In this study INVENT4GB, DKTK scientists are investigating a new immunotherapy for glioblastomas, a particularly aggressive form of brain tumors. A T-cell therapy developed at the DKTK is being used here for the first time to treat patients with a relapse after radiochemotherapy. Here, the patient's own T-cells are taken and, with the help of a gene shuttle developed at the DKTK, the so-called S/MAR vectors, equipped with a T-cell receptor that recognizes and kills the tumor cells in a highly specific manner. The scientists identified and isolated this T-cell receptor targeting the tumor antigen PTPRZ1 in a previous vaccination study in glioblastoma patients. The T-cells equipped with the receptor in this way are then returned to the patients, on the one hand into the bloodstream, but also into the cerebrospinal fluid (CSF). The aim of this study is to test the safety of this completely new therapeutic approach as well as to clarify mechanisms of therapy response and therapy resistance on the basis of detailed molecular and cellular analyses of intratumoral immune responses after treatment.