GZMB and glioblastoma: Studies have shown that successful ICI treatment is associated with increased cytotoxic CD8+ (granzyme-B+ or IFN-γ +) T-cells and reduced Tregs in the tumor.3,4 The first large clinical trial of ICI testing anti-PD-1 in recurrent GBM (CheckMate-143) found that there was a failure of anti-PD-1 (with or without combination anti-CTLA-4) to prolong overall survival compared to the control of bevacizumab.5,6 However, 3 studies found that that there is a positive T-cell response following anti-PD-1 treatment in GBM patients, and that altering the dosing schedule may provide better response.7–9