TGFB1 and glioblastoma: 102, 103. Currently, several trials are conducted with TGF-β inhibitors, some in combination with ICI, as preclinical findings have shown an increase in effector T cells in the tumor 103. PET imaging of TGF-β with the 89Zr-labeled antibody fresolimumab in patients with recurrent glioblastoma showed high tracer uptake in the tumor. This tumor type is known for high expression of TGF-β and its receptors 104. 89Zr-fresolimumab or other tracers visualizing TGF-β may enlighten resistance mechanisms to ICI therapy.