof. Bernhard Keppler