In a phase I safety clinical trial, 15 children with relapsed or refractory medulloblastomas that did not respond to other treatments received different doses of an antibody called TB-403, which targets a protein expressed in these cancers. Although treatment was safe, there were no tumor regressions. However, most of the patients experienced stabilization of their disease -- i.e., stoppage of progression -- which persisted for more than 100 days in four patients.